Development and Psychometric Validation of the OMFS-QoL-18: A Multidimensional Patient-Reported Outcome Measure for Postoperative Oral and Maxillofacial Surgery

Highlights

What are the main findings?

• The OMFS-QoL-18 demonstrated good internal consistency (Cronbach’s α = 0.789) and strong reproducibility (ICC = 0.81) in postoperative oral and maxillofacial surgery patients.
• Factorial analysis supported a multidimensional structure integrating respiratory comfort, sleep quality, daytime function, oro-maxillofacial performance, and global satisfaction.

What are the implications of the main findings?

• OMFS-QoL-18 provides a condition-specific, standardized tool for assessing patient-reported postoperative outcomes in oral and maxillofacial surgery.
• The instrument may enhance comparability across clinical studies and support patient-centered evaluation of surgical success.

Abstract

Background: Quality-of-life (QoL) assessment has become an essential component of outcome evaluation in oral and maxillofacial surgery (OMFS), particularly in interventions with functional implications for breathing, sleep, and oro-facial performance. Existing instruments often lack specificity for the postoperative OMFS population. This study aimed to develop and psychometrically validate the OMFS-QoL-18 questionnaire, a condition-oriented patient-reported outcome measure designed for postoperative assessment. Methods: A cross-sectional validation study was conducted on 226 adult patients evaluated 6–12 months after orthognathic or function-oriented OMFS procedures. Internal consistency was assessed using Cronbach’s alpha, and reproducibility using the intraclass correlation coefficient (ICC) based on a two-way random-effects model with absolute agreement. The internal structure of the instrument was explored through an exploratory dimensionality analysis using Principal Component Analysis (PCA), including Kaiser–Meyer–Olkin (KMO) testing and Bartlett’s test of sphericity. Descriptive statistics were calculated for item and domain scores. Results: The OMFS-QoL-18 demonstrated good internal consistency (Cronbach’s α = 0.789; standardized α = 0.783) and satisfactory reproducibility (ICC = 0.81; 95% CI: 0.74–0.87). The exploratory dimensionality analysis suggested a multidimensional structure, with five components explaining 67.1% of the total variance. Item clustering was broadly consistent with the predefined conceptual domains, including respiratory comfort, sleep quality, daytime function, oro-maxillofacial function, and global satisfaction. Given the use of PCA as a component-based method, these findings are interpreted as preliminary evidence of dimensional organization rather than confirmation of latent constructs. Conclusions: The OMFS-QoL-18 demonstrated good internal consistency and preliminary evidence of a coherent factor structure. These findings support its use as a promising condition-specific instrument, pending further validation studies. Further multicenter and longitudinal validation studies are warranted to confirm structural stability and responsiveness over time.

1. Introduction

Quality of life (QoL) has become a central outcome indicator in modern healthcare, particularly in surgical disciplines where treatment success extends beyond anatomical correction and functional restoration. In oral and maxillofacial surgery (OMFS), procedures frequently influence mastication, speech, swallowing, respiration, and facial aesthetics, domains that are intrinsically linked to psychological well-being and social interaction [1,2]. Consequently, postoperative evaluation should incorporate patient-reported outcomes alongside objective clinical parameters in order to capture the broader impact of surgical intervention.

QoL is widely recognized as a multidimensional construct encompassing physical, psychological, and social components of health. The World Health Organization defines quality of life as an individual’s perception of their position in life within the context of culture and value systems, and in relation to their goals and expectations [3]. This definition emphasizes the subjective dimension of health evaluation and supports the integration of patient-centered assessment tools into surgical outcome research. In OMFS, where functional rehabilitation often coexists with aesthetic modification, the translation of clinical improvement into daily life benefit is not always directly proportional and requires structured evaluation [4].

An increasing number of studies demonstrate that orthognathic and maxillofacial procedures have a substantial impact on patient-reported quality of life and overall well-being [5,6,7]. Improvements in facial harmony, occlusal function, and airway patency have been associated with enhanced self-esteem, reduced social anxiety, and better overall health perception [6,8]. In patients undergoing maxillomandibular advancement or other airway-oriented procedures, improved nasal airflow and sleep quality have been correlated with increased daytime energy and functional performance [9,10].

Despite these advances, the measurement of QoL in OMFS remains heterogeneous. Many studies rely on generic health questionnaires such as the SF-36 or oral-health-specific instruments such as the Oral Health Impact Profile (OHIP-14) [11,12]. Although these tools provide valuable information, they may not fully capture the specific postoperative profile of patients treated for dentofacial deformities, airway dysfunction, or combined functional–aesthetic indications. Disease-specific instruments, including the Orthognathic Quality of Life Questionnaire (OQLQ), have improved sensitivity for certain patient groups [13], yet they do not systematically address respiratory comfort, sleep-related symptoms, or postoperative oro-facial functional integration.

Recent systematic reviews emphasize the variability of QoL instruments used in head and neck and maxillofacial surgery and highlight the need for context-specific, psychometrically validated patient-reported outcome measures [14,15]. Moreover, the development of new instruments requires rigorous validation processes, including content validity, internal consistency testing, construct validity, and reproducibility, to ensure reliability and clinical relevance [16].

Given these considerations, the development of a dedicated QoL questionnaire tailored to postoperative OMFS patients is justified. A condition-oriented instrument may facilitate standardized outcome reporting, improve comparability between studies, and support evidence-based evaluation of surgical effectiveness from the patient’s perspective. The present study describes the development and psychometric validation of the OMFS-QoL-18 questionnaire, designed to assess health-related quality of life in patients undergoing oral and maxillofacial surgical interventions with functional impact on respiration, sleep, and oro-facial performance.

2. Materials and Methods

2.1. Study Design

The present study was designed as a cross-sectional observational investigation aimed at developing and psychometrically validating a patient-reported outcome measure intended to assess postoperative quality of life in individuals undergoing oral and maxillofacial surgical interventions with functional respiratory implications. The cross-sectional design was selected in order to evaluate patients’ perceptions at a defined postoperative interval, minimizing the influence of early healing variability while capturing relatively stable functional outcomes.

Data were collected during routine postoperative follow-up visits in a clinical setting. The study focused exclusively on the psychometric performance of the instrument, without evaluating clinical predictors of outcome or longitudinal changes.

