Purpose: The aim of this study is to determine the activated partial thromboplastin time (aPTT), prothrombin time (PT), international normalized ratio (INR) reference values to be used in our hospital population.

Materials and methods: In this study, the data of preoperative aPTT, PT and INR levels of 279 healthy individuals aged 18-65 years in Konya City Hospital were evaluated. PT and aPTT parameters analyzed by the optical reaction method in Sysmex CS 2500 autoanalyzer. Reference intervals were calculated using the “R (The R Foundation for Statistical Computing) version 4.0.5 program.

Results: As a result of our study, based on the necessity of laboratories to determine reference intervals suitable for their own population, the reference interval was found to be 19.1-28.9s for aPTT, 10-13.7s for PT and 0.9-1.27 for INR.

Conclusion: The reference values we found in our study differ minimally from the values recommended by the manufacturer, we think that these values better reflect our patient population.