Decision Rules for Measurement Results in Testing and Medical Laboratories with ISO Accreditation Requirements

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper compares the requirements for testing (ISO 17025) to medical laboratories (ISO 15189) in terms of the reporting needs, in particular, the approach to MU. The article is novel and provocative. It is well-written. 

1. What is the aim of the author? It would help both the author and the reader if this were clearly stated.
2. Describe some examples of testing labs.
3. The concepts of safeguard bands and tolerance need to be more clearly defined. 
4. I don't believe Figures 3 and 4 add anything to the text and suggest they be deleted.
5. Line 43 - editorial - there are two full stops ..
6. Define the terms ASME and JCGM.
7. References should be provided to support the statements made in lines 122-129.
8.  SIPMeL M2-2 Recommendations - should be recommendations?
9. Line 230 - requires a reference to this statement.
10. Line 270 - 'personalised references' should be 'personalised reference intervals'.
11. Line 271, 272 - 'regarding' is used twice in the same sentence.
12. There is a discussion of RI and DLs, but no comment on their MU or CI. MU or CI should apply to the RI and DL as well as the measurement.
13. There is a move towards common reference intervals for a Region or a country to overcome some of the problems of cost and complexity. This is not mentioned.
14. Are there limitations in the paper?
15. Is reference 38 the correct reference for the text?

Author Response

General comment from the Author: The reviewers' comments accurately reflect the range of reactions—from enthusiastic approval to harsh criticism—that we would have expected from a group of laboratory specialists with diverse backgrounds and, consequently, very different perspectives. To us, they serve as evidence of the value of a contribution that compares objective realities from a perspective that is not uncritically tied to traditional practice. Answering all of the Reviewers' questions turned out to be very time-consuming and labor-intensive, almost like writing a new article.

• Comments1: What is the aim of the author?

Response 1: This article draws on insights gained from direct experience in laboratories and ISO accreditation processes within an accreditation body, comparing them with the content of the standards used in the accreditation of testing laboratories (ISO 17025) and medical laboratories (ISO 15189) to stimulate reflection on theoretical and, to some extent, speculative issues, from which scientifically sound practical guidance can be derived. ISO 17025 and ISO 15189 share the same origins but follow different paths and entail different practices in laboratories. A clarifying sentence has been added to the introduction and also in conclusions.

• Comments 2: Describe some examples of testing labs.

Response 2: See also RIMeL 15189 17025 DOI: 10.23736/S1825-859X.19.00033-1

The activities of testing laboratories consist of the analysis, diagnosis, and certification of compliance for materials, products, or processes. These activities are carried out for industrial, commercial, or forensic purposes using advanced instrumentation and standardized protocols. Laboratories can operate in a wide range of sectors, and their main activities include: Industrial and Mechanical Sector: Material strength testing, tensile testing, fatigue testing, and chemical or thermal analysis of components (e.g., for the automotive, aerospace, or railway sectors). Environmental Sector: Analysis of water, air, and soil samples (often conducted in Veneto by accredited bodies such as Arpa Veneto). Electrical and Electronic Sector: Electromagnetic compatibility and device safety testing. Testing in the following sectors: chemical; biological, microbiological; mechanical; electrical; serology, virology, cytology, parasitology; acoustics; physical mechanics (strength, fracture, textiles); physical ionizing radiation; civil engineering; ITT; biochemical; sensory; non-destructive testing; ecotoxicological; corrosion; metallographic.

After careful consideration of the Auditor’s request, it is not deemed useful to include this lengthy list in the article. Readers of articles such as this should already have sufficient information.

• Comments 3: The concepts of guard bands and tolerance need to be more clearly defined.

Response 3: A guard band, g to be calculated (see Figure 1) which defines an acceptance zone and a rejection zone. If the measurement result is within the acceptance zone the specifications are met and we can assess compliance. If the measurement result is in the rejection zone we can assess non compliance. https://www.eurachem.org/images/stories/leaflets/mu/compliance/eurachemcomplianceleaflet_EN.pdf. Guard-banding is one technique to protect against in-correct conformity decisions caused by measurement uncertainty or entity dispersion, where the region of permissible values of the entity’s quality characteristic is reduced in proportion to the actual measurement uncertainty or dispersion. https://metrology.wordpress.com/statistical-methods-index/basic-theory-of-measurement-and-error/conformity-assessment-introduction/guard-banding/. After careful consideration of the Auditor’s request, I believe that the concept is sufficiently described in Chapter 2 and in the source cited in Reference [7]. Although it is an important concept, elaborating on it further would take us too far afield from the article’s objectives, namely the analysis of differences between laboratories.

