Blood pressure randomized methodology study comparing automatic oscillometric and mercury sphygmomanometer devices: National Health and Nutrition Examination Survey, 2009-2010.

OBJECTIVES The mercury sphygmomanometer has been the gold standard used for obtaining blood pressure (BP) for the National Health and Nutrition Examination Survey (NHANES) from 1960 to the present. However, due to environmental concerns and an increased use of automated oscillometric BP devices, NHANES has been exploring an alternative to using the standard mercury sphygmomanometer (mercury) to measure BP. METHODS The accuracy of Omron HEM-907XL BP readings was compared with that of mercury BP device readings for gender, age group, race and ethnicity, and body mass index categories and cuff-size subgroups. Each person had three BP measurements per device recorded sequentially. The order of the devices and readers were randomly assigned. A total of 6,460 participants had three valid systolic readings, and 6,338 had three valid diastolic readings. RESULTS Omron and mercury measurements were correlated (r = 0.92, systolic BP; r = 0.79, diastolic BP). Overall, the mean between-device differences (Omron and mercury) were -1.6 mm Hg for systolic and -0.6 mm Hg for diastolic (p < 0.05 for both). The mean between-device differences were less than or about 2 mm Hg for each subgroup: gender, age group, race and ethnicity, and body mass index categories, and cuff-size subgroups. The exceptions were mean systolic between-device differences for those using the extra-large BP cuff (-3.1 mm Hg) and obese individuals (-2.6 mm Hg), and the mean diastolic between-device differences for the underweight group (-3.5 mm Hg). Assuming mercury to be the gold standard, between-device agreements for the frequency of high BP (140/90 mm Hg or more) and stage II high BP (160/100 mm Hg or more) were above chance (kappa = 0.72 for both). Omron underestimated the high BP frequency by 2.28% and stage II high BP frequency by 0.77%. CONCLUSIONS Lower estimates of high BP by the Omron device may require adjusting future national prevalence estimates accordingly to account for between-device differences.