Search Results (2,803)

Background/Objectives: Prothrombin time (PT), international normalized ratio (INR), and activated partial thromboplastin time (aPTT) are routinely used coagulation assays, and analyzer–reagent differences may affect result comparability. This study evaluated analytical comparability between the Sysmex CS-2500 System using Siemens reagents and the Tokra Medical NOVAE II for PT, INR, and aPTT. Methods: Residual routine citrated plasma specimens were measured on both systems. The CS-2500 was designated as the comparator system. Passing–Bablok regression and Bland–Altman analysis were used as the primary method-comparison approaches; Pearson and Spearman correlations and exploratory categorical agreement were secondary analyses. Results: Fifty paired measurements were analyzed for PT and INR and 54 for aPTT. For all three parameters, the 95% confidence interval (CI) for the Passing–Bablok intercept included 0 and the 95% CI for the slope included 1, providing no statistically supported evidence of constant or proportional bias by regression. Mean paired differences (NOVAE II minus CS-2500) were +1.27 s for PT, +0.023 for INR, and +2.32 s for aPTT. The 95% limits of agreement were −0.15 to +2.69 s for PT, −0.112 to +0.159 for INR, and −1.70 to +6.33 s for aPTT. Categorical agreement was influenced by analyzer-specific reference intervals and by the low prevalence of abnormal results. Conclusions: The two analyzer–reagent systems showed positive analytical associations, but the magnitude and dispersion of paired differences varied by assay. Because no clinical equivalence margins were prespecified and markedly pathological or therapeutic-range samples were sparsely represented, these findings support analytical comparison and local verification but do not establish clinical interchangeability. Full article

Accurate modeling of the tooth friction coefficient is central to analyses of efficiency, vibration, and durability in enclosed gear drives. Physics-based models describe these contacts using a large set of coupled thermal, contact, and lubrication laws whose individual parameters have uncertainties that are difficult to propagate. This study proposes a compact alternative: the HAF model, a three-parameter phenomenological description of the friction coefficient as a function of the slide-to-roll ratio (SRR). The three parameters have distinct tribological interpretations: h (hysteresis) governs the steepness of the sigmoidal transition, a (attrition) governs the slope of the plateau, and ν (friction level) governs the overall magnitude. The model is calibrated using nonlinear regression with fourteen two-disc traction curves acquired with a one-factor-at-a-time (star) design around a reference operating point (1.6 GPa, 80 °C, and 20 m/s): the contact pressure (1.2, 1.6, and 1.9 GPa), the injection temperature (40, 80, and 100 °C), and the mean speed (10, 20, and 30 m/s) are each varied in turn, for both smooth and rough discs. Parameter uncertainty is quantified using the residual-resampling bootstrap (BIG) established in a companion paper and applied over 10⁵ iterations; it yields near-Gaussian, weakly correlated parameter distributions. The three HAF parameters are then expressed as linear functions of load, temperature, speed, and roughness; least-squares inference across the fourteen conditions shows that eleven of the fifteen regression coefficients differ significantly from zero at the 5% level, with roughness having the strongest effect on the friction level (t = 7.98). Substituting these laws into the HAF equation and reoptimizing the resulting expression globally yields a single closed-form model that reproduces the measured friction coefficient with a residual spread of σ ≈ 0.001 in friction-coefficient units (R² ≈ 0.996) and approximately Gaussian, zero-mean, and homoscedastic residuals with no evident systematic structure. Being differentiable and equipped with bootstrap confidence intervals, the model predicts friction throughout the tested operating envelope—across which the maximum friction coefficient varies by a factor of eight, from 0.0049 to 0.0388—and supports gradient-based optimization of low-friction operating conditions. The contribution of this study is a compact, interpretable, and statistically characterized predictive law for tooth friction, expressed in closed form as a function of the operating conditions and of the surface state. Full article

