Diagnostic accuracy of rapid immunoassays for heparin-induced thrombocytopenia A systematic review and meta-analysis

The platelet factor 4/heparin ELISA has limited specificity for heparin induced thrombocytopenia (HIT) and frequently does not provide same-day results. Rapid immunoassays (Rls) have been developed which provide results in 30 minutes or less. We conducted a systematic review and meta-analysis to evaluate the diagnostic accuracy of Rls for HIT. We searched the literature for studies in which samples from patients with suspected HIT were tested using a RI and a functional assay against which the performance of the RI could be measured. We performed sensitivity analyses of studies that directly compared different Rls with each other and with ELISAs. Estimates of sensitivity and specificity for each RI were calculated. Twenty-three articles, collectively involving six different Rls, met eligibility criteria. All Rls exhibited high sensitivity (0.96 to 1.00); there was wider variability in specificity (0.68 to 0.94). Specificity of the IgG-specific chemiluminascent assay (IgG-CA) was greater than the polyspecific chemiluminescent assay [0.94 (95 %CI 0.89-0.99) vs 0.82 (0.77-0.87)]. The particle gel immunoassay demonstrated greater specificity than the poly specific ELISA [0.96 (0.95-0.97) vs 0.91 (0.89-0.92)]. The IgG-CA and lateral flow immunoassay [0.94 (0.91-0.97)] exhibited greater specificity than the IgG-specific ELISA [0.86 (0.82-0.90)]. Given their high sensitivity and rapid turnaround time, Rls are a reliable means of excluding HIT at the point-of-care in patients with low or intermediate clinical probability. Additionally, some Rls have greater specificity than HIT ELISAs. In summary, IgG-specific Rls appear to have improved diagnostic accuracy compared with ELISAs in patients with suspected HIT and may reduce misdiagnosis and overtreatment.