Blood pressure measurements in epidemiological surveys--time to change?

Blood pressure recordings in epidemiological surveys are usually obtained by non-ambulatory, multiple one-occasion, manual sphygmomanometric measurements by trained observers in study participants subjected to standardized examination conditions. High validity and reliability of blood pressure measurements ensure the comparability of study results obtained in different places and at different times, and have a major impact on the detection of correlates and determinants of blood pressure and hypertension. A blood pressure measurement quality assessment was performed within the multi-center collaborative WHO-MONICA Project investigating results of 47 surveys from various geographic regions of the world. In an overall summary assessment, six out of these 47 surveys were found to have had major measurement problems which prohibited their further inclusion in collaborative analyses. Most of the problems were associated with observer-related factors. Therefore, it was contended that automatic blood pressure measurement devices might be able to reduce and abolish most of these "nuisance" factors. In 1995, we had the opportunity to simultaneously study two independent random samples of men and women, aged 45 to 64 years, from the city of Augsburg in Southern Germany. One sample was examined by 16 observers with a random zero sphygmomanometer (MONICA Augsburg), the other sample (J.A.P. Study) was examined by two observers with an invasively validated, automatic oscillometric device (boso Oscillomat). In both surveys, blood pressure was measured three times under similarly standardized conditions. comparing the blood pressure results of the two surveys, the intra-individual measurement variation tended to be slightly higher with the Oscillomat than the random zero, and the population mean blood pressures and hypertension prevalences were found to be significantly lower with the Oscillomat. We conclude that manual measurements of blood pressure by sphygmomanometer should not be indiscriminately replaced externally validated automatic devices. The imponderabilities of automatic devices with varying technical principles have to be assessed in epidemiological settings weighed against recognized disadvantages of sphygmomanometry before any recommendations can be given as to changing the present epidemiological practice.