Specific reference intervals (RIs) facilitate accurate interpretation of results. Coagulation assay results may vary by demographics and also between reagents and analyzers used. Current Thromboelastograph 6s (TEG 6s) Hemostasis Analyzer RIs were generated from adult samples.


To generate reagent analyzer-specific pediatric RIs for TEG 6s and coagulation parameters.


A prospective, observational, single-center study of healthy children undergoing general anesthesia (January 3, 2017 to January 3, 2019). Venous blood samples were obtained for TEG 6s (Kaolin, Kaolin-Heparinase, Rapid and Functional Fibrinogen assays) and coagulation parameters (activated partial thromboplastin time, prothrombin time, thrombin clotting time, Echis time, antithrombin activity, and fibrinogen concentration using Instrumentation Laboratory ACL-TOP analyzers). Differences between activated partial thromboplastin time and prothrombin time reagents were investigated using mixed-effects regression, comparing maximum coefficients-of-variation with assay-specific allowable variation. RIs (lower/upper limits 2.5th of 97.5th percentiles) were generated using the following 2 methods: within discrete age-groups (neonates [<1 month], infants [1 month–1 year], young children [1–5 years], older children [6–10 years], and adolescents [11–16 years]), and modeled as functions of age and/or sex using quantile regression, including significant fractional polynomial and interaction terms.


Variation between prothrombin time and activated partial thromboplastin time assays using different reagents was clinically significant. Reagent-analyzer specific pediatric RIs were generated using data from 254 children. Discrete and model-based RIs varied by age for all coagulation parameters and TEG 6s variables in all assays.


We report reagent-analyzer specific pediatric RIs for TEG 6s and coagulation parameters. Observed variation reinforces recommendations for laboratory-specific RIs. These findings improve accuracy of interpretation of clinical results, provide a foundation for comparison and validation of tests in pathology and illustrate feasibility and advantages of model-based RI approaches.

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Competing Interests

The authors have no relevant financial interest in the products or companies described in this article.

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Gibbons and Roy contributed equally as senior authors.

Supplementary data