Abstract

THE EFFECT OF THROMBOPLASTIN REAGENTS WITH DIFFERENT TYPES (LYOPHILIZED VS. LIQUID) ON THE INTERNATIONAL NORMALIZED RATIO (INR)

Ghassan A. Khaleel , Khalid A. Mahmood and *Meroj A. Jasem

Abstract

Introduction: Prothrombin time (PT) is a commonly used in vitro laboratory test to investigate the extrinsic and common pathway of coagulation. The primary use of PT is for monitoring warfarin therapy. Different ways of reporting the results were used and the International Normalized Ratio (INR) was devised to standardize PT reporting in long-term anticoagulant users. Aim of the study: To evaluate the effect of thromboplastin reagents with different types (lyophilized Vs liquid), on the International Normalized Ratio (INR) results .Patients and methods: This prospective case-control study involved 125 patients already on warfarin therapy for more than one week attending the Coagulation Unit in the Teaching Laboratories of Baghdad Medical City. A group of 33 apparently healthy individuals who had not taken any medication in the last 5 days were included as controls. PT was preformed to all patients using thromboplastin reagents with different types (lyophilized Vs liquid). Results: Comparison between different types of thromboplastin reagents (lyophilized and liquid) showed significant difference in group 2 & 3 (p = 0.029) and (p = 0.005) respectively. , the mean Prothrombin time by low International Sensitivity Index reagent was significantly longer from that using high International Sensitivity Index reagent both lyophilized and the liquid form in both the second and third group however the difference was minimized on converting the results into International Normalized Ratio with the lyophilized thromboplastin while persist for the liquid form.Conclusions: In patients with normal PT there is no need to convert it into PTR and INR. In patients with prolonged PT the disparities of the results using different types (lyophilized Vs liquid) reagents were found. Liquid thromboplastin gave PTs which were significantly different from that obtained by lyophilized which maintained even on expression of the results as PTR or INR.

Keywords: Thromboplastin reagents, Prothrompin Time, International Normalized Ratio (INR).