Clinical Usefulness of Combined use of Platelet Aggregation Test and Anti PF4-H. Antibodies Elisa test for the Diagnosis of Heparin Induced Thrombocytopenia

Abstract

Background. Heparin is the most commonly used drug in patients requiring therapeutic anticoagulation. But the use of heparin has serious side effects such as heparin-induced thrombocytopenia (HIT). The diagnosis of HIT is often difficult. This study was designed to test the diagnosis value of 2 laboratory tests: the platelet aggregation test and the ELISA test (Enzym Linked Immuno-Sorbent Assay).

Methods and Results. In order to evaluate the diagnostic value of these 2 tests, we prospectively performed both tests in all patients referred to our laboratory with suspected type II HIT, and compared their results with clinical outcome. Plasmas from 60 patients suspected of HIT, were tested for heparin-dependent platelet-reactive antibodies with a platelet agregation test (PAT) and with an ELISA which detects anti heparin platelet factor 4 antibodies (Anti PF4-H Ab). Among the 60 explored patients, the clinical diagnosis of HIT was confirmed in 27 patients by clinical criteria. In 16 of these 27 patients, PAT and anti PF4-H. Ab were both positive, and in the 11 other patients, one of the 2 tests was negative. In 29 of the 33 patients with no clinical HIT, PAT and anti PF4-H. Ab were both negative, in the 4 remaining patients, one of the 2 tests was positive.

Conclusion. For 75% of patients, biological results were concordant with the final clinical diagnosis. The combination of both tests is more reliable than the use of a single test; in the present series, all patients with positive results on both tests had clinically confirmed HIT, and all patients with negative results on both tests had not clinically confirmed HIT.

Keywords:

• Thrombocytopenia
• heparin
• platelets
• diagnosis
• anti PF4-H Ab