Probabilistic models of glued laminated timber are a required input to structural reliability analysis, and the JCSS Probabilistic Model Code is the reference most analyses adopt without independent verification. This paper reports an experimental programme of 61 small clear-wood specimens of GL24h glulam produced in Croatia, cut from three parent elements from one producer, delivered together as a single lot, covering bending, tension and compression parallel to grain, shear of wood and of the adhesive line, compression perpendicular to grain, and finger joints in tension and bending. All eight strength properties are tested against the reference model with confidence intervals and a family-wise error correction across the eight comparisons. Exactly one deviation survives: the coefficient of variation (COV) of tensile strength parallel to grain is 0.339 against the reference 0.180, with a Holm-adjusted p = 0.0064; no other property is distinguishable from the reference. The measured density COV of 0.026, against a reference value of 0.10, shows directly that the specimens are a cluster sample from three parent elements rather than independent draws from the GL24h population, which makes the elevated tensile scatter the more notable, since clustering suppresses observed variability rather than inflating it. The reliability consequence is then shown to depend on an assumption usually left implicit. Holding the characteristic value at the declared 19.2 MPa, as grading enforces, the reliability index of a tension-critical element falls from 3.30 to 3.09; holding the mean constant, it falls to 2.41. The absolute values depend on the load-duration class assumed for snow, but the contrast between the two treatments does not. Carrying the sampling uncertainty of the COV estimate through the calculation lowers these to predictive values of 2.88 and 1.82. The conclusion is correspondingly narrow: elevated tensile variability matters for the assessment of existing structures, where the mean is measured rather than declared, and for reliability studies that adopt generic parameters and vary only dispersion; it matters little where grading against a fractile is active. Full article

Simultaneous land-use changes can reinforce or offset one another, so urban expansion alone may not explain changes in catchment-scale runoff potential. This study examined long-term changes in land-use composition and in estimated relative runoff potential across five sub-catchments in the Kameoka Basin, Japan. Land use at eight time points spanning approximately 130 years (1890s–2021) was reconstructed from Meiji-period historical topographic maps and Land-Use Subdivision Mesh Data. The area-weighted runoff coefficient ($\overline{C}$), derived from land-use-specific coefficients assigned with reference to Japanese technical standards and area proportions rather than observed rainfall–runoff data, was used as a proxy for relative runoff potential. Its change was decomposed into land-use contributions summarized as $\mathrm{Net} ∆\overline{C}$, total absolute contribution (Gross), and the net-to-gross ratio, complemented by interval-by-interval, transition-based, and coefficient-sensitivity analyses. Urban land increased by 5.1–16.0 percentage points, whereas $\mathrm{Net} ∆\overline{C}$ ranged from −0.004 to +0.037. Three contrasting contribution patterns were observed: structural inertia in Nanatani, dynamic offset in Chiji and Inukai, and development-driven increases in Toshitani and Sogadani. These contrasts remained identifiable under plausible alternative coefficients, although offsetting in Sogadani was more coefficient-sensitive. The approach may provide a diagnostic basis for differentiated sub-catchment-scale land management. Full article

