Comparison of Three Measures of the Ankle-Brachial Blood Pressure Index in a General Population

555 Hypertens Res Vol.30 (2007) No.6 p.555-561 Original Article Comparison of Three Measures of the Ankle-Brachial Blood Pressure Index in a General Population Cheng-Rui PAN1), Jan A. STAESSEN2), Yan LI1), and Ji-Guang WANG1) The ankle-brachial blood pressure index (ABI) predicts cardiovasular disease. To our knowledge, no study has compared manual ABI measurements with an automated electronic oscillometric method in a population sample. We enrolled 946 residents (50.8% women; mean age, 43.5 years) from 8 villages in JingNing County, Zhejiang Province, P.R. China. We computed ABI as the ratio of ankle-to-arm systolic blood pressures from consecutive auscultatory or Doppler measurements at the posterior tibial and brachial arteries. We also used an automated oscillometric technique with simultaneous ankle and arm measurements (Colin VP1000). Mean ABI values were significantly higher on Doppler than auscultatory measurements (1.15 vs. 1.07; p < 0.0001) with intermediate levels on oscillometric determination (1.12; p < 0.0001 vs. Doppler). The differences among the three measurements were not homogeneously distributed across the range of ABI values. Doppler and oscillometric ABIs were similar below 1.0, whereas above 1.2 Doppler and auscultatory ABIs were comparable. In Bland and Altman plots, the correlation coefficient between differences in Doppler minus oscillometric ABI and ABI level was 0.21 (p < 0.0001). The corresponding correlation coefficient for Doppler minus auscultatory ABI was – 0.13 (p < 0.0001). In conclusion, automated ABI measurements are feasible in large-scale population studies. However, the small differences in ABI values between manual and oscillometric measurements depend on ABI level and must be considered in the interpretation of study results. (Hypertens Res 2007; 30: 555–561) Key Words: arteries, blood pressure, epidemiology, population Introduction The ankle-brachial blood pressure index (ABI) is a simple and noninvasive measure of the patency of the arteries of the lower extremities (1, 2) and predicts cardiovascular morbidity and mortality (3–6). ABI is usually measured by trained observers using a Doppler or auscultatory technique while ankle and brachial blood pressures are taken in the supine position (1). This manual approach has an intraobserver variability of approximately 10% (7). The Colin VP-1000 is an oscillometric device that allows simultaneous blood pressure measurements at the left and right brachial and posterior tibial arteries. A recent validation study in a clinical setting suggested that automated ABI measurement is accurate and requires little technical skill (8). The Food and Drug Administration recently approved the Colin device for clinical use. To our knowledge, no previous study From the 1)Centre for Epidemiological Studies and Clinical Trials, Ruijin Hospital, Shanghai Jiaotong University Medical School, Shanghai, P.R. China; and 2)Studies Coordinating Centre, Division of Hypertension and Cardiovascular Rehabilitation, Department of Cardiovascular Diseases, University of Leuven, Leuven, Belgium. This research was supported by the National Natural Science Foundation of China (grant 30571607), the Shanghai Commission of Science and Technology (grants 03JC14058 and 05ZR14100), the Shanghai Commission of Education (grants 04BC31 and the Dawn Project), and a grant from Studies Coordinating Center, Leuven (Belgium). Address for Reprints: Ji-Guang Wang, M.D., Ph.D., Shanghai Institute of Hypertension, Ruijin 2nd Road 197, Shanghai 200025, P.R. China. E-mail: Received November 7, 2006; Accepted in revised form January 25, 2007. 556 Hypertens Res Vol. 30, No. 6 (2007) Table 1. Characteristics of the Study Population Characteristic Anthropometrics Age (years) Body mass index (kg/m2) Brachial blood pressure (mmHg) Auscultatory systolic* Auscultatory diastolic* Oscillometric systolic† Oscillometric diastolic† Ankle blood pressure (mmHg) Auscultatory systolic* Auscultatory diastolic* Doppler systolic Oscillometric systolic† Oscillometric diastolic† Serum cholesterol (mmol/L) Total High density lipoprotein Men (n=465) Women (n=481) p value 46.4±15.7 22.0±2.8 43.5±14.8 22.2±2.9 0.004 0.37 130.4±23.2 78.6±11.3 133.4±22.8 77.7±12.9 130.8±25.9 78.9±12.7 133.5±25.7 77.3±14.7 0.79 0.71 0.96 0.68 141.0±26.3 80.8±11.5 150.4±26.8 154.4±28.2 80.0±12.6 138.7±29.5 82.0±12.9 148.3±30.4 148.4±32.5 79.0±14.2 0.23 0.14 0.26 0.002 0.23 4.88±0.96 1.58±0.49 4.79±0.98 1.55±0.37 0.16 0.32 *Auscultatory ankle blood pressure was available in 448 men and 432 women. †Simultaneous measurements obtained with an automated device (Colin,VP-1000). has applied an automated oscillometric technique on a large scale in an epidemiological setting. In the present study, we compared ABI distributions as measured by observers applying a Doppler or auscultatory technique to obtain consecutive blood pressure readings at the brachial and posterior tibial arteries against the ABI distribution as measured by an automated oscillometric device. Methods Study Population In the framework of an ongoing Chinese study on genes involved in hypertension (9, 10), we selected 8 villages from JingNing County, a rural area approximately 500 km south of Shanghai. The Ethics Committee of Ruijin Hospital and Shanghai Jiaotong University Medical School approved the study. We invited all inhabitants who were at least 12 years old to take part. Of 1,220 eligible residents, 981 gave informed written consent. For children aged 12–18 years, consent was also obtained from their parents. The participation rate was 80.4%. We excluded 35 subjects because they did not undergo both the Doppler and automated oscillometric ABI measurements. Thus, the number of subjects statistically analyzed totalled 946. Data Collection To ensure a steady state, the ABI measurements were obtained under standardized conditions in a quiet examination room after the subjects had rested for 10 min in the supine position. Participants refrained from smoking, heavy exercise, and alcohol drinking for at least 2 h prior to the examination. A single observer performed the manual blood pressure measurements in all subjects. She consecutively obtained two Doppler readings of systolic pressure, two auscultatory readings of systolic and two of diastolic pressure at the right posterior tibial artery, and finally two auscultatory readings of systolic and two of diastolic pressure at the right brachial artery. For the Doppler measurements, the observer used a hand-held 8 mHz A27116 probe (Hayashi Denki Corporation, Kawasaki, Japan), and for the auscultatory measurements a standard mercury sphygmomanometer. Cuffs used for the brachial and posterior tibial blood pressure measurements had a bladder size of 12 × 22 cm and 15 × 31 cm, respectively. A second observer obtained simultaneous oscillometric blood pressure readings at the right and left brachial and posterior tibial arteries, using the Colin VP-10 (...truncated)