WHITE COAT EFFECT AND WHITE COAT HYPERTENSION IN PATIENTS REFERRED TO AMBULATORY BLOOD PRESSURE MEASUREMENTS: PP.25.30

Introduction: The transient blood pressure (BP) rise during clinical visits is referred to as white-coat effect (WCE), and can be identified using ambulatory blood pressure (ABP) measurement. The aims of this study were to assess the magnitude of WCE and the prevalence of white coat hypertension (WCH) in patients referred to the hypertension clinic for ABP from primary care physicians. Material and Methods: Information was gathered from 498 randomly selected patients who underwent ABP measurements using Spacelab 90207 during a 3-year period from 1998-2000. WCE was calculated as the difference between referral BP and daytime ABP, and between 1st h ABP (average of the 3 first readings) in the outpatient clinic and daytime ABP. WCH was defined as office SBP reading => 140 and/or DBP => 90 mmHg, but normal 24h ABP < 125/80 mmHg. Results: The patients (52% women, 55.8 ± 14.8 years, mean ± SD) had referral blood pressure 166.3 ± 22.4/98.8 ± 10.9 mmHg and daytime ABP 142.6 ± 16.4 / 86.6 ± 11.4 mmHg. The WCE using referral BP was 23.5 ± 22.0, and 11.6 ± 12.4 mmHg using 1st h ABP. The difference between referral BP and 1st h ABP was 9.4 ± 22.1/1.7 ± 13.0 mmHg. No gender difference appeared in WCE (24.0 ± 22.5 vs 23.1 ± 21.5 mmHg). WCE was related to age (r = 0.21, p < 0.001). Clinical significant WCE defined as a difference> 15 mmHg between office BP and ABP was present in 42% of all patients. WCH was present in 19.1%. Conclusion: In this patient population, WCE was pronounced and WCH was present in approx 1/5th of the patients. ABP measurement should be undertaken routinely in patients with hypertension to ensure proper diagnosis and avoid overtreatment, especially in the elderly patients.