PIFA PLUSS P4 Assay for Screening of Heparin-Induced Thrombocytopenia

Background The PIFA PLUSS PF4 Rapid Assay (PIFA) is a rapid screening test used for the diagnosis of heparin-induced thrombocytopenia (HIT). Objective To determine the usefulness of this assay as a screening method in our institution. Methods A total of 159 specimens from patients with suspected HIT were included in our study. We simultaneously performed PIFA assay and confirmatory polyspecific enzyme-linked immunosorbent assay (ELISA). We subjected most of the specimens with false-negative results to serotonin release assay (SRA). Results The initial sensitivity and specificity of the PIFA assay were calculated as 27.3% and 71.5%, respectively. A total of 12 of 16 false-negative results were further tested using the SRA method. The revised sensitivity and specificity were 50.0% and 73.5%, respectively. Conclusions Despite its appealing feature of yielding rapid results, the PIFA assay is inadequate as a sole screening test for HIT because of its high probability of missing many true cases of HIT.