Predictors for prophylactic antithrombotic prescribing in ischaemic heart disease and the impact of national guidelines

Objectives: Assessment of predictors for initiating prophylactic antithrombotic prescribing for patients newly diagnosed with ischaemic heart disease (IHD) and the impact of the introduction of national guidelines.

Design and setting: A retrospective case-control study was performed using pharmacy prescription data from 120,000 Dutch patients over a 5-year period. IHD patients were identified using as a marker multiple nitrate prescriptions [anatomical-chemical-therapeutic (ATC) code C01D] indicating chronic use. Initiation of antithrombotic therapy was likewise identified using ATC codes B01AA and B01AC (oral anticoagulants and thrombocyte aggregation inhibitors), prescribed within 6 months following the first nitrate prescription. Statistically significant (P <0.05) predictors were assessed using multivariable analysis considering patient, prescriber and medication characteristics.

Results: Of the 2598 patients who met specified inclusion criteria for newly diagnosed IHD, approximately 35% was not prescribed any type of antithrombotic therapy. Male patients [odds ratio (OR) 2.4, 95% confidence interval (CI) 2.0-2.9], patients with cardiovascular (other than IHD) and diabetic co-morbidity (OR 6.4, 95% CI 4.8-7.9 and OR 1.6, 95% CI 1.1-2.1, respectively) and patients using isosorbide mononitrate rather than isosorbide dinitrate as anti-ischaemic main therapy (OR 2.1, 95% CI 1.3-2.5) were most likely to be prescribed antithrombotic therapy. Furthermore, initiating antithrombotic prescribing was more likely after the introduction of national guidelines (OR 1.4, 95% CI 1.1-1.7).

Conclusions: Initiating antithrombotic prescribing in newly diagnosed II-ID patients can be predicted by patient gender, certain co-morbidity and main type of nitrate therapy. The introduction of national guidelines has resulted in an increase of prophylactic antithrombotic prescribing in accordance with their contents.