Blood pressure differences between home monitoring and daytime ambulatory values and their reproducibility in treated hypertensive stroke and TIA patients

Background Guidelines recommend ambulatory or home blood pressure monitoring to improve hypertension diagnosis and monitoring. Both these methods are ascribed the same threshold values, but whether they produce similar results has not been established in certain patient groups. Methods Adults with mild/moderate stroke or transient ischaemic attack (N=80) completed two sets of ambulatory and home blood pressure monitoring. Systolic and diastolic blood pressure values from contemporaneous measurements were compared and the limits of agreement assessed. Exploratory analyses for predictive factors of any difference were conducted. Results Daytime ambulatory blood pressure values were consistently lower than home values, the mean difference in systolic blood pressure for initial ambulatory vs first home monitoring was -6.6 ± 13.5mmHg (p=<0.001), and final ambulatory vs second home monitoring -7.1 ± 11.0mmHg (p=<0.001). Mean diastolic blood pressure differences were -2.1 ± 8.5mmHg (p=0.03) and -2.0 ± 7.2mmHg (p=0.02). Limits of agreement for systolic blood pressure were -33.0 to 19.9mmHg and -28.7 to 14.5mmHg for the two comparisons, and for DBP were -18.8 to 14.5mmHg and -16.1 to 12.2mmHg respectively. The individual mean change in systolic blood pressure difference was 11.0 ± 8.3mmHg across the two comparisons. No predictive factors for these differences were identified. Conclusions Daytime ambulatory systolic and diastolic blood pressure values were significantly lower than home monitored values at both time points. Differences between the two methods were not reproducible for individuals. Using the same threshold value for both out-of-office measurement methods may not be appropriate in patients with cerebrovascular disease.