Novel diagnostic assays for heparin-induced thrombocytopenia.

Abstract

Laboratory testing for heparin-induced thrombocytopenia (HIT) has important shortcomings. Immunoassays fail to discriminate platelet-activating from nonpathogenic antibodies. Specific functional assays are impracticable due to the need for platelets and radioisotope. We describe 2 assays that may overcome these limitations. The KKO-inhibition test (KKO-I) measures the effect of plasma on binding of the HIT-like monoclonal antibody KKO to platelet factor 4 (PF4)/heparin. DT40-luciferase (DT40-luc) is a functional test comprised of a B-cell line expressing FcγRIIa coupled to a luciferase reporter. We compared these assays to polyspecific and immunoglobulin (Ig)G-specific PF4/heparin enzyme-linked immunosorbent assays (ELISAs) in samples from 58 patients with suspected HIT and circulating anti-PF4/heparin antibodies. HIT was defined as a 4Ts score ≥ 4 and positive (14)C-serotonin release assay. HIT-positive plasma demonstrated greater mean inhibition of KKO binding than HIT-negative plasma (78.9% vs 26.0%; P < .0001) and induced greater luciferase activity (3.14-fold basal vs 0.96-fold basal; P < .0001). The area under the receiver-operating characteristic curve was greater for KKO-I (0.93) than for the polyspecific (0.82; P = .020) and IgG-specific ELISA (0.76; P = .0044) and for DT40-luc (0.89) than for the IgG-specific ELISA (P = .046). KKO-I and DT40-luc showed better discrimination than 2 commercially available immunoassays, are simple to perform, and hold promise for improving the specificity and feasibility of HIT laboratory testing.

• Authors: Adam Cuker, Ann H Rux, Jillian L Hinds, May Dela Cruz, Serge V Yarovoi, Isola A M Brown, Wei Yang, Barbara A Konkle, Gowthami M Arepally, Stephen P Watson, Douglas B Cines, Bruce S Sachais
• Journal: Blood (Blood) Vol. 121 Issue 18 Pg. 3727-32 (May 02 2013) ISSN: 1528-0020 [Electronic] United States
• PMID: 23446735 (Publication Type: Evaluation Study, Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Monoclonal
• Heparin

Topics

• Adult
• Aged
• Aged, 80 and over
• Antibodies, Monoclonal (immunology)
• Cells, Cultured
• Enzyme-Linked Immunosorbent Assay
• Female
• Hematologic Tests
• Heparin (adverse effects)
• Humans
• Male
• Middle Aged
• Thrombocytopenia (chemically induced, diagnosis)