Short-term reproducibility of ambulatory blood pressure measurements: a systematic review and meta-analysis of 35 observational studies.

Objective: A systematic review on the reproducibility of ambulatory blood pressure measurements (ABPM) has not yet been conducted. This meta-analysis compared 24-h/daytime/night-time SBP and DBP mean values and SBP/DBP nocturnal dipping status from ABPMs in participants with or without hypertension.
Methods: Ovid MEDLINE, EMBASE, and CINAHL Complete databases were searched for articles published before 3 May 2019. Eligible studies reporting a 24-h ABPM repeated at least once within 1 month were included. The mean daytime/night-time/24-h BP values, percentage of nocturnal dipping, and proportion of nondippers were compared between the first and second day of measurements, and the proportion of participants with inconsistent dipping status were estimated using a random effect model.
Results: Population-based analysis found a 0-1.1 mmHg difference between the first and second ABPM for 24-h/daytime/night-time SBP and DBP and 0-0.5% for percentage of SBP/DBP nocturnal dipping. The proportion of non-dippers was not different between the first and second ABPM. Intra-individual analysis found that the 95% limit of agreements (LOA) for SBP/DBP were wide and the 95% LOA for daytime SBP, common reference to diagnose hypertension, ranged -16.7 to 18.4 mmHg. Similarly, 32% of participants had inconsistent nocturnal dipping status.
Conclusion: ABPM had excellent reproducibility at the population level, favouring its application for research purposes; but reproducibility of intra-individual BP values and dipping status from a 24-h ABPM was limited. The available evidence was limited by the lack of high-quality studies and lack of studies in non-Western populations.