The study was conducted to establish the thermoneutral zone (TNZ) of Murrah buffalo calves under precisely regulated environmental conditions. Six healthy calves (8–10 months) were exposed to progressively decreasing (24–15 °C; Temperature-Humidity Index (THI): 72.45–58.98) and increasing (25–40 °C; THI: 73.49–90.32) ambient temperatures with 3 °C intervals in a psychrometric chamber. Each exposure was maintained for 10 consecutive days under cyclic conditions (12 h exposure and 12 h thermoneutral recovery). Physiological responses and body surface temperature (BST) were recorded, and blood samples were collected on day 10 at 1500 h. Segmented regression analysis was performed using the SegReg (Oosterbaan, 2017) software program to identify lower and upper critical temperatures (LCT, UCT) and corresponding THI thresholds. LCTs ranged from 18.06 to 19.14 °C across different responsive parameters, with breakpoints (BPs) at 18.60 °C (SE_BP = 0.634) for pulse rate (PR), 18.15 °C (SE_BP = 0.945) for haemoglobin, 18.15 °C (SE_BP = 0.189) for lymphocytes, 18.24 °C (SE_BP = 0.404) for granulocytes, 19.14 °C (SE_BP = 1.09) for reactive oxygen species (ROS), 18.15 °C (SE_BP = 23.9) for superoxide dismutase (SOD), and 18.06 °C (SE_BP = 4.2) for cortisol; no distinct LCT was detected for respiratory rate (RR), rectal temperature (RT), total leukocyte count (TLC), or heat shock protein (HSP) 70/HSP90 expression. BST at different locations exhibited an LCT between ~20 and 21 °C. UCTs for PR, RR and RT were observed at 28.9 °C (SE_BP = 0.892), 28.6 °C (SE_BP = 0.843) and 29.2 °C (SE_BP = 1.16), respectively. Neither BST nor erythrocytic parameters exhibited a distinct UCT; however, BST increased progressively with increasing exposure temperature. TLC, lymphocyte and granulocyte % showed UCTs of 28.15 °C (SE_BP = 0.753), 28.15 °C (SE_BP = 0.497) and 32.65 °C (SE_BP = 14.20), respectively. The UCT for cortisol was observed at 28.15 °C (SE_BP = 5.52), whereas ROS and SOD showed UCTs of 28.75 °C (SE_BP = 4.67) and 34.15 °C (SE_BP = 6.55), respectively. HSP70 and HSP90 exhibited breakpoints at 35.35 °C (SE_BP = 1.32) and 34.30 °C (SE_BP = 2.11), respectively. Integration of key physiological and systemic responses (excluding BST) indicated a TNZ ranging from 19.14 °C to 28.15 °C. These findings provide a multi-level characterization of thermophysiological responses in buffalo calves and support the use of integrated biological indicators for defining thermoneutral conditions under controlled environments. The estimated TNZ of 19.14–28.15 °C provides a practical reference for managing Murrah buffalo calves. Producers should monitor housing temperature and consider ventilation, shade and air movement when temperatures approach or exceed ~28 °C while providing protection from cold when temperatures fall below ~19 °C. This may help reduce thermal strain and maintain normal physiological function. Full article

Ward cooling is controlled by a single thermostat, yet whether it represents the mean room temperature is rarely evaluated. Existing virtual sensing reconstructs values at predetermined locations rather than identifying which location should be the reference. This study locates that reference point, tests its stability as the thermostat and occupant move, and estimates it from existing control signals. Air temperature and humidity were measured at 5-min intervals at 21 plan locations and three heights in a 16.03 m² ward-type test room without mechanical ventilation, a 70 W heated cylinder as occupant, in six configurations. The instantaneous spatial deviation reached 4.5 °C. Against the room mean, the thermostat gave a slope of only 0.52 and read high by up to 0.86 °C, whereas one point gave 0.98 and was selected in five of six cases; training-window-only selection returned the same point. Estimating it from four control signals cut the thermostat’s tracking error by 41%, from 0.291 to 0.172 °C, and reproduced the point to within 0.222 °C when trained on five cases and tested on the sixth. Representativeness tracks the deviation field, which was invariant across configurations, so the point needs to be identified once per room. Comfort and energy were not measured. Full article

Adaptive cruise control (ACC) tracks a time-gap reference that trades efficiency against spacing safety; in practice this gap is fixed offline, although the safest choice depends on the closing speed and on the reliability of the perception that supplies the lead-vehicle state. We present GL-TGS-v2, a guarded, interpretable supervisor that selects the time-gap reference of an adaptive model predictive controller (MPC) online from tracked lead-vehicle kinematics. The supervisor is a decision-tree distillation of a calibrated adaptive expert, wrapped by a perception-aware safety shield; its only authority is the time-gap reference, so it retrofits onto an existing controller without re-opening the inner loop. We evaluate it in closed loop on a frozen stack that couples a YOLO11 detector, a joint probabilistic data association (JPDA) tracker, and the adaptive MPC, with documented runtime and per-run provenance gates. In a hard lead-braking scenario (ten runs per method), GL-TGS-v2 matches the expert at a matched mean time gap and improves minimum relative distance over fuzzy and fixed-gap baselines by 3.3–5.2 m, with 95% confidence intervals excluding zero, lower target loss, and no collisions. Benign testing shows no regression, while shield ablation characterizes the guard as an auditable protective override. Full article

