Rapid laboratory identification of fibrinogen Longmont: a case report and literature review

This case describes a patient with unstable angina who had abnormally low fibrinogen levels detected during preoperative screening, yet clinical manifestations were inconsistent with test results. Comparative analysis of multiple laboratory methods revealed that the optical fibrinogen assay produced falsely low results (below 0.35 g/L), while the magnetic bead assay showed normal values (4.18 g/L; reference range 2–4 g/L). Genetic testing ultimately confirmed a rare dysfibrinogenemia—fibrinogen Longmont. This rare fibrinogen variant can cause discrepancies depending on the assay method, reagent system, and algorithm used. The study emphasizes the importance of proper interpretation of coagulation tests to prevent misdiagnosis and inappropriate treatment.