Anticoagulant treatment of patients with chronic atrial fibrillation in primary health care in Sweden--a retrospective study of incidence and quality in a registered population

Abstract

Background: The number of patients receiving anticoagulant treatment is increasing. Chronic atrial fibrillation is the most common treatment diagnosis. The literature indicates a variable level of treatment control. Estimates of time within the therapeutic range have been recommended as a measurement of quality. Electronic patient records are providing clinical data that are useful for audits concerning anticoagulant treatment in real-life practice.

Objective: Our aim was to assess warfarin treatment for chronic atrial fibrillation in primary health care with regard to prevalence, incidence and quality.

Methods: A 2 year retrospective study was carried out of electronic patient records up to April 2002 in primary health care in Stockholm, including 12 primary health care centres with a registered population of 203 407. Main outcome measures were the number of new patients on wafarin treatment for chronic atrial fibrillation, and time within the therapeutic prothrombin range in the first 90 days of treatment using a linear interpolation method.

Results: In total, 827 patients were on warfarin treatment for chronic atrial fibrillation, giving a prevalence of 0.41%. Of these, 144 patients (study group) started treatment with warfarin for chronic atrial fibrillation during the study period, giving a yearly incidence of 0.07%. Their mean age was 73.1 years and 61.1% were men. There were 1721 prothrombin monitoring episodes registered in the first 90 days of treatment, on average once a week per patient. The average proportion of time within the therapeutic range was 54.1% (95% confidence interval (CI) 50.1-58.1), and the proportion of therapeutic tests was 50.2% (95% CI 47.8-52.6).

Conclusions: During the first, second and third months of warfarin treatment for chronic atrial fibrillation, patients were outside the therapeutic range time nearly half the time. There was a gender difference favouring men regarding initiation of treatment.