Clinical characteristics and laboratory testing of patients with suspected HIT: a survey on current practice in 11 university hospitals in France.

Unlabelled: We undertook a survey of French university hospital hematological laboratories to ascertain the clinical characteristics of patients with suspected HIT, the laboratory tests performed, and the therapeutic strategy adopted in current practice.

Methods: A standardized medical records database for patients with suspected HIT was sent to 19 laboratories. During two months, all consecutive patients for whom a biological test was performed were included.

Results: 169 patients were included, 27 (16%) patients having a final diagnosis of HIT. At the time HIT was suspected, the heparin duration and the level of thrombocytopenia were similar in HIT- positive and HIT-negative groups. The use of unfractionated heparin, a therapeutic heparin dose regimen and the presence of thrombotic complications were significantly more frequent in HIT-positive patients. When the heparin dose regimen was taken into account, only thrombotic complications under a therapeutic dose regimen were significantly increased in HIT-positive patients. Eighty-six percent of patients presented at least one alternative diagnosis of thrombocytopenia without significant difference between the two groups. Laboratory tests were performed after a mean of 0.3days and mainly consisted of antigen assays. At the time HIT was suspected, heparin was stopped in 56 (33%) patients, being replaced mainly by danaparoid. Only three laboratories declared they usually received all the necessary clinical information to establish the likelihood of HIT.

Conclusion: In current practice in France, the clinical probability of HIT is rarely established, leading to systematic requests for laboratory HIT tests.