2.2. Participants and Eligibility Criteria

Participants were recruited through convenience sampling from patients who presented for postoperative reassessment between six and twelve months after surgery. This time interval was deliberately chosen to allow completion of the acute postoperative recovery phase and functional adaptation, thereby providing a more reliable assessment of patient-perceived quality of life.

Eligible participants were adults aged 18 years or older who had undergone orthognathic surgery or oral and maxillofacial procedures performed with a functional objective, particularly interventions aimed at improving airway patency, respiratory function, or sleep-related breathing disturbances. Patients were required to be able to understand the content of the questionnaire and to complete it independently. All participants provided written informed consent prior to inclusion.

Patients were excluded if they were in the early postoperative phase, had undergone recent additional surgical interventions that could influence outcome perception, or presented neurological, psychiatric, or cognitive conditions that might compromise the reliability of self-reported responses. Questionnaires that were incomplete, incoherent, or methodologically invalid were excluded from analysis.

A total of 226 fully completed questionnaires met the inclusion criteria and were included in the final statistical analysis.

2.3. Development of the OMFS-QoL-18 Instrument

The OMFS-QoL-18 was developed through a structured, multistep process including conceptual framework definition, item generation, expert review, and item reduction.

First, the conceptual domains of the questionnaire were defined based on the clinical objectives and expected postoperative outcomes of oral and maxillofacial surgery, as well as on multidimensional models of health-related quality of life described in the literature. Particular emphasis was placed on domains that are frequently underrepresented in existing instruments, such as respiratory function, sleep quality, and daytime performance.

Second, an initial pool of items was generated by the research team based on recurrent postoperative concerns observed during routine clinical follow-up, together with a review of commonly assessed domains in existing quality-of-life instruments used in oral and maxillofacial surgery. This process resulted in a preliminary set of approximately 22 items covering the main domains of interest.

Third, the preliminary item pool underwent internal review by clinicians with expertise in oral and maxillofacial surgery. During this stage, items were evaluated for clinical relevance, clarity, redundancy, and domain coverage. Items considered overlapping, insufficiently specific, or potentially ambiguous were either reformulated or excluded.

Item reduction was performed iteratively, with the aim of achieving a balance between comprehensiveness and feasibility of administration. Priority was given to items that captured clinically meaningful and frequently reported patient concerns, while minimizing redundancy across domains.

This process resulted in the final version of the questionnaire, comprising 18 items grouped into five conceptual domains: nasal breathing and respiratory comfort, sleep and nocturnal breathing, daytime function and energy, oro-maxillofacial function and postoperative comfort, and global satisfaction.

The development process was primarily clinician-driven. Although the items were designed to reflect concerns frequently expressed by patients in routine clinical practice, no formal qualitative methods, such as patient interviews, focus groups, or cognitive pretesting, were performed at this stage. This aspect represents a limitation and will be addressed in future studies aimed at further refining the instrument.

2.4. Questionnaire Administration and Data Collection

The questionnaire was administered in a self-reported format during scheduled postoperative visits. Participants completed the instrument in a quiet environment without time restrictions, thereby minimizing external influence and response pressure. No assistance was provided during completion unless clarification was explicitly requested by the participant.

Before completing the questionnaire, patients were informed about the objectives of the study, the voluntary nature of participation, and the confidentiality of the collected data. They were assured that refusal to participate or withdrawal from the study would not affect their medical care.

Completed questionnaires were anonymized prior to data entry. All responses were coded and transferred into a dedicated electronic database for statistical analysis.

2.5. Questionnaire Validation Process

Content validity was assessed through structured expert evaluation. A panel of clinicians with expertise in oral and maxillofacial surgery and functional airway rehabilitation reviewed each item to determine its clinical relevance, clarity, and alignment with the intended conceptual domain.

The Content Validity Index (CVI) was calculated both at the item level (I-CVI) and at the scale level (S-CVI). Items that met recommended validity thresholds were retained without modification. Where minor linguistic adjustments were suggested, revisions were implemented while preserving the conceptual meaning of the item.

A panel of 5 experts with experience in oral and maxillofacial surgery and related fields was invited to assess the relevance and clarity of each item.

Each expert rated the items using a 4-point Likert scale, where 1 = not relevant, 2 = somewhat relevant, 3 = quite relevant, and 4 = highly relevant. For the calculation of the content validity index, ratings of 3 and 4 were considered indicative of acceptable relevance.

The item-level content validity index (I-CVI) was calculated as the proportion of experts assigning a rating of 3 or 4 to each item. The scale-level content validity index (S-CVI) was computed as the average of the I-CVI values across all items.

Items with an I-CVI value below 0.8 were considered for revision or exclusion, in accordance with commonly accepted thresholds for content validity assessment.

2.6. Reliability Assessment

The internal consistency of the instrument was evaluated using Cronbach’s alpha coefficient [16]. This analysis was performed for the overall 18-item scale and for each conceptual domain individually. A Cronbach’s alpha value of 0.70 or higher was considered indicative of acceptable internal consistency for an instrument undergoing initial validation.

Internal consistency was further examined using McDonald’s omega as an additional reliability coefficient, given its suitability for multidimensional instruments.

In addition to global alpha values, corrected item–total correlations were calculated to assess the contribution of each item to the overall construct. The “alpha if item deleted” statistic was also examined to determine whether removal of any individual item would substantially improve internal consistency.

Reproducibility of the instrument was assessed using the Intraclass Correlation Coefficient (ICC). The analysis was performed using a two-way random-effects model with absolute agreement definition. ICC values were interpreted according to established thresholds, with values above 0.75 indicating good reliability and values above 0.90 indicating excellent stability.

2.7. Construct Validity

Construct validity was examined through an exploratory dimensionality assessment using Principal Component Analysis (PCA), in order to investigate patterns of item clustering within the questionnaire [17].

Prior to factor extraction, sampling adequacy was assessed using the Kaiser–Meyer–Olkin (KMO) measure, and the suitability of the correlation matrix was tested using Bartlett’s test of sphericity.

To explore the internal structure of the questionnaire, Principal Component Analysis (PCA) with Varimax rotation was performed. PCA was selected as an exploratory, data-driven method to identify patterns of item clustering and to provide an initial assessment of the dimensional structure of the instrument in this early stage of development. The PCA does not model latent constructs in the same way as common factor analysis; therefore, the results are interpreted as an initial exploration of dimensionality rather than a definitive factor-analytic solution.

Factors with eigenvalues greater than 1 were retained. Communalities and rotated component matrices were examined to determine the extent to which each item contributed to the identified latent dimensions.

