The influence of time, temperature and packed cell on activated partial thromboplastin time and prothrombin time

Activated partial thromboplastin time (APTT) and prothrombin time (PT) were performed in four groups of studies in order to evaluate the influences of time, temperature, and different forms of plasma storage to the result. Different designs for storage of the plasmas were studied, including the plasmas stored either with or without packed cells, the plasmas stored in the cuvette with exact volume for performing the test or in the test tube. The temperatures for store of the plasma were at room temperature, at 4 degrees C and at -70 degrees C. The time for store of the plasma was from 1 hour up to 7 hours. The plasmas included normal pooled plasmas and diseased plasmas. From this study, it is found that the PT test was not easily affected by the temperature, storage time and the form of storage in comparison with the APTT test which was much easily affected by the above conditions. APTT should be done within 2 hours after sampling and the plasma should be stored with the packed cells at 4 degrees C in order to obtain a reliable result. PT could be done within 7 hours without influence to the result if the plasma was stored with the packed cells at 4 degrees C. No significant cold-induced shortening of PT could be noted when the plasma was incubated at 4 degrees C up to 7 hours. In either PT or APTT, the most suitable condition for storing the plasma should be with the packed cells at 4 degrees C.