title: Diagnostic accuracy of IgG-specific versus polyspecific enzyme-linked immunoassays in heparin-induced thrombocytopenia: a systematic review and meta-analysis.
abstract: Essentials Immunoassay specificity varies in heparin-induced thrombocytopenia (HIT) testing. This meta-analysis examined 9 studies that tested samples by both IgG and polyspecific methods. IgG-specific assays confer superior diagnostic accuracy compared with polyspecific assays. These results further support recommendations in favor of IgG-specific testing.
  
  
  
  Background There are conflicting data on whether the IgG-specific or polyspecific antiplatelet factor 4/heparin (PF4/H) enzyme-linked immunosorbent assay (ELISA) is preferred for the laboratory diagnosis of heparin-induced thrombocytopenia (HIT). Objectives To directly compare diagnostic accuracy of IgG-specific versus polyspecific ELISA in HIT. Patients/Methods A systematic search yielded nine studies comprising 1948 patients with suspected HIT tested by both IgG-specific and polyspecific ELISAs and a reference standard against which the diagnostic accuracy of the ELISAs could be measured. Study quality was assessed by QUADAS-2 criteria. Results There was identical sensitivity for IgG-specific and polyspecific ELISAs (0.97; 95% confidence interval (CI), 0.95-0.99) and superior specificity of IgG-specific compared with polyspecific ELISA (0.87 [0.85-0.88] vs. 0.82 [0.80-0.84], respectively). Performance was similar in subgroups using the serotonin release assay and a single commercial ELISA manufacturer. The negative predictive values of IgG-specific and polyspecific ELISA were similarly high (0.99, [0.99-1.00], but the positive predictive value was superior with IgG-specific compared with polyspecific ELISA (0.56 [0.52-0.61] vs. 0.32 [0.28-0.35], respectively). The positive likelihood ratio (LR) was higher in IgG-specific than polyspecific ELISA, although negative LRs were similar. There was high risk of quality concerns in domains of index test and reference standard. Conclusions The superior diagnostic accuracy of IgG-specific ELISA reinforces the ISTH-SSC recommendation for standardization of laboratory testing for HIT. Likelihood ratios of individual assays may be used in combination with clinical scoring systems as part of an integrated diagnostic algorithm for HIT.
authors.affiliation: Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: H D
authors.initials: HD
authors.lastname: Husseinzadeh
authors.affiliation: Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Gimotty
authors.affiliation: Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Pishko
authors.affiliation: Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: M
authors.initials: M
authors.lastname: Buckley
authors.affiliation: Departments of Pathology and Molecular Medicine, and Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: T E
authors.initials: TE
authors.lastname: Warkentin
authors.affiliation: Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.|Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Cuker
mesh_terms: D000368:Aged; D000465:Algorithms; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005260:Female; D006493:Heparin / Q000009:adverse effects* / Q000737:chemistry; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis* / Q000737:chemistry; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000097:blood; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012701:Serotonin / Q000378:metabolism; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis*
chemical_list: D007074:Immunoglobulin G; D012701:Serotonin; D010978:Platelet Factor 4; D006493:Heparin
keywords: diagnosis; enzyme-linked immunosorbent assay; heparin; thrombocytopenia; thrombosis