Effect of pre-analytical variables on coagulation tests in hepatitis B patients.

To determine the effects of various pre-analytical variables on the values of activated partial thromboplastin time (APTT), D-dimers, fibrinogen (Fbg), prothrombin time (PT) and thrombin time (TT). Samples from 120 hepatitis B patients were divided into three groups based on storage time (0-24 h), mechanical agitation and separation into plasma. In all groups, samples were stored at room temperature and 4°C. The percentage changes compared to the baseline were calculated. Clinically relevant differences were defined as a more than 10% change. If less than 25% samples showed relevant differences, the effect of the pre-analytical variable was considered moderate; if more than 25% of samples showed relevant differences, the effect was deemed large. Clinically relevant differences in APTT were found in separated samples stored for 24 h. No relevant differences were seen in the other test results. All tested pre-analytical variables had a moderate effect on the D-dimer, Fbg, PT and TT values. Storage for 24 h had a large effect on APTT. Coagulation test results were unaffected by temperature, storage time, mechanical agitation and sample separation. Specimens for D-dimer, Fbg, PT and TT tests could be stored for 24 h, and specimens for APTT could be stored for 8 h.