Fibrinogen assays are an important screening tool for blood coagulation disorders. Although different methods are available, no consensus has been reached as to which method is preferable. In 27 patients with dysfibrinogenemia, plasma fibrinogen concentration was measured by Clauss and PT-derived methods on two fully automated coagulation analyzers utilizing different reagents. In addition, immunological and heat fibrinogen concentrations as well as global coagulation tests were measured.
Results: The median fibrinogen determined by the Clauss assay was 0.40 g/l, with a range of 0.30-2.07 g/l (normal range: 2.67-4.37 g/l) and 0.60 g/l, with a range of 0.60-2.20 g/l (normal range: 1.5-4.5 g/l) using two different reagents. The median fibrinogen determined by the PT-derived method was 2.41 g/l, with a range of 0.97-4.87 g/l (normal range: 1.84-4.8 g/l) and 2.64 g/l, ranging from 1.38 to 4.39 g/l (normal range: 2.0-4.0 g/l) by the use of two different reagents. No correlation was found when comparing both methods using two reagents from different manufacturers. The PT-derived method "overestimated" the fibrinogen by approximately five times the value measured by the Clauss assay. While fibrinogen measured by the PT-derived method correlated with fibrinogen antigen concentrations measured by the immunological fibrinogen (p<0.002) or heat fibrinogen method (p<0.002), fibrinogen measured by the Clauss method correlated with functional coagulation parameters, such as Reptilase Time (p<0.002), Thrombin Time (p<0.002) or Prothrombin Time (p<0.02).
Conclusion: Although many patients with dysfibinogenemia are asymptomatic, in case of bleeding, immediately diagnosis and treatment is warranted. The Clauss assay is the diagnostic tool of choice when diagnosing or treating patients with low fibrinogen levels. The use of the PT-derived method may potentially pose a greater risk to patients, as the plasma concentration may be erroneously reported as normal.
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