Background: Accurate interpretation of neonatal complete blood count (CBC) parameters is vital for managing life-threatening conditions in newborns. However, clinical decisions in Eastern Sudan frequently rely on non-local Western-derived or manufacturer-provided reference intervals (RIs), thereby risking diagnostic errors. Therefore, this study aimed to establish the local neonatal hematological RIs for healthy, term newborns in Eastern Sudan. Methods: This hospital-based, cross-sectional study was conducted at New Halfa Hospital. Umbilical cord blood samples were collected from 250 healthy term singleton neonates born to mothers with uncomplicated pregnancies and deliveries. Samples were analyzed using a Sysmex KX-21 hematology analyzer (Sysmex, Kobe, Japan). In accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines, sex-specific 95% RIs were initially estimated, followed by assessment of whether sex-specific partitioning was warranted by calculating the central 2.5th and 97.5th percentiles. Differences in the distributions of hematological parameters between males and females were evaluated using the Mann–Whitney U test. Results: Of the total 250 newborns (123 males, 127 females), no statistically significant differences were found between male and female newborns for any of the eleven evaluated hematological parameters, justifying the pooling of data to establish unified RIs. The established 95% pooled RIs and medians were as follows: white blood cell (WBC) count: 6.33–20.90 × 10³/µL (median: 11.15 × 10³/µL); red blood cell (RBC) count: 2.91–5.04 × 10⁶/µL (median: 4.02 × 10⁶/µL); hemoglobin: 11.20–16.52 g/dL (median: 13.90 g/dL); hematocrit: 36.30–55.30% (median: 43.70%); mean cell volume (MCV): 93.41–127.53 fL (median: 109.70 fL); platelets: 49.20–438.68 × 10³/µL (median: 251.00 × 10³/µL); mean platelet volume (MPV): 7.36–11.55 fL (median: 9.30 fL); platelet distribution width (PDW): 16.10–19.37% (median: 16.90%). Conclusions: The results of this study provide preliminary locally derived neonatal CBC RIs for Eastern Sudan. The absence of statistically significant sex differences in this sample supports consideration of pooled neonatal RIs. The lower reference boundaries for hemoglobin, leukocytes, and platelets identified here differ markedly from Western-derived values and those reported in high-altitude cohorts, underscoring the critical clinical need to use these population-specific intervals, which may reduce inappropriate classification arising from the use of non-local reference intervals. Full article

Background/Objectives: Congenital heart disease (CHD) is a major cause of congenital morbidity and mortality, but evidence from public pediatric cardiology services in Brazil remains limited. This study aimed to characterize the clinical and epidemiological profile of children and adolescents referred to a public pediatric cardiology service in Southern Brazil, including referral patterns, diagnostic findings, and healthcare utilization, and to explore factors associated with age-appropriate development. Methods: In this cross-sectional study, medical records of patients aged 0–17 years referred to and evaluated at a public university hospital in Rio Grande, Rio Grande do Sul, were retrospectively reviewed. Demographic, referral, clinical, diagnostic, hospitalization, family history, school performance and developmental data were extracted. Groups were compared using the chi-square or Fisher’s exact test. Poisson regression with robust variance estimated prevalence ratios in an exploratory secondary analysis of age-appropriate development. Sensitivity analyses were performed excluding isolated patent foramen ovale, applied a stricter structural CHD definition, restricted the adjusted analysis to patients who underwent echocardiography, and modeled age using clinical categories. Results: Among 263 referred patients, CHD was confirmed in 128 (48.7%); among these, 84% had acyanotic and 16% had cyanotic CHD. Suspected heart disease was the most frequent reason for referral (64%). Echocardiography was performed in all patients with confirmed CHD compared with 24% of those without CHD, and hospitalization was more frequent among patients with confirmed CHD (52% vs. 21%). In the exploratory adjusted analysis, no statistically significant overall association was detected between CHD category and age-appropriate development (p = 0.122). The estimate for cyanotic CHD suggested a lower prevalence than no CHD, but the confidence interval included the null and the estimate was imprecise (adjusted PR 0.745; 95% CI 0.553–1.002). Age at evaluation showed a small inverse association. Sensitivity analyses yielded estimates in the same direction as the primary model, while the overall CHD-category association was statistically significant only in the analysis restricted to patients who underwent echocardiography. Conclusions: Under the record-based operational definition, CHD was confirmed in nearly half of the referred patients, predominantly acyanotic. These findings characterize the clinical and epidemiological profile and healthcare demands of children reaching specialized pediatric cardiology care in southern Brazil and may support improvements in referral pathways and planning of specialized care for patients with CHD. Full article

