Risk scoring and thromboprophylactic treatment of patients with atrial fibrillation with and without access to primary healthcare data: experience from the Stockholm health care system.

BACKGROUND: Earlier validation studies of risk scoring by CHA2DS2VASc for assessments of appropriateness of warfarin treatment in patients with atrial fibrillation have been performed solely with diagnoses recorded in hospital based care, even though many patients to a large extent are managed in primary care.
METHODS: Cross-sectional registry study of all 43 353 patients with a diagnosis of non-valvular atrial fibrillation recorded in inpatient care, specialist ambulatory care or primary care in the Stockholm County during 2006-2010.
RESULTS: The mean CHA2DS2VASc score was 3.82 (4.67 for women and 3.14 for men). 64% of the entire cohort of patients with atrial fibrillation had the diagnosis in primary care (12% only there). The mean CHA2DS2VASc score of patients with a diagnosis only in inpatient care or specialist ambulatory care increased from 3.63 to 3.83 when comorbidities registered in primary care were added. In 2010 warfarin prescriptions were claimed by 47.2%, and ASA by 41.6% of the entire cohort. 34% of patients with CHA2DS2VASc=1 and 20% with CHA2DS2VASc=0 had warfarin treatment. ASA was more frequently used instead of warfarin among women and elderly patients.
CONCLUSIONS: Registry CHA2DS2VASc scores were underestimated without co-morbidity data from primary care. Many individuals with scores 0 and 1 were treated with warfarin, despite poor documentation of clinical benefit. In contrast, warfarin appears to be underused and ASA overused among high risk atrial fibrillation patients. Lack of diagnoses from primary care underestimated CHA2DS2VASc scores and may thereby have overestimated treatment benefits in low-risk patients in earlier studies.