• Comments 4: I don't believe Figures 3 and 4 add anything to the text and suggest they be deleted.

Response 4: This request from the Reviewer is isolated. The concepts analyzed in this review pertain to practices that are deeply ingrained in laboratories and have been in use for a long time; as such, a critical reevaluation of them can be very difficult and may provoke fierce resistance. Figures 3 and 4 are not merely supplementary to the text; rather, they serve to reinforce the points made in the text and to stimulate the reader’s analogical thinking processes, alongside more deductive ones.

• Comments 5: Line 43 - editorial - there are two full stops ..

Response 5: Done, thanks

• Comments 6: Define the terms ASME and JCGM.

Response 6: American Society of Mechanical Engineers. (ASME); Joint Committee for Guides in Metrology (JCGM). In addition to appearing in the final list, the two abbreviations were explained in the text (line 60).

• Comments 7: References should be provided to support the statements made in lines 122-129.

Response 7: original lines 122-129 are on the number of subjects. The references [9-11] (CLSI EP28-A3c[9] + EP44) were added to the text.

• Comments 8: SIPMeL M2-2 Recommendations - should be recommendations?

Response 8: Line 152 and Ref. [15]. The uppercase is in the title of the document.

• Comments 9: Line 230 - requires a reference to this statement.

Response 9: “the “indirect” approach in the case in larger centralized laboratories”: This can be inferred from the definition provided, among other sources, by CLSI EP45: “analysis of typically large sets of sample data”. The text was integrated.

• Comments 10: Line 270 - 'personalised references' should be 'personalised reference intervals'.

Response 10: Done, thanks

• Comments 11: Line 271, 272 - 'regarding' is used twice in the same sentence.

Response 11: Two points are in the same sentence

• Comments 12: There is a discussion of RI and DLs, but no comment on their MU or CI. MU or CI should apply to the RI and DL as well as the measurement.

Response 12: That observation is correct; the issue is important. In fact, it is being discussed in EP44 5.3.3 Calculation of Confidence Intervals and 3.2 Number of Reference Individuals. However, after careful consideration, we feel that this would go beyond the purpose of this article. It will be cited with limitations.

• Comments 13: common reference intervals for a Region or a country to overcome some of the problems of cost and complexity, this is not mentioned.

Response 13: For some time now, there have been reports of initiatives involving harmonized reference values at the regional or national level (Jones 2014, Koerbin 2016, RCPA 2025, Ceriotti 2007), and there is a call for their widespread implementation. These are interesting initiatives, but they are applicable only in certain local contexts. Current guidelines do not yet incorporate these approaches for laboratories in general. Certainly, harmonizing reference intervals across different laboratories would require comparability of testing methods and the populations served. It would reduce differences between laboratories, but it would not address any of the difficulties described regarding the dichotomous use of reference intervals in medical practice. A brief passage has been added to the text: “As an alternative to the reference ranges established by manufacturers or large laboratories, the use of regionally harmonized reference ranges has been proposed [Badrick, RCPA]. This article does not discuss the advantages and limitations of this approach, which is interesting but not available in many countries or for many tests due to the need to meet stringent prerequisites. [Ceriotti 2007] SIPMeL M2-2, like CLSI EP45, does not yet propose this solution, partly because it is not available in the relevant geographic area.”

• Comments 14: Are there limitations in the paper?

Response 14: The topic of decisions based on the results of measurements or tests is very broad and has been addressed by numerous sources in extensive and in-depth documents. This review seeks to bridge the gap between the approaches of testing laboratories and medical laboratories, with the aim of stimulating reflection on the value of limits and reference ranges that can lead to improved practical guidance for laboratory users, particularly those in the medical field. For the sake of brevity and to focus on certain aspects of the topic, other aspects regarding limits and ranges have not been addressed. The list would be very long; among these, details on differences among decision rule with pass/fail using simple acceptance, decision rule with pass/fail using guard band, decision rules with conditional or inconclusive results, decision rule specifying a two stage procedure, acceptable value for standard uncertainty, determining the size of the guard band and acceptance limit, producer and consumer risk, selection of reference Individuals, calculation of sample size, statistical data analysis, outlier handling, confidence intervals, the need o oversight of a biostatistician, handling of skewed data, presentation of RIs, personalized and predictive reference ranges. However, each of these topics can be explored in greater depth in the sources listed in the bibliography. A section titled “Limitations” has been added.

