Measurement of blood pressure, ankle blood pressure and calculation of ankle brachial index in general practice

BACKGROUND: Low ankle brachial index (ABI) is a sensitive measure of 'burden' of atherosclerosis, indicating cardiovascular risk of the asymptomatic patient. Conventionally, ABI values <0.90 are considered pathological, indicating peripheral arterial disease. AIMS: The purpose of this study was to establish whether GPs after a short training course can reliably determine ABI compared to assessment in a specialized hospital department. DESIGN: Epidemiological observational study. METHODS: A total of 6 GPs and 12 general practice nurses from six practices were recruited for the study. Doppler measurements and ABI calculations were performed according to guidelines used by the Department of Nuclear Medicine, Odense University Hospital. RESULTS: On average, blood pressure measurements in general practice yielded lower values than those measured at the hospital. Differences in brachial and ankle blood pressure were -7 mmHg (-43 to 30 mmHg) and -14 mmHg (-63 to 33 mmHg), respectively. Sensitivity and specificity of ABI in general practice were 1.00 (0.87-1.00) and 0.79 (0.69-0.88), respectively. Predictive value of ABI measured <0.9 in general practice was 0.62 (0.46-0.76). CONCLUSIONS: Findings in general practice and at the Department of Nuclear Medicine were concordant with regard to the threshold value of ABI 0.9. However, this study does not warrant a recommendation of doppler measurements or assessment of ABI as screening or diagnostic procedure due to low specificity of assessments in general practice. Our results indicate a high number of false-positive tests if the method is applied for screening in general practice.