Validation of Pre-analytical Stability of Specimens Requested for Various Routine Coagulation Tests

Abstract

Purpose: This study aimed to investigate the reliability of coagulation tests after storage of centrifuged samples in the primary collection tube with plasma remaining on top of the cells at room temperature and to compare results with current CLSI guidelines and previous studies. Methods: Surplus blood samples from 20 patients were stored in the primary collection tube at room temperature, and were tested 2, 4, 6, 8, 12, 24, and 48 hr after the initial testing. The tests included aPTT/ PT/fibrinogen/D-dimer, coagulation factors (F) VIII/IX/XI/XII/II/V/VII/X, von Willebrand factor (vWF) antigen and activity, antithrombin III (ATIII), fibrinogen degradation product (FDP), and dilute Russell’s viper venom time (dRVVT) screening and confirmation. A clinically significant difference was determined by a percentage change of > 10% according to the 99% confidence interval. Results: Storage of the sample in aPTT/PT/FVIII/FIX/FXI/FXII/FII/FV/FVII/FX/dRVVT screening and confirmation provided acceptable results up to 12/24/2/12/6/4/6/2/8/6/12, and 24 hr, respectively. For fibrinogen/ D-dimers/vWF antigen and activity/ATIII/FDP, storage up to 48 hr also provided acceptable results. Compared to CLSI guidelines, the same acceptable storage periods for PT/FXII, shorter periods for FVIII/FV, and longer periods for the others tests were identified. Compared to previous studies that stored plasma after aliquotation, the acceptable storage periods were generally shorter for the coagulation factor assays. Conclusion: The recommendations from the CLSI guidelines are too stringent in general but more strict storage limits should be applied to FVIII/FV. When additional coagulation factor assays are ordered and additional sample acquisition or preparation is not possible, more strict acceptable storage time criteria would be needed.