A Study of the White-Coat Phenomenon in Patients with Primary Hypertension

37 Hypertens Res Vol.31 (2008) No.1 p.35-39 Original Article A Study of the White-Coat Phenomenon in Patients with Primary Hypertension Ning ZHU1), Minrui BU2), Dan CHEN1), Tiejun LI3), Jianing QIAN4), Qin YU5), Qiang CHEN1), Chao WAN1), Hong QU1), Mingxia ZHU1), and Xiaoli ZOU1) The objective of this study was to evaluate whether the discrepancy between clinic and home blood pressure (BP) in hypertensive subjects would disappear or diminish in magnitude if the BP measurement was taken under controlled conditions differing only with respect to location (clinic vs. home). Three hundred and sixty-seven patients aged 34–84 years with primary hypertension were enrolled. All of the patients or their spouses were taught to measure BP correctly with their own sphygmomanometer at home. The home BP value (HBP) was calculated as the average of 45 readings over 15 days. On days 6, 12, and 18 of the measurement period, rather than measuring their BP at home, patients and their spouses were asked to visit the hospital at the usual time of their BP measurement and to bring their own sphygmomanometer. The clinic BP value (CBP) was calculated as the average of the 9 readings taken on these visits by the patients or their spouses. The “white-coat phenomenon” (WCP) was considered to be present when the difference between the CBP and HBP was greater than 20/10 mmHg. The mean reading of home systolic/diastolic BP was 134.7/79.1 mmHg and the mean reading of clinic systolic/diastolic BP was 149.8/86.4 mmHg. In the total subject group, the prevalence rate of WCP was 31%–35% if the WCP was defined as ΔBP (CBP – HBP) ≥ 20 mmHg/10 mmHg. In conclusion, ruling out the influence of different factors, including time of day, the sphygmomanometer, the individual taking the BP measurement, the climate, and the patients’ health or mood, the WCP was still found to exist to a statistically significant degree. This study indicated that teaching patients to measure their own BP at home is an effective procedure to obtain a more accurate result of their BP level. It also helped to involve the patients more actively in controlling their hypertension. ( Hypertens Res 2008; 31: 37–41) Key Words: hypertensive, white-coat phenomenon, home blood pressure measurement Introduction The factors contributing to the disparities between home and clinic blood pressure (BP) readings have been explored by Ayman and Goldshine (1, 2), but the underlying reasons for the phenomenon have remained unclear. Mancia et al. (3) used continuous intra-arterial recording of pressure in hospitalized patients and found that, as the physician approached the patients and placed the BP cuff on their arms, there was an immediate, dramatic, and clinically significant elevation in BP, which persisted throughout the entire procedure. The phenomenon is now known as the white-coat effect (WCE) or white-coat phenomenon (WCP). Most studies of WCE have From the 1)Department of Cardiovascular Medicine, The Second Affiliated Hospital of Dalian Medical University, Dalian, P.R. China; 2)The Chest Hospital of Ben Xi Iron and Steel Company, Ben Xi, P.R. China; 3)The First Sanatorium of ShenYang Command, Dalian, P.R. China; 4)The University of Toronto, Toronto, Canada; and 5)The Affiliated Zhongshan Hospital of Dalian University, Dalian, P.R. China. Funding was received from the Department of Cardiovascular Medicine, The Second Affiliated Hospital of Dalian Medical University, Dalian 116027, P.R. China. Address for Reprints: Ning Zhu, M.D., The Second Affiliated Hospital of Dalian Medical University, 467 ZhongShan Rd., Dalian 116027, P.R. China. E-mail: Received January 4, 2007; Accepted in revised form August 3, 2007. 