Influence of Preanalytical Variables on Prothrombin Time, Activated Partial Thromboplastin Time, and Fibrinogen

Background: In the present study, the influence of preanalytical variables on prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen testing is investigated. Methods: Samples collected from 104 patients were used for the study. PT, aPTT, and fibrinogen levels were tested with 50%-filled tubes to investigate the influence of sample volume. We measured the same parameters immediately after sampling, after 6 hours, and after 24 hours to investigate the influence of storage time. Samples were also tested after 6 hours at 4 degrees C to investigate the influence of storage temperature. Results: Use of 50%-filled tubes did not alter the results of PT and fibrinogen testing, but caused a significant bias to the aPTT test. The results of aPTT at 24 hours were also significantly different from results immediately after sampling. However, uncentrifuged citrated samples stored for 24 hours at room temperature may still be suitable for PT and fibrinogen testing. Incubation at 4 degrees C for up to 6 hours did not bias the results of PT, aPTT, or fibrinogen testing. Conclusions: Whilst aPTT is malleable to preanalytical variables, PT and fibrinogen showed stable results across variations in sample volume, storage time, and temperature.