Factor XIII – an under diagnosed deficiency – are we using the right assays?

Background: The clot solubility test is the most widely used method for detection of factor (F)XIII deficiency. However, it will only detect severe deficiencies; consequently mild deficiencies and heterozygous states are probably under diagnosed. Objective: As an alternative first‐line screening test, we assessed an automated quantitative ammonia release assay (QARA). Patients/methods: Inter‐assay imprecision was evaluated with commercial normal and pathological control plasmas (10 replicates on each of 5 days). Using the QARA and other commercial assays a comparative assessment of congenital (FXIII range