Evaluation of a new automated panel of assays for the detection of anti-PF4/heparin antibodies in patients suspected of having heparin-induced thrombocytopenia

Summary

Heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin treatment; the prognosis depends on early and accurate diagnosis, and prompt start of alternative anticoagulants. Because of high sensitivity, the commercially available immunologic assays are widely used, though not suited to be run on single samples and with a turnaround time of 2–3 hours. We evaluated two new, rapid, automated, semi-quantitative chemiluminescent immunoassays in HIT suspected patients: HemosIL® AcuStar HIT-IgG_(PF4-H) (specific for IgG anti- PF4/heparin antibodies) and HemosIL® AcuStar HIT-Ab_(PF4-H) (detecting IgG, IgM and IgA anti-PF4/heparin antibodies) (both from Instrumentation Laboratory). A total of 102 patients with suspected HIT were included; HIT was diagnosed in 17 (16.7%). No false negative cases were observed using either the HemosIL AcuStar HIT-IgG_(PF4-H) or the HITAb_(PF4-H) assay (sensitivity and negative predictive values = 100%; negative likelihood ratios <0.01). The specificity was higher for the He-mosIL AcuStar HIT-IgG_(PF4-H) in comparison with that of the HemosIL AcuStar HIT-Ab_(PF4-H) (96.5% vs. 81.2%). Higher values of the HemosIL AcuStar HIT-IgG_(PF4-H) were associated with increased probability of HIT. Patients with confirmed HIT and thrombotic complications had significantly higher levels of HemosIL AcuStar HIT-IgG_(PF4-H) than those without thrombotic complications. The HemosIL AcuStar HIT-IgG_(PF4-H) and HIT-Ab_(PF4-H) assays showed a very high sensitivity, and therefore they can reliably be used to rule out HIT in suspected patients. The diagnostic specificity was greatly increased by using the HemosIL AcuStar HITIgG_(PF4-H). Both the assays are reproducible (CVs <6%), rapid (turnaround time 30 minutes), automated, and semi-quantitative, and they can be run for single sample testing.

