Impact of icterus on PT and APTT measured with photometric versus mechanical clot detection

Abstract Objectives Icteric plasma samples, common in liver diseases, may interfere with photometric clot detection. This study was aimed to compare prothrombin time (PT) and activated partial thrompoblastin time (APTT) from non-icteric and icteric plasma samples using Werfen ACL TOP 750 and Stago sthemO 301. Methods We analyzed 100 routine plasma samples (50 icteric, 50 non-icteric) for PT and APTT using ACL TOP 750 (photometric clot detection) and sthemO 301 (mechanical clot detection). PT and APTT were measured in duplicate, and the icteric index (I-index) was recorded. Inter-analyzer agreement was assessed with correlation analysis, linear fit, bootstrap analysis and hypothesis testing for equality of regression slopes and intercepts. Results Non-icteric samples had a mean I-index of 1.0 ± 0.0 vs. 2.4 ± 0.7 in icteric samples (p