A-347 Statistical determination of infant (<6 months) PT and PTT reference intervals

Abstract Background Normal Prothrombin Time (PT) and activated partial thromboplastin time (aPTT) values fluctuate in infants <6 months of age due to developmental hemostasis. Because of early alterations in vitamin K levels, PT and aPTT levels that are abnormal in adults could be within the expected range for an infant. PT and aPTT are not harmonized, results can vary among manufacturer platforms, thus instrument specific reference intervals are needed. The objective of this study was to establish reference intervals in infants for PT and aPTT on the Werfen ACL-TOP platform. Methods Results were established using the ACL-TOP instrument with Werfen reagents. Using the electronic medical records, historical patient results were evaluated using ± 2SD to determine a reference interval. Inclusion criteria included age <6 months with available coagulation testing. Exclusion included anticoagulation, congenital heart disease and significant systemic illness. Patient results were sorted by age at time of collection (<6 months) and by year to establish a range for Children’s Hospital of Philadelphia for each year starting in 2021. One hundred patient results were included per year for a total n of 400. All of the data was then combined to establish a total range from 2021-2024 and compared to available reference intervals in the published literature.1-3 Results See attached Jpeg Conclusion Infant reference intervals for the central 95% of the population were determined to be 8.9-16.1 seconds for PT and 24.6-50.1 seconds for aPTT from the years 2021-2024 using historical CHOP data. These data were comparable to data by other instrumentation in other published literature.1-3