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Clinical Epidemiology

Clinical Articles, Lead Article

Estimating AF prevalence with electronic health data

The Swedish National Patient Register (NPR), and an electrocardiography (ECG) database are useful tools for estimating disease prevalence, according to a study1 published recently in Clinical Epidemiology.

Searching the electrocardiography (ECG) database enhanced the detection of atrial fibrillation (AF), revealing  a high prevalence of AF especially among the elderly, according to authors from Umeå University, Sweden. The reliability of the National Patient Register (NPR) was also high, with a relatively low proportion of false positives and negatives, they found.

The study was conducted in a region of northern Sweden (population n=75,945) which consists of one hospital and 11 primary health care centers. Subjects with AF were identified by searching the combined inpatient and outpatient International Classification of Diseases (ICD)-based NPR (ICD-10 code I48) and an ECG database with computer-interpreted AF from January 1, 2004 to December 31, 2010. All identified cases with AF were validated.


Dr Matt Fay (Westcliffe Medical Centre, Yorkshire)

AF was confirmed in 2,274 patients. The overall prevalence was 3.0% (3.4% in men and 2.6% in women). AF prevalence rose steadily with age, and was 16.8% in patients aged 75 years and older and 21.9% in patients 85 years and older. Of all patients with validated AF, the NPR identified 93.2%. The ECG database identified an additional 6.8%, of which 81% were over 70 years of age. According to the NPR, the proportion of false positives and false negatives was 3.5% and 6.8%, respectively. The corresponding figure for the ECG database was 11.3% and 9.2%, respectively.

Speaking to BJC Arrhythmia Watch, UK general practitioner Dr Matt Fay (Westcliffe Medical Centre, Yorkshire) commented on the study’s implications for British healthcare: “This study which looks at the practicalities of finding AF in a population that has already undergone some form of cardiac assessment highlights the inefficiencies of ECG acquisition in the UK, which is neither quality assured or centrally gathered.”

“It also highlights the need to do a clinical audit outside the QOF contractual data. The GRASP-AF data set has shown those patients who have suffered from AF who had been coded as ‘AF resolved,’ due to previous rhythm corrective intervention, are being denied stroke risk stratification as they are removed from the QOF searches and registers”.


1. Norberg J, Bäckström S, Jansson JH, Johansson L. Estimating the prevalence of atrial fibrillation in a general population using validated electronic health data. Clin Epidemiol 2013;5:475–81.

Published on: December 20, 2013

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