• Comments 15: Is reference 38 the correct reference for the text?

Response 15: CLSI guideline EP33 (delta checks) is linked to 7.4.1.7(d)(4) regarding trends in results or significant changes over time. The connection is not explicitly stated in the documents, nor is it mentioned by everyone, but in our view it is, in fact, substantial.

Reviewer 2 Report

Comments and Suggestions for Authors

• The paper demonstrates the value of appropriate expression of measurement results, both in testing laboratories and in medical biochemical laboratories. The author compares the requirements of the ISO 17025 and ISO 15198 standards that apply to testing laboratories and medical biochemical laboratories, and related to the interpretation of results. The author explains the differences in expression and the importance of clearly stating critically important clinical values ​​for the interpretation of results. He also discusses the uncertainty of measurement results as a quantitative representation of the quality of the results. He also states that the Italian Society of Clinical Pathology and Laboratory Medicine, National Quality Commission has just incorporated these recommendations of the standard into its routine.
• The paper is original and relevant to the field. The author presents an additional summarized comparison of the requirements of the standards related to the result as the final product of the laboratory process. He also points out that this is not the end of determining the result, but the beginning of the next post-analytical process, which is closest to the doctor and on which successful communication between the laboratory and the doctor depends, and on which clinically significant decisions depend. This is precisely what is being used to fill the gap that exists regarding the standardization of extra-analytical processes.
• The paper discusses the recommendations of various guides for the interpretation of results, related to reference values, the way in which they are determined, directly or indirectly, which advantages are possessed, and additionally discusses the recommendations for tests developed in the laboratory, without commercial instructions from the manufacturer, and states how in these cases the results can be interpreted according to the standard analytical characteristics of the test, and without official instructions from the manufacturer of the commercial reagent.
• In my opinion, the methodology is complete and I would have no further suggestions. The author has comprehensively stated all the current benefits and limitations regarding the value of the results. Additionally, the author emphasizes the importance of the document used in his country, i.e., he cites the recommendations of the Italian Society of Clinical Pathology and Laboratory Medicine, National Quality Commission.
• As for the conclusion itself, it has been omitted as such in this paper. It would be recommended that the author summarize in one paragraph the conclusions drawn from this paper. Although in the last chapter he has listed in detail everything that has been written about.
• References are appropriate.
• As for the tables, they are completely fine, clear and specific, and as for the figures, they are completely original and easy to understand.

Author Response

General comment from the Author: The reviewers' comments accurately reflect the range of reactions—from enthusiastic approval to harsh criticism—that we would have expected from a group of laboratory specialists with diverse backgrounds and, consequently, very different perspectives. To us, they serve as evidence of the value of a contribution that compares objective realities from a perspective that is not uncritically tied to traditional practice. Answering all of the Reviewers' questions turned out to be very time-consuming and labor-intensive, almost like writing a new article.

• Comments 1: The paper is original and relevant to the field.

Response 1: We would like to thank the Reviewer for all the kind words of appreciation.

• Comments 2: As for the conclusion itself, it has been omitted as such in this paper. It would be recommended that the author summarize in one paragraph the conclusions drawn from this paper. Although in the last chapter he has listed in detail everything that has been written about.

Response 2: Chapter 8 of the article outlines the main concepts that can be derived from the analysis of the sources. As suggested by the Reviewer, a concluding paragraph has been added.

Reviewer 3 Report

Comments and Suggestions for Authors

This narrative review compares how ISO 17025 (testing/calibration laboratories) and ISO 15189 (medical laboratories) handle decision rules for measurement results. The author frames the two standards as taking "diametrically opposite" approaches — testing labs convey uncertainty for downstream conformity decisions, while medical labs provide reference intervals (RI) and clinical decision limits (DL) to support clinical decision-making. The bulk of the paper focuses on the medical-laboratory side, reviewing CLSI guidelines (EP44, EP45, H20), critiquing the feasibility of traditional direct methods for establishing RIs, and advocating for indirect methods based on real-world data and for the SIPMeL M2-2 Recommendations (which the author co-developed).

