ABSTRACT
Background: Prothrombin time (PT) and activated partial thromboplastin time (APTT) are the tests used in the investigation and monitoring of hemostatic disorders. Plasma is used to perform these tests immediately or stored for later use. The time and storage temperature have been shown to affect the results of these tests. Thus; all coagulation laboratories need guidelines for plasma storage to ensure reliable results. Objective: To determine the effect of varying storage times and temperatures on plasma PT and APTT. Materials and Methods: PT and APTT were run on plasma from 40 healthy adults using a semi-automated coagulometer. PT and APTT were measured at 0; 4; 6; and 24 h on samples stored at room temperature; refrigerated samples; and frozen samples. The values at 0 h were compared with the values at 4; 6; and 24 h. Results: PT and APTT values were within the reference ranges at 0 h. For refrigerated plasma; PT values at 4 h were within normal; but at 6 and 24 h; they were significantly deranged (P 0.05). PT was significantly different at 4; 6; and 24 h for both room temperature and frozen plasma (P 0.05). The APTT showed significant differences between 0 h value and values at 4; 6; and 24 h for all the varying temperature conditions. Conclusion: For reliable PT and APTT results; samples should be processed and run immediately after collection. However; plasma for PT can be stored at 2o-4oC for only 4 h