Longitudinal stability of coagulation, fibrinolysis, and inflammation factors in stored plasma samples

We sought to assess the longitudinal stability of risk factors for atherosclerosis and thrombosis. including several coagulation, fibrinolysis, and inflammation factors, in frozen plasma samples stored at -70 degrees C for months or years. We reviewed data collected on 29 different control pools over periods ranging from 7 to 59 months for two functional assays (factor VII and fibrinogen) and seven antigen measurements (C-reactive protein, D-dimer, plasmin-alpha (2)-antiplasmin complex, plasminogen activator inhibitor-1, protein C. protein S, and tissue plasminogen activator), totaling more than 15,000 data points. Screening of the data using least squares regression revealed only sporadic associations between monthly means and time. with no consistent trends. Analysis by repeated measures and summary measure methods revealed no evidence of sample degradation over time for the factors studied. Our finding of longitudinal stability in the biochemical properties of frozen plasma strengthens the presumption of sample stability on which molecular epidemiologic studies are based.