Comparison of automated office blood pressure measurement with 24-hour ambulatory blood pressure measurement.

Purpose: Although 24-hour ambulatory blood pressure measurement (24-h ABPM) is the most important method to establish true hypertension, in clinical practice often repeated automated office blood pressure (AOBP) measurements are used because of convenience and lower costs. We aimed to assess the agreement rate between a 30 and 60 min AOBP and 24-h ABPM.

Materials and methods: Patients with known hypertension (cohort 1) and patients visiting the neurology outpatient clinic after minor stroke or transient ischaemic attack (cohort 2) were selected. We performed AOBP for 30-60 min at 5-min intervals followed by 24-h ABPM and calculated average values of both measurements. Agreement between the two methods was studied with McNemar and Bland-Altman plots with a clinically relevant limit of agreement of ≤10 mm Hg difference in systolic BP.

Results: Our final cohort consisted of 135 patients from cohort 1 and 72 patients from cohort 2. We found relatively low agreement based on the clinical relevant cut-off value; 64.7% of the measurements were within the limits of agreement for 24-h systolic and 50.2% for 24-h diastolic. This was 61.4% for daytime systolic and 56.6% for daytime diastolic. In 73.5% of the patients, both methods led to the same diagnosis of either being hypertensive or non-hypertensive. This resulted in a significant difference between the methods to determine the diagnosis of hypertension (p < 0.0001).

Conclusion: We conclude that 30-60 min AOBP measurements cannot replace a 24-h ABPM and propose to perform 24-h ABPM at least on a yearly basis to confirm AOBP measurements.