Abstract Body (Do not enter title and authors here): Background: Blood pressure (BP) is a dynamic measure influenced by contextual and behavioral factors, with well-established evidence showing notable differences between office (OBP) and home (HBP) measurements. While OBP is often used to diagnose and manage hypertension and can be also used to identify eligible patients for clinical trials to enhance trial pragmatism through efficient use of electronic health records, caution is warranted against relying on a single OBP measurement for participant screening. In this study, we explored explanatory factors that associated with BP variability.

Hypothesis: We hypothesize that OBP and HBP will vary, and that variability cannot be explained by change in anti-hypertensives alone.

Methods: We compared OBP and HBP for 1000 patients above age 65 from two health systems participating in an NIH funded pragmatic, hybrid effectiveness implementation study. Patients were identified using a pragmatic recruitment strategy based on OBP. BP variability was defined as the SBP difference (i.e. SBP between qualifying OBP and baseline HBP) and further grouped into low (SBP less than 10 mmHg), moderate (SBP between 10 - 20 mmHg), and high (SBP more than 20 mmHg). We also examined changes in anti-hypertensives or their doses that could contribute to the BP variability.

Results: The study cohort had a mean (SD) age of 73.3 (5.6), with 61% female, 88% White, 10% Black and 2% Hispanic participants. The mean (sd) baseline DBP and SBP was 135 (17) mmHg, and 70 (16) bpm, respectively. The median (Q1, Q3) run-in period was 13 (8, 20) days between eligibility OBP and baseline visit with an HBP. 285, 292, 423 participants had low (0 – 10), moderate (10 – 20), and high (> 20) BP variability. Among those with moderate to high BP variability, 54 (8%) increased the use of antihypertensives (AHT) during the run-in period. In addition, female sex [1.62 (1.23 – 2.12)], low OBP [1.07 (1.05 – 1.08)], vision deficit [1.35 (1.01 – 1.81)], valvular disease [1.51 (1.03 – 2.21)] and smoking [0.50 (0.28 – 0.87)] are shown to be significantly associated with high BP variability.

Conclusion: These analyses highlight the substantial variability in BP readings in the same person and offers critical insights to inform the design of robust pragmatic trials in hypertension research. For screening for enrollment in clinical trials, multiple HBP readings, may be better than a single OBP reading.