38 Hypertens Res Vol. 31, No. 1 (2008) Table 1. Characteristics of the 367 Hypertensive Patients Item Men/women Women (%) Age (years) Age of men (years) Age of women (years) Course of hypertension (years) Body mass index (kg/m2) Blood lipids TC (mmol/L) TG (mmol/L) HDL-C (mmol/L) LDL-C (mmol/L) Apo-A (mmol/L) Apo-B (mmol/L) Blood glucose Echocardiogram IVS (mm) LVPW (mm) LA (mm) LV (mm) LVEF (%) Occupation (%) Teacher and scientist Cadre Worker Others Medicine taken (%) Diuretic β-Blocker CCB ACEI ARB Total (n = 367) ΔSBP ≥ 20 mmHg (n = 116) ΔSBP < 20 mmHg (n = 251) 129/238 64.8 63.72 ± 9.48 64.78 ± 10.44 63.15 ±8.81 8, 3–50 25.17±3.54 40/76 65.8 63.00 ± 9.69 64.54 ± 11.04 62.21±8.89 8, 3–50 24.47±3.59 89/162 64.8 64.05 ± 9.34 64.89 ± 10.31 63.59±8.76 8, 3–44 25.49±3.47 5.52±1.20 1.82±1.10 1.39±0.39 3.18±1.00 1.38±0.28 1.04±0.57 5.78±1.46 5.68±1.08 1.73±0.85 1.39±0.33 3.44±0.98 1.39±0.27 1.10±0.53 5.78±1.76 5.46±1.24 1.86±1.18 1.40±0.41 3.07±0.99 1.38±0.29 1.01±0.59 5.78±1.30 11.00±1.90 10.54±1.47 33.12±7.81 43.36±7.11 56.77±5.14 10.89±1.57 10.36±1.20 32.72±8.51 43.26±10.00 57.52±5.81 11.06±2.04 10.63±1.54 33.31±7.50 43.41±5.28 56.39±4.80 41.96 23.34 11.04 23.66 36.90 25.20 12.60 25.20 46.20 21.96 10.00 21.90 44.14 42.51 54.22 11.17 3.00 34.20 39.30 44.40 14.50 1.70 48.80 44.00 58.80 9.60 3.60 Data are expressed as mean±SD or mean, range. TC, total cholesterol; TG, triglyceride; HDL-C, high-density lipoprotein cholesterol; LDL-C, low-density lipoprotein cholesterol; Apo-A(B), apolipoprotein-A(B); IVS, interventricular septum; LVPW, left ventricular posterior wall thickness; LV, left ventricle; LVEF, left ventricular ejection fraction; CCB, calcium-channel blocker; ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin-receptor blocker. used ambulatory blood pressure monitoring (ABPM) in normotensive subjects. In the present study, however, we focused on aged hypertensive patients receiving antihypertension treatment, since an “abnormal” rise in clinic BP (CBP) in treated hypertensive patients can lead to a misdiagnosis of refractory or resistant hypertension (4). In such cases, clinicians might increase the dosage of antihypertensive drugs or implement further unnecessary medication, resulting in adverse side effects and added expense. Our aims were thus to evaluate the discrepancy between home BP (HBP) and CBP in hypertensive patients on antihypertensive treatment, and to clarify the magnitude of WCP in hypertensive subjects and its association with age, gender, occupation, and medication. We planned to do this by repeatedly taking BP at the same hour, with the same sphygmomanometer, and by the same person, but at two different locations (the home and clinic). Methods Patients A total of 367 patients from the outpatient hypertensive clinic were enrolled. All patients had been diagnosed with primary hypertension, had been receiving antihypertensive treatment for a long period of time (ranging from 3 to 50 years), and had a stabilized BP with no change in recent medication. Patients Zhu et al: WCP in Hypertensives 39 Table 2. WCP Components in Both Genders Age (years) Men Subjects (n (%)) Women ΔSBP≥20 mmHg ΔDBP≥10 mmHg (n (%)) (n (%)) Subjects (n (%)) ΔSBP≥20 mmHg ΔDBP≥10 mmHg (n (%)) (n (%) (...truncated)