My recommendation is rejection or major revision.

Here are my major Concerns

1. The rationale for comparing these two standards is not established. ISO 17025 and ISO 15189 serve different purposes and different communities. Why should they be compared at all? The author asserts a "diametrically opposite" contrast but never explains why this contrast is informative or actionable. Are the two frameworks ever applied to the same laboratory or decision? Should one learn from the other, and in which direction? Without an answer, the paper reads as two loosely connected reviews rather than a coherent comparative one — an impression reinforced by the imbalance in coverage (one page on ISO 17025, the rest on ISO 15189). This concern may partly reflect my own limited background, but precisely for that reason the author needs to make the case explicitly in the main text.

2. Figures need polishing. In Figure 1, the meaning of *T* (tolerance) is unclear, and *A* and *T* should be drawn in distinct colors matching their labels so the nested relationship is visible at a glance. Figure 2 should be split into two panels, since RI and DL are alternative frameworks, not parts of one. Overall, the figures look rough and should be redrawn at publication quality.

3. The conclusion is unclear, and the supporting evidence is uneven. After reading the paper, I cannot tell whether the author's central recommendation is to abandon traditional RIs, shift to indirect methods, adopt SIPMeL M2-2, or call on standards bodies to revise their guidance. The critique of CLSI direct methods leans heavily on the author's own SIPMeL document and a single conference poster; the endorsement of indirect methods does not engage with documented limitations; and the dismissal of race/ethnicity as a stratification factor is made without citation despite an active literature on this question. A review of this scope needs a clearer take-home message and a more even evidence base.

Author Response

General comment from the Author: The reviewers' comments accurately reflect the range of reactions—from enthusiastic approval to harsh criticism—that we would have expected from a group of laboratory specialists with diverse backgrounds and, consequently, very different perspectives. To us, they serve as evidence of the value of a contribution that compares objective realities from a perspective that is not uncritically tied to traditional practice. Answering all of the Reviewers' questions turned out to be very time-consuming and labor-intensive, almost like writing a new article.

• Comments 1: The rationale for comparing these two standards is not established.

Response 1: It is much appreciated that the Reviewer acknowledges having a “limited background” on the topic of the article. We would be happy to do our small part to help the Reviewer gain a better understanding of the subject, and we thank him for his very precise comments, despite this limitation. It is hoped that the revisions made to the manuscript in response to the reviewer’s comments will make it more accessible to readers who are not experts in the subject.

The relationship between ISO 17025 and ISO 15189, between testing laboratories (particularly chemical, microbiological, and toxicological laboratories) and medical laboratories, is highly complex; it is the subject of extensive literature and constitutes a significant part of our direct experience. In some countries, medical laboratories can obtain either ISO 17025 or ISO 15189 accreditation. We have seen ISO 17025-accredited laboratories expand their activities into the medical sector and obtain ISO 15189 accreditation. In some cases, for the very same tests. The issue is therefore practical in nature, but also theoretical, as it prompts speculative reflections on the nature of laboratory activities and their metrological classification. As Possolo has already described, for example, regarding the similarities and differences between laboratories in the two categories in terms of measurement uncertainty. A consideration such as this is added in the introduction.

• Comments 2: contrast informative or actionable

Response 2: The article highlights a difference that exists in reality; it does not promote it but rather presents it as a topic for reflection. Criticism of the traditional approach to RIs, alongside the issue of measurement uncertainty, is present in the scientific literature. Authors such as Posssolo, Badrick, El-Khoury, Theodorsson, and others can be cited. The difference in approach is only apparent when the two models are placed side by side; otherwise, each community remains confined to its own field: ISO 17025 aims to cast doubt on the result, while ISO 15189 describes the traditional practice in which the laboratory seeks to provide the laboratory user with a simple interpretive solution (“dichotomic” following Badrick) so that action can be taken as soon as possible, without giving it too much doubt. These concepts are presented throughout the revised version of the manuscript, particularly in the introduction and conclusions.

• Comments 3: Two models applied to the same experiment or the same decision? Should one model inform the other, and in what way?