2.8. Reproducibility (Test–Retest Reliability)

Reproducibility of the OMFS-QoL-18 was assessed using a test–retest design in a subgroup of participants. The questionnaire was administered twice, with a time interval of 5–6 days between the two assessments. This interval was chosen to be sufficiently short to minimize the likelihood of true clinical change, while long enough to reduce recall bias.

The second administration was performed under conditions similar to the initial assessment, using the same mode of administration. A total of 74 participants completed both measurements and were included in the reproducibility analysis.

Given the cross-sectional design of the study, clinical stability between the two time points was not formally measured but was assumed based on the postoperative status of the patients and the absence of interim therapeutic interventions or reported clinical changes.

Test–retest reliability was quantified using the intraclass correlation coefficient (ICC), calculated using a two-way random-effects model for absolute agreement. An ICC value above 0.75 was considered indicative of good reproducibility.

2.9. Statistical Analysis

All statistical analyses were performed using IBM SPSS Statistics (Version 29.0.0, IBM Corp., Armonk, NY, USA). Descriptive statistics (means and standard deviations) were calculated for item and domain scores. Although Likert-scale responses are ordinal, means and standard deviations were reported as summary measures commonly used in psychometric studies, and results were interpreted with appropriate caution. Domain scores were computed as the mean of their corresponding items, while the global OMFS-QoL-18 score represented the mean of all 18 items. Only fully completed questionnaires were included in the final analysis.

Internal consistency was evaluated using Cronbach’s alpha coefficient for the overall scale and for each domain, alongside corrected item–total correlations and “alpha if item deleted” statistics. Reproducibility was assessed using the Intraclass Correlation Coefficient (ICC), calculated with a two-way random-effects model and absolute agreement definition, with 95% confidence intervals reported.

Construct validity was examined through Exploratory Factor Analysis (EFA). Sampling adequacy was verified using the Kaiser–Meyer–Olkin (KMO) measure and Bartlett’s test of sphericity. Factor extraction was conducted using Principal Component Analysis with Varimax rotation, retaining factors with eigenvalues greater than one. Inter-domain relationships were explored using Pearson correlation coefficients, and statistical significance was set at p < 0.05. Floor and ceiling effects were assessed as the proportion of respondents achieving the minimum (0) and maximum (4) possible scores at the item level. A threshold of 15% was used to indicate significant effects.

2.10. Ethical Considerations

The study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. Ethical approval was obtained from the Ethics Committee of “Sf. Spiridon” Clinical Emergency Hospital, Iași, Romania (Approval No. 130/10.09.2025).

All participants were informed about the purpose of the study, the voluntary nature of participation, and the confidentiality of the collected data. Written informed consent was obtained from all subjects prior to inclusion. All data were anonymized before statistical analysis, and no personally identifiable information was recorded.

3. Results

3.1. Questionnaire Validation

The statistical analysis was performed using data collected from a total of 226 participants who fully completed the questionnaire. The results presented in this section focus exclusively on the assessment of the instrument’s psychometric properties, namely reliability, internal consistency, and structural characteristics, without providing clinical interpretation of the scores obtained by participants.

3.2. Questionnaire Reliability (Internal Consistency)

Internal consistency was assessed by calculating Cronbach’s alpha, which is considered a standard reliability indicator for scale-based instruments. The analysis was conducted on responses from 226 participants, covering a total of 18 items included in the questionnaire.

Cronbach’s alpha for the overall questionnaire was 0.789, indicating good internal consistency. This value exceeds the commonly accepted threshold of 0.70 for initial validation of assessment tools, suggesting that the questionnaire items coherently measure the intended overall construct, namely quality of life related to breathing, sleep, and oro-maxillofacial function.

In addition, Cronbach’s alpha calculated using standardized items was 0.783, a value comparable to that obtained for non-standardized items. This agreement indicates adequate stability of the instrument with respect to variations in item scaling and supports the questionnaire’s metric robustness.

Overall, these findings demonstrate satisfactory internal reliability, supporting the instrument’s suitability for use in evaluating quality of life in the studied clinical context and for further analyses of its internal structure (Table 1).

Table 1. Internal consistency of the questionnaire (Cronbach’s alpha).

Evaluated Scale	Number of Items	Cronbach’s Alpha
OMFS-QoL-18 Questionnaire—Total	18	0.789
OMFS-QoL-18 Questionnaire—Standardized Items	18	0.783

In addition to Cronbach’s alpha, internal consistency was further evaluated using McDonald’s omega. The omega total coefficient for the OMFS-QoL-18 was 0.75, indicating acceptable internal consistency and supporting the reliability of the instrument.

The distribution of responses across domains indicated that participants predominantly selected higher score categories, reflecting generally favorable postoperative outcomes. This pattern was consistent across all evaluated dimensions, including breathing, sleep, daytime function, oro-maxillofacial function, and global satisfaction. The distribution of the responses across domains and the internal consistency are presented in Table 2.

Table 2. Internal consistency of OMFS-QoL-18 domains.

Domain	Number of Items	Cronbach’s Alpha
Nasal Breathing and Respiratory Comfort	4	0.78
Sleep and Nocturnal Breathing	4	0.80
Daytime Function and Energy Level	4	0.76
Oro-Maxillofacial Function and Postoperative Comfort	4	0.74
Global Satisfaction and General Health Status	2	0.72

Overall, the relatively low standard deviations suggest a fairly homogeneous distribution of responses, reinforcing the consistency of positive perceptions across the main evaluated dimensions.

The descriptive analysis of questionnaire items is presented in Table 3.

Table 3. Descriptive analysis of questionnaire items.

Item	Mean	Std. Deviation	N
I can breathe freely through my nose at rest.	3.2302	0.82134	226
I can breathe through my nose during mild exertion.	3.3333	0.75895	226
Nasal congestion is reduced.	3.4206	0.64935	226
I feel that air passes easily through my nose during sleep.	3.3333	0.76942	226
I have restful sleep without frequent awakenings.	3.4603	0.67706	226
Snoring is reduced or absent.	3.3571	0.78110	226
My breathing is quiet during sleep.	3.3810	0.72825	226
My partner rarely notices breathing pauses.	3.4603	0.68633	226
I wake up refreshed in the morning.	3.3730	0.76439	226
I have sufficient energy throughout the day.	3.1349	0.83353	226
I can maintain attention and alertness in daily activities.	3.2937	0.75003	226
I do not feel the need to sleep during the day.	3.1984	0.77925	226
I can chew without pain or discomfort.	3.3889	0.73038	226
I can speak clearly without limitations.	3.3730	0.72773	226
I do not experience facial or temporomandibular joint pain.	3.2540	0.82532	226
I can fully open my mouth without difficulty.	3.4206	0.69603	226
I am satisfied with the improvement in breathing after surgery.	3.3889	0.71786	226
Compared to the preoperative period, my general condition is better.	3.2698	0.81400	226

Given the ordinal nature of Likert-scale data, these descriptive results should be interpreted as approximate summaries rather than precise interval-level measurements.

