Influence of time, temperature, and mechanical agitation on whole-blood and plasma sample stability in coagulation tests.

Preanalytical variables strongly influence coagulation test results; however, their combined effects remain insufficiently evaluated. This study examined whole-blood and plasma stability under conditions mimicking current sample storage and transport practices, focusing on three variables: time, temperature, and mechanical agitation. Coagulation tests were performed using four manufacturers' systems, and sample stability was assessed using percentage changes with a 10% criterion and statistical analysis. Among all conditions tested, frozen plasma was consistently the most stable across assays. Whole blood stored at room temperature showed relatively smaller changes, whereas refrigerated whole blood exhibited the largest variation, with factor VIII activity and von Willebrand factor antigen levels decreasing to ≤ 30% even in samples obtained from healthy participants. In some refrigerated samples, clotting times shortened, leading to false-negative lupus anticoagulant results. Mechanical agitation had only marginal effects compared with time and temperature. Sample stability differed substantially between whole blood and plasma and across test types, and the alteration of sample quality accelerated depending on time and temperature conditions, leading to variable testing results. This study underscores the importance of immediate frozen plasma preparation after blood collection to prevent misinterpretation in clinical practice, particularly when prolonged storage is unavoidable, as in outsourced testing.