Summary
The platelet factor 4/heparin ELISA has limited specificity for heparininduced thrombocytopenia
(HIT) and frequently does not provide same-day results. Rapid immunoassays (RIs) 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 RIs 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
RIs with each other and with ELISAs. Estimates of sensitivity and specificity for
each RI were calculated. Twenty-three articles, collectively involving six different
RIs, met eligibility criteria. All RIs exhibited high sensitivity (0.96 to 1.00);
there was wider variability in specificity (0.68 to 0.94). Specificity of the IgG-specific
chemiluminescent 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 polyspecific 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, RIs are a reliable means of excluding HIT at
the point-of-care in patients with low or intermediate clinical probability. Additionally,
some RIs have greater specificity than HIT ELISAs. In summary, IgG-specific RIs appear
to have improved diagnostic accuracy compared with ELISAs in patients with suspected
HIT and may reduce misdiagnosis and overtreatment.
Keywords
Heparin - immunoassay - meta-analysis - review - thrombocytopenia