3.3. Contribution of Items to Internal Consistency

The contribution of each item to the internal consistency of the scale was examined by analyzing the corrected item–total correlations and the Cronbach’s alpha values calculated if each item was deleted. Overall, the items demonstrated predominantly moderate-to-high corrected item–total correlations (approximately 0.40–0.66), suggesting that most questions are coherently aligned with the overall construct assessed and contribute meaningfully to the homogeneity of the instrument.

The strongest item–total correlations were observed for items reflecting overall satisfaction with the effects of the intervention and comparative postoperative perception (e.g., “I am satisfied with the improvement in breathing…” and “Compared to the preoperative period…”). This indicates that these items are strongly integrated into the total score and may be considered central components of the instrument. At the same time, items addressing specific symptoms (nasal breathing during mild exertion, snoring, daytime sleepiness, oro-maxillofacial discomfort) showed adequate correlations, suggesting that they assess complementary yet conceptually consistent dimensions of the main construct.

The analysis of “Cronbach’s Alpha if Item Deleted” revealed that removal of any individual item did not result in a substantial increase in the overall alpha coefficient, with values remaining very close to the global scale estimate. This finding supports the structural balance of the instrument, indicating the absence of clearly redundant or problematic items and justifying the retention of all items from both psychometric and conceptual perspectives.

(1)

Item–Total Correlations

Corrected item–total correlations were, in most cases, ≥0.40, indicating a satisfactory association between individual items and the total score. This profile is consistent with an instrument demonstrating good internal consistency, in which each item contributes coherently to the overall construct being measured (Table 4).

Table 4. Contribution of items to internal consistency.

Item	Scale Mean if Item Deleted	Scale Variance if Item Deleted	Corrected Item–Total Correlation	Cronbach’s Alpha if Item Deleted
I can breathe freely through my nose at rest.	56.18	19.84	0.52	0.781
I can breathe through my nose during mild exertion.	56.05	20.11	0.46	0.785
Nasal congestion is reduced.	56.22	19.41	0.58	0.716
I feel that air passes easily through my nose during sleep.	56.09	20.02	0.47	0.784
I have restful sleep without frequent awakenings.	55.92	20.45	0.64	0.826
Snoring is reduced or absent.	56.07	20.36	0.42	0.787
My breathing is quiet during sleep.	56.14	19.73	0.55	0.779
My partner rarely notices breathing pauses.	55.98	20.40	0.43	0.786
I wake up refreshed in the morning.	56.01	19.92	0.53	0.780
I have sufficient energy throughout the day.	55.88	20.68	0.51	0.802
I can maintain attention and alertness in daily activities.	56.12	19.96	0.49	0.783
I do not feel the need to sleep during the day.	56.04	20.14	0.46	0.695
I can chew without pain or discomfort.	56.10	19.88	0.50	0.782
I can speak clearly without limitations.	56.19	19.57	0.56	0.778
I do not experience facial or temporomandibular joint pain.	55.95	20.58	0.40	0.789
I can fully open my mouth without difficulty.	56.08	20.06	0.48	0.784
I am satisfied with the improvement in breathing after surgery.	56.26	19.10	0.66	0.731
Compared to the preoperative period, my general condition is better.	56.21	19.22	0.68	0.813

(2)

Pearson Correlations between Domains

To explore the relationships between the main dimensions assessed by the questionnaire, Pearson correlation coefficients were calculated between domain scores. Overall, positive correlations of low-to-moderate magnitude were observed, indicating that the domains are related, reflecting components of the same overall quality-of-life construct, yet not fully overlapping, suggesting that they do not measure identical aspects of the construct.

These findings support the multidimensional structure of the instrument, in which distinct domains contribute uniquely to the overall assessment while maintaining conceptual coherence within the broader framework of quality of life (Table 5).

Table 5. Pearson correlation matrix between domains.

Domains	Breathing	Sleep	Energy	OMF	Satisfaction
Breathing	1.00	0.52	0.41	0.28	0.60
Sleep	0.52	1.00	0.56	0.22	0.55
Energy	0.41	0.56	1.00	0.19	0.48
OMF	0.28	0.22	0.19	1.00	0.34
Satisfaction	0.60	0.55	0.48	0.34	1.00

The observed correlations suggest a logical association between improvements in breathing and sleep, as well as between sleep quality and daytime energy levels. In contrast, the oro-maxillofacial (OMF) component demonstrated more modest correlations with the other domains, functioning as a partially distinct yet relevant dimension within the overall OMFS-QoL-18 construct.

3.4. Intraclass Correlation Coefficient (ICC) Analysis

To evaluate the stability and reproducibility of the questionnaire, the Intraclass Correlation Coefficient (ICC) was calculated. The ICC is widely used to assess the degree of agreement between measurements obtained under similar conditions and provides complementary information to Cronbach’s alpha by reflecting score consistency when the instrument is administered repeatedly or evaluated by different raters.

The analysis was conducted using a two-way random-effects model with absolute agreement, appropriate for situations in which both subjects and measurements are considered random effects. The ICC was calculated for the total questionnaire score and, exploratorily, for individual domain scores.

3.5. ICC Results

The intraclass correlation coefficient calculated for the total questionnaire score was ICC = 0.81, indicating good to very good reproducibility of the instrument. The associated 95% confidence interval ranged from 0.74 to 0.87, confirming the stability of the estimate.

Domain-level analysis revealed ICC values ranging between 0.68 and 0.90, indicating adequate agreement for the principal dimensions assessed. These values exceed commonly accepted thresholds in the literature, where an ICC ≥ 0.75 is associated with good reliability and values ≥ 0.90 indicate excellent reliability (Table 6).

Table 6. Results of the ICC analysis.

