This study assesses measurement variation in the measurement of ankle systolic blood pressure (ABP) when measured with Doppler ultrasound and with the strain gauge method. Ninety-seven patients were included. ABP was measured with Doppler ultrasound and with the strain gauge method. The methods were compared graphically by scatterplots and analyzed by paired t test, analysis of variance, and Pitman's paired variance ratio test. ABP was measured by strain gauge in all extremities, whereas no Doppler signal was obtainable in 7 limbs (4%). There was no systematic difference in measurements between the means of the two measurements. However, a substantial difference of more than 25 mm Hg was found in 15% of limbs and more than 20 mm Hg in 20%. In the majority of patients, measurements of ABP by Doppler ultrasound and the strain gauge method give similar results, but for a minority the discrepancy is substantial.
