Sample preparation for plasma measurement of plasminogen activator inhibitor-1 antigen in large population studies.

Plasminogen activator inhibitor-1 is important in regulating fibrinolysis and may be an important cardiovascular risk factor. Because of this, there is increased interest in performing plasminogen activator inhibitor-1 assays in large epidemiologic studies. Our aim in this study was to determine the simplest blood collection methods that yield accurate results with our plasminogen activator inhibitor-1 antigen assay. Our results indicate that the following issues are important: (1) since there is a large circadian variation in plasminogen activator inhibitor-1 plasma levels, a target time frame must be established; (2) commercially available citrate collection tubes are adequate, if sample processing is rapid; (3) careful venipuncture is necessary, with freely flowing collection; hemolysis must be avoided; and (4) centrifugation of at least 30,000 g.min is required to avoid platelet contamination.