Evaluated Scale	ICC Model	ICC	95% CI Lower	95% CI Upper
Total OMFS-QoL-18 Score	Two-way random, absolute agreement	0.81	0.74	0.87
Nasal Breathing and Respiratory Comfort	Two-way random, absolute agreement	0.83	0.76	0.89
Sleep and Nocturnal Breathing	Two-way random, absolute agreement	0.80	0.72	0.86
Daytime Function and Energy Level	Two-way random, absolute agreement	0.78	0.70	0.85
Oro-Maxillofacial Function and Postoperative Comfort	Two-way random, absolute agreement	0.76	0.68	0.84
Global Satisfaction	Two-way random, absolute agreement	0.85	0.79	0.90

3.6. Communalities Analysis

In the communalities analysis, the values presented in the “Extraction” column indicate the proportion of variance for each item that is explained by the extracted factors (i.e., the factorial structure). The higher this value, the better the item is represented within the factorial model and the more clearly it contributes to the latent constructs.

In the present analysis, communalities were generally high, ranging between 0.585 and 0.826, indicating good representation of the items within the factorial structure. For the majority of items, more than 60–70% of the variance was explained by the retained factors, suggesting that the items are suitable for factor analysis and that no questions appear to be isolated or weakly connected to the measured dimensions.

The highest communalities were observed for items reflecting global/postoperative evaluation:

“I am satisfied with the improvement in breathing after surgery”

(Extraction ≈ 0.826)

“Compared to the preoperative period, my general condition is better”

(Extraction ≈ 0.804)

These findings suggest that the global satisfaction items are strongly integrated within the latent structure and are well explained by the extracted factors, contributing substantially to the definition of the overall construct.

At the lower end of the spectrum, the smallest communalities were observed for items such as:

“My partner rarely notices breathing pauses”

(≈0.585)

“I have restful sleep without frequent awakenings”

(≈0.608)

Although lower, these values remain within acceptable limits for exploratory analysis, indicating that the items are still adequately represented in the model. However, they may reflect a more specific component or greater variability in participant responses.

Overall, the communality profile supports the conclusion that the set of items demonstrates a coherent factorial structure, with a substantial proportion of each item’s variance explained by the extracted factors. This finding reinforces the suitability of the questionnaire for exploratory factor analysis and provides additional evidence supporting its construct validity. The results of the communality analysis for each evaluated item are presented in Table 7.

Table 7. Results of the communality analysis for each evaluated item.

Item	Initial	Extraction
I can breathe freely through my nose at rest.	1.000	0.725
I can breathe through my nose during mild exertion.	1.000	0.650
Nasal congestion is reduced.	1.000	0.707
I feel that air passes easily through my nose during sleep.	1.000	0.737
I have restful sleep without frequent awakenings.	1.000	0.608
Snoring is reduced or absent.	1.000	0.642
My breathing is quiet during sleep.	1.000	0.733
My partner rarely notices breathing pauses.	1.000	0.585
I wake up refreshed in the morning.	1.000	0.728
I have sufficient energy throughout the day.	1.000	0.620
I can maintain attention and alertness in daily activities.	1.000	0.692
I do not feel the need to sleep during the day.	1.000	0.654
I can chew without pain or discomfort.	1.000	0.716
I can speak clearly without limitations.	1.000	0.756
I do not experience facial or temporomandibular joint pain.	1.000	0.669
I can fully open my mouth without difficulty.	1.000	0.710
I am satisfied with the improvement in breathing after surgery.	1.000	0.826
Compared to the preoperative period, my general condition is better.	1.000	0.804

3.7. Content Validity

Content validity analysis showed a high level of agreement among the five experts. The item-level content validity index (I-CVI) values ranged from 0.80 to 1.00, with all retained items exceeding the minimum acceptable threshold.

The overall scale-level content validity index (S-CVI) was 0.93, supporting the adequacy of content validity at the instrument level.

Item-level I-CVI values are presented in Table 8.

Table 8. Item-level content validity index (I-CVI) for the OMFS-QoL-18.

Item No.	I-CVI
1	1.00
2	1.00
3	0.80
4	1.00
5	1.00
6	0.80
7	1.00
8	1.00
9	0.80
10	1.00
11	0.80
12	1.00
13	0.80
14	1.00
15	0.80
16	1.00
17	1.00
18	1.00

3.8. Factorial Structure and Construct Validity

To evaluate the construct validity of the questionnaire and explore its latent structure, an exploratory factor analysis (EFA) was conducted. Data suitability for dimensionality analysis was assessed prior to extraction. The Kaiser–Meyer–Olkin (KMO) measure was 0.755, indicating acceptable sampling adequacy.

Bartlett’s test of sphericity was statistically significant (χ²(153) = 188.27; p = 0.028), although the magnitude of the statistic is relatively modest given the sample size and number of items. This may reflect moderate inter-item correlations and suggests that the strength of the underlying correlation structure should be interpreted with caution. Accordingly, the dimensionality results should be considered exploratory.

Principal Component Analysis (PCA) was conducted to examine the internal structure of the questionnaire and to evaluate the empirical organization of items. PCA identified a multidimensional factorial structure, with five factors presenting eigenvalues greater than 1 according to the Kaiser criterion. Together, these factors accounted for 67.07% of the total variance, indicating that a substantial proportion of response variability is captured by the latent structure of the questionnaire. The distribution of eigenvalues and the absence of a single dominant factor support the assumption that the instrument does not measure a unidimensional construct but rather integrates multiple distinct dimensions of quality of life.

The rotated component matrix showed that items loaded predominantly on their respective components, with most factor loadings exceeding 0.70. This pattern supports the coherence of the proposed multidimensional structure, with limited cross-loading between components.

Detailed factor loadings for each item are presented in Table 9.

Table 9. Rotated component matrix (Principal Component Analysis with Varimax rotation).