Response 3: In everyday practice, the two models are not applied simultaneously; however, both are based on the same metrological principles with regard to measurement results. Laboratories are not required to delve into this comparison, but researchers involved in metrological theory and accreditation requirements are. We have not found many publications that compare the two approaches. The sources found are the main inspiration for this article and are listed in the Bibliography.

• Comments 4: the imbalance in coverage (one page on ISO 17025, the rest on ISO 15189).

Response 4: The article devotes less space to testing laboratories than to medical laboratories. The decision limits addressed by ISO 17025, ISO Guide 99-4, and Eurachem are based on sound statistical principles, are simpler, and have been less criticized in the literature, whereas those in ISO 15189 are more problematic and have been more heavily criticized.

The section devoted to medical laboratories is much longer than that for ISO 17025, because the issue of medical laboratories is addressed very extensively in the literature, which brings together a vast array of experiences and diverse opinions, along with proposed solutions of radically different types. The comparison between the two situations serves as a basis for critical, perhaps “philosophical,” reflection, and may in the future be brought together into a single theory (see Possolo, IUPAC NIST Metrology 62 (2025) 042101).

• Comments 5: Figures need polishing. In Figure 1, the meaning of *T* (tolerance) is unclear, and *A* and *T* should be drawn in distinct colors matching their labels so the nested relationship is visible at a glance.

Response 5: Figure 1 was redrawn in accordance with the reviewer’s instructions. “Tolerance” is described in the references; a more detailed discussion—which is not apparent from the synthesis in the figure—would be beyond the scope of this article. *A* and *T* have been colored differently and repositioned for better clarity.

• Comments 6: Figure 2 should be split into two panels,

Response 6: Figure 2 is intended not only to illustrate the two approaches but also to compare them directly, with measurement (M) serving as the common link. Therefore, it is preferable to keep them in a single figure rather than separating them.

• Comments 7: the figures look rough and should be redrawn at publication quality.

Response 7: Other reviewers have deemed the figures adequate and effective. Precisely because of the theoretical and metrological nature of the subject—which is quite sophisticated—the figures were designed to be as simple as possible, almost elementary, to help the reader grasp the issue, despite the distance some may feel from it and the influence of long-established practices and concepts.

• Comments 8: The conclusion is unclear, and the supporting evidence is uneven. I cannot tell whether the author's central recommendation is to abandon traditional RIs, shift to indirect methods, adopt SIPMeL M2-2, or call on standards bodies to revise their guidance.

Response 8: This article is not intended to issue definitive recommendations on RIs, a difficult task even for qualified bodies (such as CLSI or ISO), which in fact remain cautious. Scientific progress is slow and relies on contributions from various sources. The topic was also covered very well in a recent IFCC webinar (April 29, 2026, “Health Equity in Laboratory Medicine”) and in an ADLM workshop (Health Equity in the Laboratory: Re-evaluating the Role of Sex and Race in Reference Interval Determinations) (https://myadlm.org/cln/cln-daily/2024/redefining-reference-intervals-for-health-equity), with interesting, albeit not definitive, proposals.

This article is not a complete and exhaustive review of all sources, including experimental ones, but aims to remain objective, draw attention to some key sources of guidelines, and encourage laboratories to critically review even well-established practices. This point is included among the limitations in the conclusions. The author’s sympathy for the critical voices regarding RIs and the slow evolution of CLSI is evident. However, the article aims to present concrete evidence to give readers the means to form their own opinions, without being overly prescriptive.

• Comments 9: The critique of CLSI direct methods leans heavily on the author's own SIPMeL document and a single conference poster;

Response 9: The SIPMeL Recommendations document was not authored by a single individual, but is the result of extensive work by several Study groups and a Committee, and was approved at the highest level by the Society’s leadership. It is a very lengthy document, with a highly detailed bibliography, which seeks to bring together different perspectives and significant cases described in applied research articles. It is not an individual article; otherwise, it would have been cited as such. These same groups are actively participating in the CLSI’s revision of documents EP44 and EP45, alongside others.

The critique of CLSI is divided into two parts: one on direct methods and one on the comparison of methods. The critique of direct methods is extensively discussed in the SIPMeL Recommendations, with numerous citations, and we can now see it addressed in a very recent and highly authoritative article (Badrick, T., El-Khoury, J. M., & Theodorsson, E, Ref. 36). For the second part, two peer-reviewed articles were cited as sources for the criticisms (supported by CLSI), which in turn contain other important references in the literature (Ref. 33 and 34).

