title: Using HitAlert flow cytometry to detect heparin-induced thrombocytopenia antibodies in a tertiary care hospital.
abstract: We aimed to assess the utility of HitAlert flow cytometry as a diagnostic functional heparin-induced thrombocytopenia (HIT) assay in a tertiary care hospital. The 4Ts score was used to assess pretest probability of HIT in 37 patients. Serum was analysed for HIT antibodies by the flow cytometry HitAlert assay. Results were compared with an antigenic assay, the particle gel immunoassay, PaGIA ID PF4/Hep Ab assay; and two functional assays, the Multiplate whole blood impedance aggregometry assay (WBIA), and the serotonin release assay (SRA). Flow cytometry was positive in 14 out of 37 patients, including zero out of eight, five out of 19 and nine out of 10 in the low, intermediate and high-risk groups by 4Ts score, respectively. Using the SRA as a 'gold standard', flow cytometry has a sensitivity of 81% and a specificity of 100% for the diagnosis of HIT. The other functional assay (WBIA) had similar sensitivity (81%) and specificity (90%) to flow cytometry. In contrast, the PaGIA maintained a high sensitivity of 100% but a specificity of only 20%. The improved specificity of flow cytometry over the antigenic assay was most marked in the 4T intermediate-risk group in which similar results were obtained between all three functional assays. We demonstrate that compared with an immunological assay (PaGIA), flow cytometry can improve the specificity of laboratory diagnosis of HIT without loss of sensitivity using SRA as a standard. Flow cytometry may have a role in the first-line laboratory diagnosis of HIT, especially when combined with an immunological assay such as PaGIA.
authors: Haematology Department, Pathology Queensland, Princess Alexandra Hospital, Australia.
authors: Connie
authors: C
authors: Solano
authors: Howard
authors: H
authors: Mutsando
authors: Marlene
authors: M
authors: Self
authors: Marie-Christine
authors: MC
authors: Morel-Kopp
authors: Peter
authors: P
authors: Mollee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D006493:Heparin / Q000009:adverse effects; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000097:blood*; D012680:Sensitivity and Specificity; D012701:Serotonin / Q000097:blood / Q000378:metabolism; D062606:Tertiary Care Centers; D013921:Thrombocytopenia / Q000097:blood / Q000139:chemically induced / Q000175:diagnosis* / Q000276:immunology; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D001323:Autoantibodies; D012701:Serotonin; D010978:Platelet Factor 4; D006493:Heparin