Fibrinogen estimates are influenced by methods of measurement and hemodilution with colloid plasma expanders

BACKGROUND: Measurement of plasma fibrinogen is often required in critically ill patients or massively bleeding patients being resuscitated with colloid plasma expander. This study aimed at evaluating different assays of plasma fibrinogen after in vitro dilution with commonly used plasma expanders and challenged the hypothesis that levels of fibrinogen are estimated significantly higher in plasma diluted with colloid plasma expander compared with isotonic saline. STUDY DESIGN AND METHODS: Fibrinogen measurements were established in plasma samples each diluted in vitro to 30 or 50% with isotonic saline, hydroxyethyl starch (HES) 130/0.4, and human albumin. Fibrinogen levels were assessed using an antigen determination, three photo-optical Clauss methods, one mechanical Clauss method, a prothrombin-derived method, and viscoelastic measurement through thromboelastometry. RESULTS: Measurement of fibrinogen levels was significantly different when performed on alternate analytical platforms. By 30 and 50% dilution with HES 130/0.4 coagulation analyzers using the photo-optical Clauss methods significantly overestimated levels of fibrinogen. Dilution with human albumin did not affect fibrinogen levels except from one analyzer by 50% dilution level. Viscoelastic measurement of fibrin polymerization was reduced at both dilution levels and appeared to reflect the impairment of fibrin polymerization induced by HES 130/0.4 and to a lesser extent human albumin. CONCLUSION: This study demonstrated that different automated coagulation analyzers revealed significantly different levels of fibrinogen. The presence of colloid plasma expander gave rise to erroneous high levels of fibrinogen returned from some coagulation analyzers employing the method of Clauss.