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High incidence of positive heparin antibodies in a multidisciplinary intensive care unit


Heparin-induced thrombocytopenia (HIT) presents with thrombocytopenia and high risk for venous and/or arterial thrombosis, as an adverse effect of heparin (especially unfractioned).


To evaluate the incidence of positive heparin antibody test in a multidisciplinary ICU for the time period from 1 January 2006 to 30 November 2006.


We retrospectively reviewed all laboratory tests for heparin antibodies requested from the ICU for the period of January–November 2006. The blood sample analysis was performed with ELISA (Asserachrom® HPIA; Diagnostica Stago, Asnieres, France). All patients were receiving fractioned heparin subcutaneously for prophylaxis when indicated. Flushes of unfractioned heparin for catheter clotting prevention were given to all patients. Only 'positive' results were considered positive, whilst 'mildly positive' and 'uncertain' results were considered negative.


During that period 300 patients were admitted (mean duration of stay 15 ± 16 days, 25th–75th 4–22 days) to the ICU; 212 (70%) were survivors and 88 (30%) were nonsurvivors. All patients presenting with thrombocytopenia (platelets < 150,000/dl) or showing a decrease >50% of their admission day's platelet count were checked for heparin antibodies. Fifty-two samples retrieved from 48 patients suspicious for HIT were sent for heparin antibody analysis. Of the 48 patients checked, 15 (31%) were positive and 33 (68%) negative. Three of the suspected patients suffered from pulmonary embolism and were treated with therapeutic doses of i.v. unfractioned heparin; one of them was positive for heparin antibodies.


Our findings of high incidence of positive heparin antibodies may be mainly due to unfractioned heparin flushes. The use of heparin flushes with the new high-quality catheters and monitoring kit is questionable. Since low doses of unfractioned heparin could lead to the production of antibodies and subsequently to HIT, further studies should examine the risk-to-benefit ratio of the use of unfractioned heparin flushes in the ICU setting.

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Renieris, P., Gerovasili, V., El Ali, M. et al. High incidence of positive heparin antibodies in a multidisciplinary intensive care unit. Crit Care 11 (Suppl 2), P372 (2007).

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