Skip patterns in DINAMAP-measured blood pressure in 3 epidemiological studies

Blood pressure measured by the oscillometric, automated device DINAMAP in 3 large population-based studies sponsored by the National Heart, Lung, and Blood Institute (The Atherosclerosis Risk in Communities Study, The Family Heart Study, and the Hypertension Genetic Epidemiology Network Study) were reviewed to determine an apparent skip pattern in the measurement values. Across the 3 studies, 2 different DINAMAP models were evaluated on >350 000 different blood pressure measurements. Measurements were taken in various positions, on both arm and ankles, and under various conditions (eg, resting and during stress). The following systolic blood pressure values were consistently skipped by the device: 89, 119, 120, 124, 125, 130, 140, 141, 150, 160, 170, 180, 190, and 200 mm Hg. No skip pattern was detected for diastolic blood pressure. Pulse data, which were only available in the Hypertension Genetic Epidemiology Network Study, also showed the following skipped values: 95, 99, 103, 106, and 109 bpm. Consultation with the manufacturer, the Critikon Corporation, indicated that the use of an algorithm designed to improve the accuracy of the DINAMAP device prevents these values from being displayed. Assessment of the extent and direction of bias caused by the skipped values is difficult, given that the algorithm is proprietary. While the implications of the skipped values are not clear, it is important for clinicians and researchers to be aware of this feature.