To conduct a scientific and comprehensive analysis of the spontaneous combustion tendency of sulfide ores and improve the safety production level of sulfur mines, an indicator system for determining the spontaneous combustion tendency of sulfide ores and a comprehensive classification standard for the spontaneous combustion tendency of sulfide ores were constructed. Based on this, a multidimensional information comprehensive analysis model for ore spontaneous combustion tendency was constructed by combining the interval analytic hierarchy process (IAHP) and the improved interval approximation analysis method. The interval judgment matrix was constructed by the interval analytic hierarchy process, and the weight of the spontaneous combustion tendency for evaluation indicators was calculated. By improving the interval approximation analysis, the indicators of the ore spontaneous combustion tendency were analyzed in the form of interval numbers, and the information potential was deeply explored to obtain multidimensional information such as the grade of the ore spontaneous combustion tendency and the reliability of the ore spontaneous combustion tendency, and then the comprehensive grade of the ore spontaneous combustion tendency was determined. By using this model, a multidimensional information analysis was conducted on the spontaneous combustion tendency of each ore layer in a certain sulfur iron mine, with the indicators of the ore spontaneous combustion tendency as the interval number. It was found that the 30-day oxidation weight gain rate exerts the most significant influence on ore spontaneous combustion. The ore in ore layer no. 1 was prone to spontaneous combustion with relatively reliable results, while the ores in ore layers no. 2 and 3 were susceptible to self-heating with highly reliable results. This study provides a reference and guidance for the targeted prevention of ore spontaneous combustion in the mine. Full article

Background/Objectives: Emergency department (ED) visits for pediatric home accidents may provide an opportunity to identify children who warrant evaluation for attention-deficit/hyperactivity disorder (ADHD). This study primarily evaluated the feasibility of a two-step ED-based ADHD screening and Child and Adolescent Psychiatry referral pathway. A secondary exploratory objective was to compare the frequency of confirmed ADHD between children presenting with home accidents and non-injured ED controls. Methods: This prospective, two-center case-control study was conducted in two emergency departments in Denizli, Turkey, between October 2022 and June 2023. Children aged 5–11 years were enrolled as home-accident cases or non-injured controls. Parents or guardians completed the Turkish-validated Turgay DSM-IV Disruptive Behavior Disorders Rating Scale (DDDRS). Screen-positive children and those with prior documented ADHD were referred for DSM-5-based diagnostic confirmation or record verification by Child and Adolescent Psychiatry specialists blinded to group allocation. Feasibility outcomes included completion of ED screening, referral threshold positivity, and attendance at specialist assessment. Results: The study included 139 home-accident cases and 139 controls. Among 267 children eligible for ED screening, all completed the DDDRS. Forty-nine children (18.4%) met the referral threshold, and 40 of 49 (81.6%) attended the Child and Adolescent Psychiatry assessment. Overall, ADHD was confirmed in 21 cases (15.1%) and 9 controls (6.5%) (unadjusted odds ratio [OR], 2.57; 95% confidence interval [CI], 1.13–5.83; p = 0.020). In an exploratory multivariable logistic regression model adjusted for sex, age, and school grade, confirmed ADHD remained associated with home-accident case status (adjusted OR, 2.45; 95% CI, 1.06–5.65; p = 0.035). However, a sensitivity analysis restricted to children without prior treated ADHD showed a non-significant difference in newly diagnosed ADHD (12/130 vs. 7/137; OR, 1.89; 95% CI, 0.72–4.96; p = 0.190). Conclusions: A two-step ED screening and specialist referral pathway for ADHD after pediatric home-accident presentation was operationally feasible in this two-center sample. The higher overall frequency of confirmed ADHD among home-accident cases should be interpreted as a secondary exploratory finding because it was partly influenced by imbalance in pre-existing ADHD and was not confirmed in the newly diagnosed-only analysis. Larger studies with center-level data, broader confounder measurement, and longitudinal follow-up are needed. Full article