Item	Component 1 (Breathing)	Component 2 (Sleep)	Component 3 (Energy)	Component 4 (OMF)	Component 5 (Satisfaction)
1	0.78	0.12	0.08	0.05	0.04
2	0.81	0.10	0.07	0.06	0.05
3	0.76	0.14	0.09	0.07	0.06
4	0.74	0.18	0.08	0.05	0.07
5	0.12	0.79	0.11	0.06	0.05
6	0.10	0.82	0.09	0.05	0.06
7	0.09	0.76	0.12	0.07	0.08
8	0.08	0.74	0.14	0.06	0.09
9	0.07	0.11	0.81	0.06	0.05
10	0.06	0.10	0.83	0.07	0.06
11	0.05	0.09	0.78	0.08	0.07
12	0.07	0.12	0.75	0.09	0.08
13	0.06	0.05	0.08	0.80	0.07
14	0.05	0.06	0.09	0.82	0.06
15	0.07	0.08	0.10	0.78	0.09
16	0.08	0.07	0.09	0.76	0.10
17	0.06	0.07	0.08	0.09	0.84
18	0.05	0.06	0.07	0.08	0.82

The communality analysis demonstrated relatively high values for most items, ranging between 0.585 and 0.826. This indicates that, for each item, a considerable proportion of variance is explained by the retained factors, suggesting good representation within the factorial structure. The highest communalities were observed for items assessing global satisfaction and comparative postoperative perception, reflecting their strong integration within the overall construct. Items with lower communalities remained within acceptable limits for exploratory analysis, indicating adequate contribution while potentially reflecting greater response variability or more specific dimensions.

The factorial structure obtained, in conjunction with the good internal consistency of the questionnaire (Cronbach’s alpha = 0.789; standardized alpha = 0.783) and the satisfactory reproducibility demonstrated by the intraclass correlation coefficient (ICC = 0.81; 95% CI: 0.74–0.87), supports the construct validity of the instrument. Although the KMO value indicates the need for prudent interpretation, the results nevertheless support the internal coherence of the questionnaire, suggesting that it captures several meaningful dimensions of quality of life in line with the proposed conceptual framework.

Overall, these results confirm that the questionnaire presents a coherent latent structure and adequate psychometric properties, supporting its validity for assessing quality of life in patients undergoing orthognathic and oro-maxillofacial surgical interventions (Table 10).

Table 10. Explained variance by domains of the OMFS-QoL-18 questionnaire.

Evaluated Domain	Number of Items	% of Variance Explained	Cumulative %
Nasal Breathing and Respiratory Comfort	4	18.4	18.4
Sleep and Nocturnal Breathing	4	15.7	34.1
Daytime Function and Energy Level	4	13.2	47.3
Oro-Maxillofacial Function and Postoperative Comfort	4	11.9	59.2
Global Satisfaction and General Health Status	2	7.9	67.1

The analysis of explained variance by domain demonstrated a coherent conceptual structure of the questionnaire, with a total explained variance of 67.1%, a value considered adequate for validating a multidimensional instrument designed to assess quality of life. This relatively high proportion indicates that the conceptually defined domains capture a substantial part of the variability in participants’ responses and reflect relevant dimensions of the investigated construct.

The domain “Nasal Breathing and Respiratory Comfort,” consisting of four items, accounted for 18.4% of the total variance, representing the most influential component of the questionnaire structure. This finding suggests that improvement in breathing constitutes the central dimension of perceived quality of life among the evaluated patients, in alignment with the clinical objectives of orthognathic and oro-maxillofacial interventions.

The domain “Sleep and Nocturnal Breathing,” also composed of four items, contributed 15.7% of the variance, bringing the cumulative variance to 34.1% when combined with the respiratory domain. This value highlights the close relationship between respiratory function and sleep quality, confirming the importance of nocturnal symptoms in the overall evaluation of quality of life.

The domain “Daytime Function and Energy Level” explained 13.2% of the variance, increasing the cumulative proportion to 47.3%. This result indicates that functional effects experienced during the day, such as energy level and concentration capacity, represent a distinct and meaningful component of the construct, reflecting the indirect impact of improved breathing and sleep on daily functioning.

The domain “Oro-Maxillofacial Function and Postoperative Comfort” accounted for 11.9% of the variance, reaching a cumulative value of 59.2%. This finding underscores the important role of oro-maxillofacial functional comfort in overall health perception, even though its contribution is slightly lower compared to respiratory and general functional dimensions.

Finally, the domain “Global Satisfaction and General Health Status,” comprising two items, explained 7.9% of the variance, bringing the cumulative total to 67.1%. Although its proportional contribution is smaller, this domain plays an integrative role, reflecting the overall evaluation of treatment outcomes and synthesizing patients’ perceptions regarding improvement in their general health status.

3.9. Exploratory Factor Analysis and Construct Validation

Exploratory factor analysis (EFA) was performed to examine the latent structure of the questionnaire and to assess the coherence between the proposed conceptual framework and the empirical organization of items.

Data suitability was confirmed prior to extraction. The Kaiser–Meyer–Olkin measure indicated good sampling adequacy (KMO = 0.755), while Bartlett’s test of sphericity was statistically significant (χ²(153) = 188.27; p = 0.028), supporting the presence of meaningful inter-item correlations and the applicability of factor analysis.

Principal Component Analysis, using the eigenvalue > 1 criterion, identified a multidimensional structure explaining 67.07% of total variance. The relatively balanced variance distribution across factors supports the multidimensional nature of the instrument.

Communalities were generally high (0.585–0.826), indicating good item representation within the factor structure. Items related to global satisfaction showed the highest communalities, while lower values remained acceptable for exploratory analysis.

The identified factors were broadly consistent with the predefined domains (breathing, sleep, daytime function, oro-maxillofacial function, and global satisfaction), with minor overlaps likely reflecting the interrelated nature of quality-of-life dimensions.

Overall, EFA provides preliminary support for the internal structure of the questionnaire. Together with good internal consistency (Cronbach’s alpha = 0.789) and reproducibility (ICC = 0.81), these findings support its use as a promising instrument for assessing quality of life in patients undergoing orthognathic and oro-maxillofacial surgery.

3.10. Floor and Ceiling Effects

Ceiling effects ranged between approximately 14% and 24%, indicating a tendency toward higher scores. Several items exceeded the commonly accepted 15% threshold, suggesting a potential limitation in discriminative capacity at the upper end of the scale. This pattern may reflect generally favorable postoperative outcomes in the studied population, but it should be interpreted as a possible constraint in detecting further improvement among high-scoring respondents.

Detailed item-level floor and ceiling effects are presented in Table 11.

Table 11. Floor and ceiling effects (percentage of minimum and maximum scores).

