Investigation of Prothrombin Time, International Normalized Ratio and Activated Partial Thromboplastin Time reference ranges in children

INTRODUCTION: This study aimed to ascertain pediatric age-specific reference ranges for prothrombin time (PT), international normalized ratio (INR), and activated partial thromboplastin time (aPTT). Retrospective data were obtained from healthy children who had undergone preoperative tests and compared with those obtained from a group of adult patients.
METHODS: Reference individuals were determined by the indirect method. A total of 15,179 patients who presented to our hospital in 2022 and 2023 were retrospectively reviewed. Pediatric patients were divided into three age groups: 1–5 years (n=1949), 6–10 years (n=1563), and 11–17 years (n=508). The adult age group consisted of healthy individuals aged 18–50 years (n=11165). The tests were run in a coagulation autoanalyzer with the mechanical coagulometric measurement method. Reference ranges were analyzed using the non-parametric method statistically.
RESULTS: The mean PT, INR, and aPTT values were found to be 14.34±1.99 s, 1.07±0.16, and 31.43±3.47 s, respectively, in children aged 1–5 years; 14.48±1.40 s, 1.08±0.11, and 31.30±2.66 s, respectively, in those aged 6–10 years; and 14.73±1.12 s, 1.10±0.09, and 31.21±2.91 s, respectively, in those aged 11–17 years. Among the adults aged 18–50 years, the mean PT, INR, and aPTT values were 13.95±1.40 s, 1.04±0.11, and 30.21±2.86 s, respectively. The mean PT, INR, and aPTT values of children aged 1–5 years, 6–10 years, and 11–17 years were statistically significantly higher than those of adults aged 18–50 years (for each group p<0.01).
DISCUSSION AND CONCLUSION: It is important for laboratories to employ age-specific reference ranges for coagulation tests performed on children to ensure accurate diagnosis and avoid unnecessary further investigations. In this study, the reference ranges of the PT, INR, and aPTT parameters were determined for pediatric patients and found to be significantly higher than those of adults, which will be useful for clinical evaluation and diagnosis.