Background/Objectives: Opioid requirements among patients with spine trauma vary widely, yet the patient- and injury-level factors associated with high morphine milligram equivalent (MME) dosing at discharge remain unclear. This study aimed to characterize factors associated with high-dose MME at discharge. Methods: We conducted a retrospective cohort study of adult patients with spine trauma from 2019 to 2020. After excluding patients without spine trauma, 1593 patients with an opioid prescription at discharge were categorized into low-dose (below the cohort median MME) and high-dose (at or above the cohort median MME) groups. Patients in the high-dose group were propensity-score matched 1:3 to low-dose controls (with replacement) on age, sex, race, ethnicity, chronic opioid use, chronic pain syndrome, and other substance use. Within the matched cohort, a multivariable logistic regression model with cluster-robust standard errors was fitted to examine factors associated with high-dose MME (cutoff at 384). Covariates included spine trauma group (isolated vs. polytrauma, isolated as reference), injury severity score (ISS) stratum (ISS ≤ 15 as reference), head injury severity category, spine injury severity category, procedural status (non-surgical as reference), mechanical ventilation status (non-ventilated as reference), hospital length of stay, and discharge disposition (home/home health as reference, versus rehabilitation, nursing home, or other facility). Adjusted odds ratios (aORs) with 95% confidence intervals (CIs) were reported. Results: Of the 1593 patients included, 793 were in the low-dose MME group and 800 in the high-dose group. In the propensity-matched cohort, surgical procedures were associated with high-dose MME (aOR 1.52 [95% CI, 1.18–1.95]; p = 0.001). Discharge to inpatient rehabilitation (aOR 0.30 [95% CI, 0.14–0.64]; p = 0.002) and discharge to a nursing home (aOR 0.41 [95% CI, 0.30–0.56]; p < 0.001) were independently associated with lower odds of high-dose MME relative to home discharge. Spine trauma type, ISS stratum, head and spine injury severity category, mechanical ventilation, discharge to other facilities, and hospital length of stay were not associated with high-dose MME. Conclusions: This study demonstrates that discharge opioid prescribing in spine trauma is shaped more by procedural and discharge practices. These findings underscore the need for targeted opioid stewardship interventions at the points of surgical decision-making and discharge planning. Full article

Existing chaos-based image ciphers may suffer from limited dynamical complexity in low-dimensional maps and insufficient diversification of encryption-control sequences across different encryption instances. To address these limitations, a one-dimensional logarithmic chaotic map and a plaintext-dependent encryption scheme with dynamic DNA point mutation are presented. The map combines logarithmic stretching with modular folding and exhibits persistent complex dynamics over the investigated parameter interval. Compared with the logistic map and the one-dimensional Cosine Logistic compound map (1DCLC), it shows a broader positive-Lyapunov-exponent region and more stable normalized permutation entropy, while derived binary sequences satisfy the adopted NIST SP 800-22 criteria. The encryption architecture integrates block-reversal permutation, dynamic DNA encoding, involutive point mutation, and chaotic XOR masking. A SHA-512 plaintext digest, a fresh 128-bit public nonce, and a 256-bit master key are processed through HMAC-SHA-256 and HKDF-SHA-256 to derive the chaotic parameters. Experiments on standard grayscale images show near-uniform ciphertext distributions, negligible adjacent-pixel correlations, near-maximal entropy, differential characteristics close to theoretical references, and pronounced one-bit key sensitivity. The MATLAB implementation achieves encryption and decryption throughputs of approximately 1 MB/s. Full article

