# Diagnostic Performance of Prothrombin Time and Activated Partial Thromboplastin Time in Children: A Service Evaluation

## TL;DR

This study evaluates how often and how effectively prothrombin time and activated partial thromboplastin time tests are used in children to detect bleeding disorders.

## Contribution

The study identifies a specific APTT threshold for detecting inherited bleeding disorders in children.

## Key findings

- 15.7% of coagulation tests were rejected due to sample issues.
- 28.8% of randomly selected patients had clinically significant abnormal results.
- An APTT > 31.4 seconds was strongly associated with inherited bleeding disorders.

## Abstract

Coagulation screening, consisting of prothrombin time (PT) and activated partial prothrombin time (aPTT), is routinely performed in paediatrics to identify bleeding disorders or guide peri‐procedural management. We evaluated the trends in utilisation and diagnostic yield of PT and aPTT testing as part of coagulation screening in a tertiary paediatric centre.

All PT and aPTT samples received from June to September 2024 were analysed. Total requests, sample rejection rates, abnormal result patterns (isolated PT, isolated APTT, combined), and clinical correlations were recorded. Laboratory cutoffs were PT > 12.5 s and APTT > 30.0 s. Youden's Index determined cutoffs associated with inherited bleeding disorders.

A total of 2808 coagulation profiles from 1207 patients were received, with 15.7% (442/2808) rejected in 268 patients. Of these, 31.7% (85/268) of patients were not re‐tested. Among valid requests, 17.0% (402/2366) were abnormal (128 isolated APTT, 173 isolated PT, 101 combined). In a subgroup of 337 randomly selected patients, 28.8% (97/337) had deranged results, leading to 12 new haematological and 34 acute diagnoses. Youden's index determined isolated APTT > 31.4 s associated with inherited disorders (AUC > 0.8). The same was not identified with isolated PT (PT > 13.0 s, AUC < 0.6).

A substantial proportion of samples received are rejected, and some abnormal results remain unaddressed. Most abnormal findings are clinically significant, particularly when APTT > 33.1 s. There is scope to refine utilisation in paediatric practice.