• Comments 10: the dismissal of race/ethnicity as a stratification factor is made without citation despite an active literature on this question

Response 10: This article is not intended to be a complete, exhaustive review of all sources on every point, but rather a selection of passages of particular practical value or general theoretical significance. Going into excessive detail about the sources (which are, in any case, readily available) would dilute the main message. Two specific references (among many) have nevertheless been included (Ref. 16 and 17), without repeating those already cited in the Recommendations, and the bibliography has therefore been renumbered. The topic was the subject of a recent IFCC seminar (April 29, 2026, “Health Equity in Laboratory Medicine,” which was very effective), where concrete cases were described, and of an ADLM seminar (“Health Equity in the Laboratory: Re-evaluating the Role of Sex and Race in Reference Interval Determinations”). (https://myadlm.org/cln/cln-daily/2024/redefining-reference-intervals-for-health-equity). We are waiting for the content of these events to be documented as soon as possible so that we can use it as a source.

• Comments 11: the endorsement of indirect methods does not engage with documented limitations;

Response 11: Criticism of traditional and indirect methods is widespread in the literature, as in the recent article by Badrick, El-Khoury, and Theodorsson (Ref. 36), which argues that RIs should not be considered valid for every situation and that indirect reference intervals depend on at least a rough separation of healthy and diseased individuals using clinical or statistical techniques based on Gaussian-distributed subpopulations. This article does not aim to weigh the pros and cons of indirect methods based on a broad body of literature. However, it notes that several sources indicate that indirect methods are suitable for verifying RIs.

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Author(s),

I read this manuscript with great interest. It is a timely, relevant, and scientifically valuable contribution to the field of laboratory medicine, metrology, and ISO-accredited laboratory practice. The manuscript addresses an important and often insufficiently discussed distinction between decision rules in ISO/IEC 17025 testing laboratories and the interpretation of examination results in ISO 15189 medical laboratories. The discussion is well-informed, conceptually clear, and supported by highly relevant standards, guidelines, and recent literature.

The article is particularly strong in its comparative framing of measurement uncertainty, conformity assessment, reference intervals, clinical decision limits, and real-world data approaches. It provides a useful synthesis for laboratory professionals, assessors, and clinicians involved in the interpretation and reporting of laboratory results.

Overall, this is a strong and useful manuscript that addresses an important practical and conceptual issue in accredited laboratory medicine. The article is scientifically sound, well-referenced, and likely to be valuable to readers interested in ISO 15189, ISO/IEC 17025, reference intervals, clinical decision limits, and real-world data.

I suggest the following minor revisions:

1 - Clarify the main objective in the Abstract and Introduction. The central message of the manuscript is strong, but the Abstract could more explicitly state that the article aims to compare the logic of decision rules in testing laboratories with the interpretive framework used in medical laboratories. This would help readers immediately understand the article’s contribution.

2 - Slightly strengthen the concluding message. The final section is informative, but it could be strengthened by adding a brief final paragraph emphasizing the practical implications for ISO 15189-accredited medical laboratories, particularly the need to distinguish reference intervals from clinical decision limits and to avoid treating reference intervals as diagnostic thresholds.

3 - Review or remove Figure 4. Figure 4, “The difficulty of assigning an individual to a specific cluster,” should be reconsidered. In its current form, it does not appear to add substantial value to the argument and may distract from the otherwise strong conceptual flow of the manuscript. The authors may either remove it or replace it with a more informative figure directly illustrating the limitations of rigid partitioning in reference interval studies.

4 - Standardize abbreviations and terminology. The manuscript would benefit from careful standardization of terms such as reference interval, RI, decision limit, DL, clinical decision limit, and biological reference interval. Once defined, abbreviations should be used consistently throughout the manuscript.

5 - Ensure consistency and completeness in references to standards and guidelines. The manuscript cites several important standards and guideline documents, including ISO, CLSI, ILAC, EURACHEM, IFCC, and SIPMeL documents. The authors should ensure that all references are complete, consistently formatted, and, where applicable, clearly identified as published, projected, draft, or forthcoming documents.

