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The reference intervals of PT, INR and APTT tests on the Cobas analyzer in Turkish pediatric population

Berrak Guven1, Ismail Benice1, Bilgehan Acikgoz2

  • 1Department of Biochemistry, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey.

Scandinavian Journal of Clinical and Laboratory Investigation
|January 8, 2026
PubMed

Insights

This study established pediatric reference intervals for prothrombin time (PT), international normalized ratio (INR), and activated partial thromboplastin time (APTT) in Turkey. Age-stratified results using the Cobas t511 analyzer aid accurate pediatric coagulation diagnostics.

Area of Science:

  • Clinical Biochemistry
  • Pediatric Hematology

Background:

  • Accurate coagulation test reference intervals (RIs) are crucial for pediatric diagnostics.
  • Existing RIs may not be suitable for diverse pediatric populations or specific analytical platforms.

Purpose of the Study:

  • To establish pediatric-specific reference intervals (RIs) for prothrombin time (PT), international normalized ratio (INR), and activated partial thromboplastin time (APTT).
  • To utilize the Cobas t511 analyzer for reliable coagulation testing in a Turkish pediatric cohort.
  • To provide age-stratified RIs to enhance diagnostic accuracy.

Main Methods:

  • Retrospective analysis of preoperative laboratory results from 1065 healthy Turkish pediatric patients (0-18 years).
  • Application of Clinical and Laboratory Standards Institute (CLSI) guidelines for RI determination.
  • Nonparametric approach to define 2.5th-97.5th percentile reference limits.

Main Results:

  • Median (95% RI) values: PT 9.0s [8.1-10.5], INR 1.02 [0.93-1.17], APTT 29.7s [24.3-35.2].
  • Statistically significant age-related differences observed for PT, INR, and APTT (p < 0.001).
  • Data successfully stratified into 18 distinct pediatric age groups.

Conclusions:

  • The study provides the first pediatric-specific RIs for PT, INR, and APTT using the Cobas t511 analyzer in a Turkish population.
  • Age-stratified RIs improve the interpretation of coagulation tests in pediatric clinical practice.
  • These findings contribute to more accurate and reliable pediatric diagnostics.

Keywords:
Reference intervalactivated partial thromboplastin timecoagulation analyzerpediatricsprothrombin time

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