Comparison of two coagulometers for the determination of activated partial thromboplastin time, prothrombin time and thrombin time

Activate d partia l thromboplasti n tim e ( APTT) , prothrombi n tim e ( PT ) and thrombin time (TT) are useful tests for detecting abnormality of coagulation factor s involve d i n coagulatio n cascad e an d mornitorin g anticoagulan t levels . Th e ai m o f thi s stud y wa s t o compar e tw o electric-mechanica l coagulometer s i n ou r laboratory , KC4 A (Amelung , Germany ) an d ST 4 BI O (Diagnostic a Stago) , whethe r th e instrument s woul d giv e differen t APTT , P T an d T T results . Th e stud y wa s performe d i n 10 0 patients’sample s sen t t o th e Hematologica l Division, Department of Pathology, Faculty of Medicine, Ramathibodi Hospital for coagulation study. Normal control plasma was also analyzed for precision study. The results demonstrated that the mean values of APTT, PT and TT performed by the two instrument s i n norma l contro l plasm a wer e similar . Rang e o f Coe ff icien t o f variatio n (CV ) o f within-ru n precisio n wa s 1.29%-2.23 % an d tha t o f between-ru n precisio n wa s 1.8%-5.04% . Th e compariso n stud y usin g 10 0 patients ’ sample s indicate d correlatio n betwee n the instruments and r values were 0.994, 0.996 and 0.992 for APTT, PT and TT, respectively ( p <0.001), revealing linear regression curves ( p <0.0001). There were no significant differences of the mean values of APTT ( p =0.43), PT ( p =0.29) and TT ( p =0.40). In conclusion, both KC4A and ST4 BIO coagulometers gave high result preci- sion and there is no differences in the determination of APTT, PT and TT especially for mornitoring of anticoagulants. Thus, we can use one as a substitution for the other.