Fibrinogen testing : how, why and what are the limitations?

Fibrinogen testing is essential in the diagnosis and management of various bleeding and thrombotic disorders, as fibrinogen plays a central role in the coagulation cascade. This testing typically involves the assessment of both fibrinogen antigen levels and functional activity, with different methods used for each. The Clauss method, the most widely used test to measure fibrinogen activity, is based on clotting time following the addition of a high concentration of thrombin, providing a direct measure of functional fibrinogen. Alternatively, prothrombin time (PT)-derived methods estimate fibrinogen activity based on changes in the PT curve; although more indirect and subject to analytical variability, this can be useful in certain automated or resource-limited settings. Fibrinogen antigen levels are commonly measured using immunoassays, which quantify fibrinogen concentration in plasma. Gravimetric methods, though rarely used today, can also determine fibrinogen content based on the weight of the clot formed.

Despite its clinical relevance, fibrinogen testing presents several limitations, including inter-method variability, possible interference from other plasma components, and difficulty in distinguishing between pathological and transient fluctuations. Recognizing these limitations is crucial for clinicians to interpret results appropriately and guide treatment, especially in acute and critical care contexts. Therefore, while fibrinogen testing remains a cornerstone in hemostasis evaluation, it requires careful interpretation on a case-by-case basis for each patient.

The clinical utility of fibrinogen testing extends to various pathophysiological conditions, particularly in critical settings such as disseminated intravascular coagulation (DIC) and postpartum hemorrhage (PPH), where fibrinogen levels may drop dramatically. Identifying critical fibrinogen thresholds is key for clinical decisionmaking, as both hypofibrinogenemia and hyperfibrinogenemia are associated with increased morbidity and mortality. Measurement of fibrinogen activity and antigen also allows identification of dysfibrinogenemia, another condition possibly associated with pathological manifestations.
During this webinar, clinicians, clinical pathologists, PhDs, and clinical laboratory staff will have the opportunity to update their knowledge on fibrinogen testing — including how it is performed, why it is important, and what its limitations are.