Summary
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° 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-α 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.
Keywords Acute-phase proteins - atherosclerosis - blood coagulation factors - molecular epidemiology
- thrombosis