Keywords

Diagnosis - heparin-induced thrombocytopenia - HIT - immunoassay

• References

• 1 Greinacher A, Warkentin TE. Recognition, treatment, and prevention of heparin-induced thrombocytopenia: Review and update. Thromb Res 2006; 118: 165-176.
• 2 Warkentin TE. Heparin-induced thrombocytopenia. Hematol Oncol Clin North Am 2007; 21: 589-607.
• 3 Warkentin TE, Greinacher A, Koster A. et al. Treatment and prevention of hepa-rin-induced thrombocytopenia. Chest 2008; 133: 340S-380S.
• 4 Chong BH, Isaacs A. Heparin-induced thrombocytopenia: what clinicians need to know. Thromb Haemost 2009; 101: 279-283.
• 5 Nowak G. Heparin-induced thrombocytopenia (HIT II) – a drug-associated autoimmune disease. Thromb Haemost 2009; 102: 887-891.
• 6 Warkentin TE, Hayward CPM, Boshkov LK. et al. Sera from patients with hepa-rin-induced thrombocytopenia generate platelet-derived microparticles with procoagulant activity: an explanation for the thrombotic complications of hepa-rin-induced thrombocytopenia. Blood 1994; 84: 3691-3699.
• 7 Lewis BE, Wallis DE, Berkowitz SD. et al. Argatroban anticoagulant therapy in patients with heparin-induced thrombocytopenia. Circulation 2001; 103: 1838-1843.
• 8 Lubenow N, Eichler P, Lietz T. et al. Lepirudin for prophylaxis of thrombosis in patients with acute isolated heparin-induced thrombocytopenia: an analysis of 3 prospective studies. Blood 2004; 104: 3072-3077.
• 9 Warkentin TE. Heparin-induced thrombocytopenia: pathogenesis and management. Br J Haematol 2003; 121: 535-555.
• 10 Warkentin TE. New approaches to the diagnosis of heparin-induced thrombocy-topenia. Chest 2005; 127: 35S45S
• 11 Warkentin TE, Sheppard JA. Testing for heparin-induced thrombocytopenia antibodies. Transfus Med Rev 2006; 20: 259-272.
• 12 Greinacher A, Michels I, Kiefel V. et al. A Rapid and sensitive test for diagnosing heparin-associated thrombocytopenia. Thromb Haemost 1991; 66: 734-736.
• 13 Greinacher A, Amiral J, Dummel V. et al. Laboratory diagnosis of heparin-associated thrombocytopenia and comparison of platelet aggregation test, heparin-induced platelet activation test, and platelet factor 4 heparin enzyme-linked immu-nosorbent assay. Transfusion 1994; 34: 381-385.
• 14 Arepally G, Reynolds C, Tomaski A. et al. Comparison of PF4/heparin ELISA assay with the c-14-serotonin release assay in the diagnosis of heparin-induced throm-bocytopenia. Am J Clin Pathol 1995; 104: 648-654.
• 15 Bauer TL, Arepally G, Konkle BA. et al. Prevalence of heparin-associated anti-bodies without thrombosis in patients undergoing cardiopulmonary bypass surgery. Circulation 1997; 95: 1242-1246.
• 16 Pouplard C, May MA, Iochmann S. et al. Antibodies to platelet factor 4-heparin after cardiopulmonary bypass in patients anticoagulated with unfractionated heparin or a low-molecular-weight heparin : clinical implications for heparin-induced thrombocytopenia. Circulation 1999; 99: 2530-2536.
• 17 Pouplard C, Gueret P, Fouassier M. et al. Prospective evaluation of the '4Ts' score and particle gel immunoassay specific to heparin/PF4 for the diagnosis of hepa-rin-induced thrombocytopenia. J Thromb Haemost 2007; 05: 1373-1379.
• 18 Chong BH, Burgess J, Ismail F. The clinical usefulness of the platelet aggregation test for the diagnosis of heparin-induced thrombocytopenia. Thromb Haemost 1993; 69: 344-350.
• 19 Juhl D, Eichler P, Lubenow N. et al. Incidence and clinical significance of anti-PF4/heparin antibodies of the IgG, IgM, and IgA class in 755 consecutive patient samples referred for diagnostic testing for heparin-induced thrombocytopenia. Eur J Haematol 2006; 76: 420-426.
• 20 Deeks JJ, Altman DG. Diagnostic tests 4: likelihood ratios. Br Med J 2004; 329: 168-169.
• 21 Grimes DA, Schulz KF. Refining clinical diagnosis with likelihood ratios. Lancet 2005; 365: 1500-1505.
• 22 Greinacher A, Juhl D, Strobel U. et al. Heparin-induced thrombocytopenia: a prospective study on the incidence, platelet-activating capacity and clinical significance of antiplatelet factor 4/heparin antibodies of the IgG, IgM, and IgA classes. J Thromb Haemost 2007; 05: 1666-1673.
• 23 Greinacher A. Heparin-induced thrombocytopenia. J Thromb Haemost 2009; 07 (Suppl. 01) 9-12.
• 24 Amiral J, Wolf M, Fischer A. et al. Pathogenicity of IgA and/or IgM antibodies to heparin-PF4 complexes in patients with heparin-induced thrombocytopenia. Br J Haematol 1996; 92: 954-959.
• 25 Lindhoff-Last E, Gerdsen F, Ackermann H. et al. Determination of heparin-platelet factor 4-IgG antibodies improves diagnosis of heparin-induced thrombocy-topenia. Br J Haematol 2001; 113: 886-890.
• 26 Warkentin TE, Sheppard I JA, Moore JC. et al. Laboratory testing for the anti-bodies that cause heparin-induced thrombocytopenia: How much class do we need?. J Lab Clin Med 2005; 146: 341-346.
• 27 Pouplard C, Leroux D, Regina S. et al. Effectiveness of a new immuno-assay for the diagnosis of heparin-induced thrombocytopenia and improved specificity when detecting IgG antibodies. Thromb Haemost 2010; 103: 145-150.
• 28 Alberio L, Kimmerle S, Baumann A. et al. Rapid determination of anti-heparin/platelet factor 4 antibody titers in the diagnosis of heparin-induced thrombocy-topenia. Am J Med 2003; 114: 528-536.
• 29 Zwicker I J, Uhl L, Huang WY. et al. Thrombosis and ELISA optical density values in hospitalized patients with heparin-induced thrombocytopenia. J Thromb Haemost 2004; 02: 2133-2137.
• 30 Warkentin TE, Sheppard I J, Moore JC. et al. Quantitative interpretation of optical density measurements using PF4-dependent enzyme-immunoassays. J Thromb Haemost 2008; 06: 1304-1312.
• 31 Weiss BM, Shumway NM, Howard RS. et al. Optical density values correlate with the clinical probability of heparin induced thrombocytopenia. J Thromb Thrombolysis 2008; 26: 243-247.
• 32 Warkentin TE. Confirmatory procedure and other maneuvers to assess pathogenicity of platelet factor 4 (PF4)-dependent antibodies--distinguishing “signal” from “noise”. Thromb Haemost 2008; 100: 523-524.
• 33 Bakchoul T, Giptner A, Najaoui A. et al. Prospective evaluation of PF4/heparin immunoassays for the diagnosis of heparin-induced thrombocytopenia. J Thromb Haemost 2009; 07: 1260-1265.