Improving equivalence in fibrinogen evaluation between the prothrombin time-derived fibrinogen assay and Clauss method using a pooled plasma calibrator.

Aims: Both the Clauss and prothrombin time-derived fibrinogen (PT-Fib) methods have widely been used in fibrinogen (Fib) evaluation. We aimed to improve the interchangeability between these two methods.

Methods: Thirty fresh plasmas of low, normal and high Fib concentration were mixed to prepare the pooled human plasma. The Fib concentration was assessed by the Clauss method. The PT-Fib values were further recalibrated by the assigned plasma pools and the precision, linearity and reference intervals were verified according to the guidelines of American Society for Clinical and Laboratory Standards (CLSI) EP15-A and EP6-A documents. Finally, the recalibrated PT-Fib method was compared with Clauss method by the simultaneous Fib test of total 5259 coagulation samples.

Results: The results indicated that the recalibrated PT-Fib method can detect the Fib concentration with clinically acceptable third-order linearity in the range of 1.27-8.00 g/L. Only one result out of 39 healthy people tested using the recalibrated PT-Fib method did not fall within the reference range defined by the manufacturer. We also found more than 99% of results between these two methods were interchangeable in the range of 1.51-8.00 g/L. The disagreement between these two methods was found only in patients with certain underlying conditions.

Conclusions: After recalibration, the consistency between the PT-Fib and Clauss methods was enhanced and the interchangeability was improved. The application of the recalibrated PT-Fib method provided accurate and reliable results with the manufacturer-provided reagents and improved detection speed and cost-effectiveness.