Received-signal-strength (RSS) visible light positioning (VLP) with a single photodiode (PD) usually assumes an upward-facing receiver. This convention simplifies the channel model, but it leaves receiver orientation unused even though orientation changes RSS sensitivity and LED visibility. We study a two-measurement localization cycle: an initial upward RSS vector gives a coarse position estimate, and we then orient the PD before acquiring a second vector. We use expected posterior localization mean-square error to motivate the sensing decision and develop two efficient local-information policies. Point scores the coarse estimate, whereas Stencil examines a nine-point neighborhood while enforcing LED visibility. After steering, we jointly fit the upward and steered RSS vectors for every policy. Using common Monte Carlo realizations and paired bootstrap intervals, we compare the policies with fixed upward reception, random steering, center pointing, and maximum-predicted-RSS steering. In 4-LED and 6-LED rooms, both local-information policies reduce RMSE by 18–20% relative to fixed upward reception; in an 8 m room, the reductions are about 40%. We further compare the selected actions with a finite grid-posterior reference and examine sensitivity to stencil parameters and actuator rotation error. The reference confirms that Point and Stencil are Bayes-risk-motivated surrogates, not exact Bayes optimizers. Full article

Background/Objectives: Cholesterol sulfate (CS) is a multifunctional signaling molecule implicated in diverse physiological and pathological processes. Its clinical translation as a biomarker is hindered by the lack of established reference intervals, unclear disease-specific alterations, and undefined relationships with routine laboratory parameters. This study aimed to establish a serum CS reference range for Chinese populations, evaluate its associations with various diseases and clinical laboratory parameters, and define its clinical diagnostic utility. Methods: A total of 642 subjects were enrolled, comprising 372 healthy controls and 270 patients with one of six diseases: Alzheimer’s disease, osteoporosis, obesity, type 2 diabetes mellitus (T2DM), non-alcoholic fatty liver disease (NAFLD), or Crohn’s disease. Serum CS concentrations were quantified using LC-MS/MS. Reference intervals were established using non-parametric methods. Univariate analyses included Spearman’s rank correlation, Mann–Whitney U test, and receiver operating characteristic (ROC) curve analysis; multivariate analysis employed a gamma-family generalized linear model (GLM) with a log-link function, incorporating age, sex, clinical laboratory parameters, and disease status as covariates. The age-by-sex interaction was examined to assess synergistic effects. Incremental diagnostic value of CS was evaluated using the DeLong test and likelihood ratio test. Results: The serum CS reference interval for healthy individuals was 0.55–2.24 mg/L (males: 0.60–2.25 mg/L; females: 0.54–2.20 mg/L), with a significant sex difference. The age-by-sex interaction effect was significant (two-way ANOVA interaction p = 0.005; GLM interaction β = 0.102, p = 0.002). Stratified analysis revealed a significant positive correlation between age and CS in males, but no such association in females. In univariate analysis, CS correlated significantly with total cholesterol (TC), non-HDL-C, hemoglobin A1c (HbA1c), and other biomarkers; CS levels were elevated in Alzheimer’s disease and reduced in Crohn’s disease. In the multivariate GLM, only TC and male sex emerged as independent significant determinants of CS, whereas HbA1c and NAFLD showed borderline effects; no disease group retained independent significance. After adjustment for TC and sex, the residual area under the curves (AUCs) of CS for all diseases were close to 0.50, and DeLong’s test indicated no incremental diagnostic value beyond the baseline model (all p > 0.70). Conclusions: This study is the first to establish a serum CS reference range for the Chinese population. Serum CS levels are independently regulated by TC and sex, with a significant age-by-sex interaction. The associations between CS and disease status were largely mediated by confounding from lipid profiles and age. CS is not suitable as an independent disease biomarker but may serve as a supplementary indicator for assessing lipid metabolism—particularly in male populations, where it may indirectly reflect age-related changes in cholesterol metabolism. Full article