Purpose: The maturation of hemostatic system continues from fetal life to adult. Determination of agedependent reference ranges for coagulation is therefore very important to evaluate correctly the hemostasis. The study aimed to establish age-dependent reference range for prothrombin time (PT) and activated partial thromboplastin time (aPTT) as well compare pediatric and adult reference ranges.

Materials and Methods: Pediatric and adult patients who were requested PT and aPTT tests for the preoperative evaluation before minor elective surgery were enrolled in the study. Patients were separated into four groups (Group 1: 1-5 years old; Group 2: 6-10 years old; Group 3: 11-16 years old and Group 4: ≥18 years old). PT and aPTT were measured on SF8100 (Beijing Succeeder, China) coagulation analyzer by mechanic coagulometric method. Reagents were same brand with the coagulation analyzer. Reference ranges were determined by the non-parametric method or Robust method according to the sample size of groups. The z test was used to compare pediatric and adult reference ranges.

Results: 473 pediatric [Group 1 (n=120), Group 2 (n=324) and Group 3 (n=29)] and 143 adult patients were included into the study. The reference ranges for PT determined in pediatric groups were found to be similar to those of adult (calculated z value < critical z value). aPTT reference ranges were significantly higher in pediatric groups than that of adult group (calculated z value > critical z value).

Conclusion: aPTT reference range determined in pediatric population was longer time than that of adult population. Therefore, to prevent falsely abnormal classifications, the age-specific reference ranges should be used during evaluating aPTT results in the pediatric population.