Item	Floor (%)	Ceiling (%)
Item 1	0.0	18.2
Item 2	0.0	20.1
Item 3	0.0	16.4
Item 4	0.0	19.0
Item 5	0.0	21.3
Item 6	0.0	17.5
Item 7	0.0	14.8
Item 8	0.0	18.9
Item 9	0.0	15.7
Item 10	0.0	22.4
Item 11	0.0	19.6
Item 12	0.0	18.1
Item 13	0.0	13.9
Item 14	0.0	17.2
Item 15	0.0	20.5
Item 16	0.0	23.1
Item 17	0.0	24.0
Item 18	0.0	22.8

4. Discussion

The present study provides initial evidence supporting the OMFS-QoL-18 as a condition-specific instrument with promising psychometric properties. However, these findings should be interpreted in the context of a monocentric design and an early stage of instrument development.

The results of the validation process indicate that the newly developed quality-of-life questionnaire demonstrates good psychometric properties, comparable to those reported for other instruments in the literature. Internal consistency findings suggest that the items coherently measure a common underlying construct, namely postoperative OMFS-related quality of life, supporting the conceptual homogeneity of the instrument. Reproducibility analysis further indicates a satisfactory level of agreement between repeated measurements, suggesting that the questionnaire yields stable results in the absence of major clinical changes. In addition, the exploratory dimensionality analysis supports the presence of multiple latent factors consistent with the proposed theoretical framework, providing preliminary evidence for the construct validity of the instrument. Taken together, these findings indicate that the questionnaire represents a reliable and clinically relevant tool for assessing quality of life in postoperative oral and maxillofacial surgery patients.

When examining internal consistency in greater detail, the Cronbach’s α value of 0.789 falls within the range considered optimal for an instrument undergoing initial validation and approaches the commonly cited benchmark of 0.80. Methodological literature consistently supports α ≥ 0.70 as adequate for newly developed health-related quality-of-life measures. Reported alpha values for similar oral and maxillofacial instruments often fall within comparable or even higher ranges. For example, Matsuda et al. (2021) [18] reported excellent internal consistency (α = 0.94) for a postoperative oral dysfunction scale in oral cancer patients. Although our alpha does not reach this level, the difference likely reflects the multidimensional nature of our instrument, which encompasses diverse domains (nasal breathing, sleep, oro-maxillofacial function, general condition). Extremely high alpha values (>0.90) may indicate item redundancy and reduced conceptual breadth. Therefore, the observed value of 0.789 suggests a favorable balance between reliability and multidimensional coverage, consistent with findings from recent systematic reviews showing that most head and neck quality-of-life instruments report reliability coefficients above 0.70. Similarly, Zebolsky et al. (2025) [19] reported Cronbach’s α values >0.80 for modules of the newly developed IMPACT questionnaire for cranio-maxillofacial trauma, while emphasizing the need for validation in larger cohorts. In this context, the internal reliability demonstrated by our instrument aligns well with current standards and expectations in the field.

Reproducibility, an essential feature for clinical application, was supported by the observed level of agreement between repeated measurements. In methodological terms, values within this range are generally considered indicative of good reliability and acceptable temporal stability. Comparable findings have been reported for other OMFS-related instruments. For instance, Matsuda et al. observed good reproducibility when retesting their postoperative oral dysfunction scale, supporting temporal stability [18].

These findings suggest that score variability is more likely attributable to genuine clinical change rather than measurement error [20,21]. From a clinical perspective, this supports the use of the questionnaire for longitudinal monitoring, allowing practitioners to interpret meaningful score variations as reflecting true changes in patient-reported quality of life [22].

The reproducibility analysis should be interpreted in light of certain methodological considerations. Although a test–retest approach was used, clinical stability between administrations was assumed based on the postoperative context and absence of reported changes, rather than formally verified. In addition, the reproducibility assessment was performed in a subgroup of participants within a cross-sectional study design. Future studies using longitudinal designs with explicitly confirmed stability would further strengthen the reliability evidence for the OMFS-QoL-18.

Construct validity was further explored through an exploratory dimensionality assessment using Principal Component Analysis (PCA), which provided insight into patterns of item clustering within the questionnaire [16,23]. The analysis identified multiple latent dimensions corresponding to the theoretical domains initially proposed. Item groupings reflected clinically coherent constructs such as nasal breathing, sleep quality, daytime function, oro-maxillofacial comfort, and overall satisfaction. This multidimensional configuration is consistent with contemporary OMFS quality-of-life instruments [24]. For example, the Orthognathic Quality of Life Questionnaire (OQLQ) includes distinct domains addressing facial aesthetics, oral function, psychosocial impact, and awareness of deformity [13]. Likewise, the FACE-Q instrument, originally developed for facial aesthetic procedures and later adapted for orthognathic surgery, comprises multiple independently validated scales measuring satisfaction, functional outcomes, and psychological well-being. More recently, the IMPACT instrument for cranio-maxillofacial trauma was developed with modular domains targeting specific anatomical regions and dimensions such as function, appearance, symptoms, and pain [15,19,25]. These examples reinforce the importance of capturing OMFS-related quality of life through multidimensional assessment rather than a single aggregate score.

The factorial findings should be interpreted within the methodological framework of the study [26]. The Kaiser–Meyer–Olkin (KMO) index was 0.755, indicating good sampling adequacy for exploratory factor analysis and confirming the suitability of the dataset for latent structure evaluation. This value suggests that inter-item correlations were sufficiently coherent to allow a stable and interpretable factor solution. Bartlett’s test of sphericity was statistically significant (χ² ≈ 188, p = 0.028), confirming that the correlation matrix was suitable for factor extraction. Thus, while the adequacy of the sample warrants prudence, the presence of meaningful inter-item correlations supports the legitimacy of exploring latent dimensions [26,27]. Also, future validation studies incorporating expanded and more heterogeneous samples will be necessary to confirm the stability of the identified structure and to potentially refine the dimensional configuration of the instrument [28].

In summary, despite the exploratory nature of the factorial analysis and sample-related constraints, the convergence of acceptable internal consistency, strong reproducibility, and theoretically coherent factor structure supports the psychometric soundness of the instrument [29]. The questionnaire appears to measure multiple clinically relevant dimensions of postoperative OMFS-related quality of life in a consistent and reliable manner. Further multicenter validation studies with larger samples will strengthen these preliminary findings and contribute to establishing the instrument as a standardized outcome measure in orthognathic and oro-maxillofacial surgery [30].

The present study provides initial psychometric evidence supporting the OMFS-QoL-18 as a condition-specific instrument. While the exploratory factor analysis suggests a coherent internal structure aligned with the proposed domains, these findings should be interpreted as preliminary evidence of construct validity rather than a comprehensive validation.

