[Comparison of heparin-induced prolongation of APTT in 12 different laboratories in Kyushu area].

APTT is widely used for serial monitoring of treatment with unfractionated heparin. However, since its sensitivity to heparin varies significantly from one reagent to another, it is suggested that the therapeutic range had to be defined for each brand of APTT reagents. In this study, to investigate the affect of these variables, we compared various reagents of APTT and instruments for APTT measurements in different laboratories of university hospitals and related hospitals in Kyushu area. Same sample of normal pooled plasma added unfractionated heparin were measured in each laboratory. Prolongation of APTT by unfractionated heparin differed between laboratories. In addition, we examined prolongation of APTT by unfractionated heparin in normal plasma obtained from single donor. The prolongation of APTT differed between single donor samples even in the using of single APTT reagent and instrument. No correlation was observed between prolongation ratio of APTT and antithrombin concentration. These results indicate that sensitivity to heparin varies between individual in addition to brand of APTT reagent.