Objective
The aim of this study was to evaluate the usefulness of Microlife WatchBP Office and the effect of increasing the number of measurements in the clinical evaluation of systolic interarm difference (IAD).

Patients and methods
Office blood pressure was measured simultaneously on both arms in 339 patients (85% diabetic) using the Microlife WatchBP Office, a fully automatic, oscillometric device. The patients included were all scheduled for ambulatory blood pressure measurement at the outpatient clinic of endocrinology at Silkeborg Regional Hospital, Denmark. Two successive sets of three individual measurements were made. A statistical analysis of variance was carried out on the measurements.

Results​
In the first set of measurements, the mean IAD was −0.3 mmHg and the prevalence of IAD greater than of equal to 10 mmHg was 9.1%. Only 7.6% of the patients with an IAD less than 10 mmHg in the first set of  measurements had an IAD greater than or equal to 10 mmHg in the second set of measurements. The 95% limits of agreement for the mean IAD for a single set of three measurements were ± 13.16 mmHg. The probability of detecting an IAD more than 10 mmHg only increased slightly with an increasing number of measurements.

Conclusion
A single set of triplicate measurements using Microlife WatchBP is an acceptable method for evaluating IAD as more measurements do little to improve the probability of detecting an IAD more than 10 mmHg because of high intraindividual variation.

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