0843 Identifying the Minimum Number of Ambulatory Blood Pressure Measurements to Classify a Reliable Blood Pressure Dipping Status

Introduction Ambulatory blood pressure monitoring (ABPM) is recommended over office BP assessment as it enables quantification of the degree of nocturnal BP dipping (classifications: “dipping” = nighttime/daytime BP of < 0.9; “non-dipping” = ≥0.9), a robust predictor of future adverse events. However, ABPM can cause discomfort jeopardizing adherence to the 24-hour assessment. Current guidelines recommend at least 20/7 daytime/nighttime BP measurements for reliable classification of nocturnal dipping status, but recent reports suggest 8/4 daytime/nighttime measurements may be sufficient. This threshold for classification can reduce patient burden and potentially enhance clinical practice. We aimed to identify the minimum number of ambulatory BP measurements to determine a reliable dipping status. Methods Forty-three ostensibly healthy participants (50±10 years [mean±SD]) wore an ambulatory BP monitor for 24 hours with measurements every 20/30 minutes during the daytime/nighttime, respectively (maximum 48/16 daytime/nighttime measurements). We calculated each participant's dipping status using all available systolic BP measurements. We randomly selected 20-daytime plus 8-nighttime measurements, identified dipper statuses from all possibilities of 1-20 daytime and 1-8 nighttime measurements separately, and calculated the proportion of participants whose dipping status remained unchanged. We then evaluated all possible combinations starting with a minimum of 8 daytime/5 nighttime for consistency with participants’ full data set using a second random selection of 20/8 measurements Results We found that using 8-daytime (plus all available nighttime) measurements was sufficient for unchanged dipper status in 90% of possible combinations, and using 5-nighttime (plus all available daytime) measurements was sufficient for unchanged dipper status in 92% of possible combinations. Confirmatory analyses revealed that 8/5 daytime/nighttime combinations correctly identified dipper status in 84% of the >7 million combinations. 10/8 daytime/nighttime combination improved this to 86%, similar to 87% returned from the guidelines’ recommended combination of 20/7 daytime/nighttime measurements. Conclusion In ostensibly healthy people, current thresholds for ambulatory BP monitoring recommendation could result in ~13% misclassifications of dipping status compared to full datasets. However, considering that this measurement can cause discomfort and that dipping statuses can be unstable in 30% of individuals, 10/8 daytime/nighttime measurements may be a reliable alternative. Support (if any) NIH F32HL131308, R01HL163232, R01HL125893, R35HL155681, OHSU MRF and OFDIR.