Laboratory monitoring for early detection of adverse drug reactions is recommended for many drugs. For patients treated with low molecular weight heparin (LMWH), the Summary of Product Characteristics (SPC) and clinical guidelines recommend to monitor the platelet count for heparin-induced thrombocytopenia (HIT), a potentially life-threatening adverse event, characterised by a typical drop in platelet count. When the platelet count drops without obvious explanation in these patients, testing for heparin-platelet factor 4 antibodies (HPF4-Ab) and initiating alternative anticoagulation are advised. In the current study adherence to recommended platelet count monitoring in clinical patients without thrombocytopenia-associated diseases treated with LMWH for at least five days at our institution, and adherence to recommended testing for HPF4-Ab and initiation of alternative anticoagulation in patients with potential HIT (defined as a drop of at least 50% in platelet count between days 5 and 14 following the start of LMWH treatment, or stopdate, whichever occurred first, compared to the highest platelet count within days 1–4) were investigated. Data from the Utrecht Patient Oriented Database (UPOD) were used for this retrospective cohort study. Inpatients exposed to the LMWHs dalteparin or nadroparin for at least five days during the period 2004–2005 were included. Patients with thrombocytopenia-related diseases were excluded. Firstly, adherence to recommended platelet count monitoring, based on recommendations from SPCs and clinical guidelines, was investigated. Secondly, the association between patient- and treatment characteristics and obtaining at least 2 platelets counts during treatment was investigated. Thirdly, adherence to recommended testing for HPF4-Ab and initiating treatment with danaparoid was investigated in patients with potential HIT. 6,804 patients with 7,770 episodes of LMWH treatment of at least five days were included. Adherence to the recommendations for platelet count monitoring from the SPC of nadroparin and dalteparin was 36.5% and 26.3% respectively. Adherence to the different platelet count monitoring recommendations from the 2002 clinical guideline on HIT was 23.0% and 41.5%. Obtaining at least 2 platelet counts during treatment was found to be strongly associated with ICU admission, previous UFH exposure, and a treatment duration of at least 10 days. There were 98 patients with potential HIT. Adherence to testing for HPF4-Ab in patients with potential HIT was 6.1%. Adherence to starting alternative anticoagulation in patients with potential HIT treatment was 0%. The results of this study suggest that adherence to recommendations for monitoring for HIT with LMWH is low at our institution. The results of this study justify to say that there is a need to think of appropriate actions for improving the awareness of HIT as an adverse reaction to LMWH, and to secure the safe use of LMWH.

Disclosures: No relevant conflicts of interest to declare.

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