Quality control of the blood pressure phenotype in the Gaoyou population study

The Korotkoff approach is the only blood pressure (BP) measurement technique that allows contemporary data to be compared with decades of research. We randomly recruited 4483 people (53.3% women; mean age 52.1 years) from Gaoyou County, Jiangsu Province, China. Nine observers recorded the participants™ BP three times consecutively following Chinese Society of Hypertension guidelines. We assessed the BP phenotype based on five criteria: completeness of readings, percentage of identical BP readings, odd BP readings, end-digit preference and trends in BP from the first to the third reading. The proportion of participants with identical readings were 2.0% and 3.1% for systolic (SBP) and diastolic blood pressure (DBP), respectively. Among 26,898 BP values, 0.3% ended in an odd number. Among observers, the prevalence of identical readings varied from 0% to 5.3% for SBP and from 0% to 6.8% for DBP. Compared with the expected frequency of 20%, those ending in 0 had a lower frequency (17.2%; p < 0.001), whereas those ending in 8 had a higher frequency (22.4%; p < 0.001). From the first to the third measurement, SBP and DBP decreased (p < 0.001) by 0.87 and 0.55 mmHg, respectively. In conclusion, the procedures set up in the Gaoyou study produced a high-quality BP phenotype.