Comments on the Quality of English Language

Check minor wording and typographical issues. A light English-language revision is recommended. Examples include minor grammatical issues such as “the author declare” instead of “the author declares,” “in spite to” instead of “despite” or “in spite of,” and occasional double punctuation. These are minor issues and do not affect the scientific merit of the article.

Author Response

General comment from the Author: The reviewers' comments accurately reflect the range of reactions—from enthusiastic approval to harsh criticism—that we would have expected from a group of laboratory specialists with diverse backgrounds and, consequently, very different perspectives. To us, they serve as evidence of the value of a contribution that compares objective realities from a perspective that is not uncritically tied to traditional practice. Answering all of the Reviewers' questions, turned out to be very time-consuming and labor-intensive, almost like writing a new article, even though it's pleasant.

• Comments 1: The manuscript addresses an important and often insufficiently discussed distinction between decision rules in ISO/IEC 17025 testing laboratories and the interpretation of examination results in ISO 15189 medical laboratories.

• Comments 2: It provides a useful synthesis for laboratory professionals, assessors, and clinicians involved in the interpretation and reporting of laboratory results.

Response 2: Thank you. The reviewer has hit the nail on the head regarding the purpose of the article.

• Comments 3: Overall, this is a strong and useful manuscript that addresses an important practical and conceptual issue in accredited laboratory medicine.

Response 3: Thank you. The reviewer has hit the nail on the head regarding the purpose of the article.

• Comments 4: Clarify the main objective in the Abstract and Introduction. The central message of the manuscript is strong, but the Abstract could more explicitly state that the article aims to compare the logic of decision rules in testing laboratories with the interpretive framework used in medical laboratories. This would help readers immediately understand the article’s contribution.

Response 4: A few sentences have been added in the Abstract and Introduction.

• Comments 5: Slightly strengthen the concluding message. The final section is informative, but it could be strengthened by adding a brief final paragraph emphasizing the practical implications for ISO 15189-accredited medical laboratories, particularly the need to distinguish reference intervals from clinical decision limits and to avoid treating reference intervals as diagnostic thresholds.

Response 5: The concluding message has been reinforced. Dichotomization (healthy or sick) has been identified as the main flaw in the traditional use of RIs.

• Comments 6: Review or remove Figure 4. Figure 4, “The difficulty of assigning an individual to a specific cluster,” should be reconsidered. In its current form, it does not appear to add substantial value to the argument and may distract from the otherwise strong conceptual flow of the manuscript. The authors may either remove it or replace it with a more informative figure directly illustrating the limitations of rigid partitioning in reference interval studies.

Response 6: Figure 4 and the accompanying text illustrate a phenomenon that is the opposite of that analysed in many guidelines and on which many laboratories focus, a point that warrants specific emphasis. In addition to the determination and verification of RIs, problems also arise in their use. The studies analyzed in the review and in the Recommendations have shown not only that RIs based on specific groups of individuals are not suitable for individuals belonging to other groups, but that the reverse is also true. Figure 4, the colors, and the accompanying text aim to highlight a concept that is not always intuitive: when an individual visits a doctor or a laboratory, it is not always easy to assign them to a specific ethnic, geographic, or social group. This becomes increasingly difficult with population mobility. This further adds uncertainty, reduces the hypothetical utility of RIs distinguished by certain categories, and thus of RIs in general. To reinforce this message, we propose retaining Figure 4.

• Comments 7: Standardize abbreviations and terminology. The manuscript would benefit from careful standardization of terms such as reference interval, RI, decision limit, DL, clinical decision limit, and biological reference interval. Once defined, abbreviations should be used consistently throughout the manuscript.

Response 7: abbreviations RIs and Dls were used in the entire manuscript, with the exception of sentences from other sources

• Comments 8: Ensure consistency and completeness in references to standards and guidelines. The manuscript cites several important standards and guideline documents, including ISO, CLSI, ILAC, EURACHEM, IFCC, and SIPMeL documents. The authors should ensure that all references are complete, consistently formatted, and, where applicable, clearly identified as published, projected, draft, or forthcoming documents.

Response 8: All references were double-checked and, where necessary, completed.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I was happy to accept the revised document without further qualification.

Reviewer 3 Report

Comments and Suggestions for Authors

Thanks for addressing the comments