HIT Test

From Tereza Munhoz, PUCRS:

Hi, George,  What your experience with HIT test? We intend to use the IL test. What do you know about it? Thanks for your attention.

Hello,Tereza, and thank you for your question. Heparin-induced thrombocytopenia with thrombosis (HIT) is a life-threatening side effect of unfractionated heparin therapy. HIT is caused by antibodies to heparin-platelet factor 4 (PF4) complexes, which may be detected by immunoassay techniques. The most common HIT assays are enzyme-linked immunosorbant assays (ELISA), which require lengthy incubations and are performed batchwise. These assays are sensitive, but non-specific, and are used to rule out suspected HIT. Positive ELISA results are confirmed using the serotonin release assay (SRA), performed at relatively few reference laboratories.

Akers Bioscience provides a manual, lateral immunoassay device that I described in aJanuary 4, 2013 response to Lynn Gingras. The Akers device provides a result within 10 minutes of sample application. Instrumentation laboratory provides automated methods, a turbidimetric ligand immunoassay (LIA), designed to be run on an ACL TOPS coagulometer, and a pair of chemiluminescent assays designed for the ACL AcuStar. Both methods provide a 30-minute turnaround time. The Akers device and the IL reagents detect the heparin/PF4 antibody with high sensitivity, yielding no false negatives, and may be used to rule out HIT. Positive results require confirmation using the SRA. The IL reagents are not available in the US, as they are currently under FDA review, so there is no clinical information available here. Here are two current articles describing the methodologies:

Legnani C, Cini M, Pili C, Boggian O, Frascaro M, Palareti G. Evaluation of a new automated panel of assays for the detection of anti-PF4/heparin antibodies in patients suspected of having heparin-induced thrombocytopenia. Thromb Haemost. 2010 ;104):402–9.

Davidson SJ, Ortel TL, Smith LJ. Performance of a new, rapid, automated immunoassay for the detection of anti-platelet factor 4/heparin complex antibodies. Blood Coagul Fibrinolysis. 2011;22):34–-4.