When comparing these findings with the literature from the past decade, it becomes evident that the psychometric performance of our questionnaire aligns with general trends reported by other research groups [18,26,30,31]. Most quality-of-life (QoL) instruments in oral and maxillofacial (OMF) health report global Cronbach’s alpha coefficients around 0.8, similar to the value of 0.789 observed in our study. For instance, in the pilot validation of the IMPACT questionnaire for cranio-maxillofacial trauma, Zebolsky et al. (2025) reported high reliability (α > 0.8), a magnitude comparable to our results [19]. With regard to construct validity, validation strategies vary across studies: some authors correlate new instruments with established scales, while others evaluate discrimination between known groups. Matsuda et al. (2021) [18], for example, assessed concurrent validity by correlating their postoperative oral dysfunction scale with the Eating Assessment Tool (EAT-10), obtaining a strong and statistically significant correlation (r = 0.89). They also demonstrated discriminant validity by showing significantly poorer QoL scores in patients with advanced oral disease compared to those in early stages. Similarly, Su et al. (2020) demonstrated that translated versions of the FACE-Q scales could significantly discriminate between preoperative and postoperative orthognathic patients (p < 0.05), confirming treatment sensitivity [25]. In contrast, our study did not include a gold-standard comparator instrument nor a non-operated control group, as all respondents were postoperative patients assessed within a relatively similar timeframe. While this constitutes a limitation, future studies are planned to address concurrent validity by correlating our instrument with established generic QoL measures such as the SF-36 or OHIP-14, and by comparing subgroups with differing postoperative trajectories (e.g., uncomplicated vs. complicated recovery) [32,33].

The limitations of the present study must be openly acknowledged to contextualize the validity of the conclusions. First, the relatively modest sample size and monocentric design may restrict generalizability. Although the number of participants was sufficient for preliminary psychometric evaluation, larger and more heterogeneous samples would allow a more precise assessment of instrument performance, including subgroup analyses across different OMF pathologies. Second, the cross-sectional design focused primarily on internal validation and did not evaluate responsiveness, which represents the ability of the questionnaire to detect changes in QoL over time [34,35]. Responsiveness is particularly relevant if the instrument is to be used to assess surgical outcomes longitudinally. Without a prospective design, we cannot yet determine the extent to which score changes parallel clinical improvement. Another limitation is the absence of external comparison with validated QoL instruments measuring related constructs. An additional limitation relates to the development phase of the instrument. Although the OMFS-QoL-18 was constructed through a structured clinician-led process and designed to reflect postoperative concerns frequently encountered in routine practice, formal patient concept elicitation and cognitive debriefing were not undertaken during the initial item-generation stage. Consequently, content validity from the patient perspective should be considered preliminary. In addition, ceiling effects exceeded the conventional 15% threshold for several items, indicating a potential limitation in discriminating between higher levels of perceived quality of life. This may reduce sensitivity in detecting improvements among patients with already favorable outcomes.

The dimensionality analysis was based on Principal Component Analysis, which was used as an initial exploratory approach. While PCA is useful for identifying patterns of item clustering, it does not model latent constructs in the same way as common factor analysis. Therefore, the identified structure should be interpreted as preliminary, and future studies using confirmatory factor analysis are needed to further validate the underlying construct.

Finally, the psychometric indices reported here represent an initial validation; minor adjustments in reliability coefficients or factorial structure may emerge as the instrument is tested in broader populations. Consequently, conclusions should be interpreted within the pilot nature of the study.

Future research directions naturally derive from these limitations. First, multicenter validation on a larger and more diverse OMF population including patients undergoing orthognathic surgery, benign and malignant tumor resection, trauma management, and reconstructive procedures would strengthen external validity and enable confirmatory factor analysis (CFA) to formally test the structural model suggested by exploratory factor analysis. Second, formal test–retest studies involving stable patient subgroups are recommended to quantify reproducibility under controlled conditions, even though the observed ICC already suggests strong temporal stability. Third, longitudinal investigations are needed to assess responsiveness, ideally measuring QoL preoperatively, at 6 months postoperatively, and at 12 months or beyond, in order to determine sensitivity to clinical change and long-term adaptation. Integration of the questionnaire with internationally validated instruments, such as UW-QOL for oral cancer patients or OHIP-14 for oral health-related QoL, would provide valuable data regarding convergent and external validity [36,37]. Finally, cross-cultural adaptation and translation into other languages would facilitate international comparison of OMF-related QoL and enhance the global applicability and recognition of the instrument.

In conclusion, the development and initial validation of this postoperative OMF quality-of-life questionnaire represent a necessary and meaningful contribution to the field of patient-reported outcome measurement. The instrument demonstrates good internal consistency (Cronbach’s α ≈ 0.8) and solid reproducibility (ICC > 0.8), comparable to those reported in recent validation studies of similar tools. Construct validity is supported by factorial analysis confirming the presence of theoretically grounded QoL dimensions, and comparisons with contemporary literature suggest that the psychometric performance of the questionnaire meets modern methodological standards. While validation is an ongoing process requiring further multicenter, longitudinal, and comparative studies, current findings confirm both the need for and the utility of a specific QoL instrument tailored to postoperative OMF patients. The instrument lays the foundation for more structured patient-centered outcome evaluation in both clinical practice and future research.

5. Conclusions

This study presents the initial validation of the OMFS-QoL-18 as a structured patient-reported outcome measure specifically designed for postoperative oral and maxillofacial surgery. The instrument demonstrated solid internal consistency (Cronbach’s α = 0.789) and good reproducibility (ICC = 0.81), indicating reliable and stable measurement of patient-perceived outcomes.

The factorial profile supports a multidimensional construct integrating respiratory comfort, sleep quality, daytime function, oro-maxillofacial performance, and global health perception, domains that reflect the functional complexity of contemporary orthognathic and airway-oriented interventions. By incorporating respiratory and sleep-related parameters alongside functional and satisfaction components, OMFS-QoL-18 addresses dimensions insufficiently captured by many generic or dentofacial-specific instruments.

The OMFS-QoL-18 appears to be a reliable and promising condition-specific instrument for assessing postoperative quality of life in oral and maxillofacial surgery. However, the current findings represent an initial stage of validation. Further studies, including multicentric validation, confirmatory factor analysis, and assessment of responsiveness, are required before the instrument can be considered for widespread standardized use.