Distinguishing between quantitative and qualitative fibrinogen disorders entails measuring the discrepancy between fibrinogen antigen (Ag) and functional fibrinogen (Ac) levels. The Clauss fibrinogen assay, a widely used screening tool for fibrinogen disorders, measures only Ac and is therefore unable to classify fibrinogen disorders. Furthermore, measuring fibrinogen Ag can be difficult in nonspecialized laboratories.
In a report published in Thrombosis Research, a team of researchers suggested that clot waveform analysis, which uses optical methods to analyze coagulation, of the Clauss fibrinogen assay may provide an alternate method for fibrinogen disorder classification that does not require measuring fibrinogen Ag levels.
The researchers determined Ac levels, plasma fibrinogen Ag levels, and maximum coagulation velocity (Min1) for 91 normal patients and 27 patients with fibrinogen disorders. Of the patients with fibrinogen disorders, 15 had hypofibrinogenemia, 6 had dysfibrinogenemia, and 6 had hypodysfibrinogenemia. A nonlinear regression curve was used to calculate estimated fibrinogen Ag (eAg) levels from each Min1 value.
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Min1 values were found to be highly correlated with fibrinogen Ag levels (respective correlation coefficient = 0.9355) and yielded accurate eAg calculations regardless of sample quality.
The Ac/Min1 ratios in patients with hypofibrinogenemia and hypodysfibrinogenemia were significantly higher than the Ac/Min1 ratios in normal patients and patients with dysfibrinogenemia (P <.0001), indicating that Ac/Min1 ratios can be used to differentiate hypofibrinogenemia and hypodysfibrinogenemia from dysfibrinogenemia.
Of note, although Ac/Min1 ratios did not correlate with Ac/Ag ratios, Ac/eAg ratios were found to correlate with Ac/Ag ratios (P <.0001), suggesting that measuring eAg may be a suitable alternative to measuring fibrinogen Ag in order to distinguish between qualitative and quantitative fibrinogen disorders.
The authors concluded that combining measures of Ac/Min1 and Ac/eAg levels allows for classification of qualitative and quantitative fibrinogen disorders in nonspecialized and small laboratories, though they cautioned that they “could not clearly define a cutoff value of the Ac/eAg ratio to distinguish fibrinogen abnormalities because of small sample numbers.”
Reference
1. Suzuki A, Suzuki N, Kanematsu T, et al. Clot waveform analysis in Clauss fibrinogen assay contributes to classification of fibrinogen disorders [published online December 18, 2018]. Thromb Res. doi: 10.1016/j.thromres.2018.12.018
