Comparison of nurse- and physician-determined clinic blood pressure levelsin patients referred to a hypertension clinic: implications for subsequentmanagement

Background When measuring BP, the physician induces a transient presser res ponse triggered by an alarm reaction. This 'white-coat effect' can influenc e therapeutic decisions. Whether it depends on the characteristics of the p hysician has not been evaluated. Objective To assess the 'white-coat effect' induced by several physicians i n a large sample of patients, using the blood pressure measured by trained nurses as a reference. Setting Referral hypertension clinic. Methods Patients were selected for the study if they had been referred for the first time to the clinic and if they had had their supine systolic/dias tolic brood pressure measured by a trained nurse (mean of the last two of t hree measurements taken every 1 min by an oscillometric device) and a physi cian (auscultatory method using a standard mercury sphygmomanometer). Physi cians were included in the study provided they had seen at least 25 patient s during the study period. The between-physician difference was assessed us ing linear regression analysis. Physician blood pressure was the dependent and nurse blood pressure was the independent variable. Results From 1 January 1997 to 15 September 1997, 1062 patients (50% male, aged 52 +/- 14 years), seen by 10 physicians (26-187 patients per physician ) and one nurse were included for analysis. The mean systolic/diastolic blo od pressure for physicians was 162 +/- 27/97 +/- 15 mmHg and that for the n urse was 155 +/- 24/88 +/- 14 mmHg. The nurse-physician differences were -6 mmHg (range -67 to +66) for systolic and -8 mmHg (-44 to +31) for diastoli c blood pressures. Major differences were observed between individual physi cians. Intercepts of the physician blood pressure versus nurse blood pressu re relationship ranged from 0.1-60.7 mmHg for systolic and from 13.3-55.3 m mHg for diastolic pressures. The slopes of this relationship differed less between physicians for systolic (0.72-1) than for diastolic pressures (0.56 -0.97). There was no difference between the patients seen by physicians in patients' age, sex, tobacco consumption, anti-hypertensive treatment or tar get-organ damage. Conclusion Large between-physician differences exist in the magnitude of th e white-coat effect that cannot be explained by patient characteristics. Ph ysicians should therefore not make any decisions based on blood pressure me asured manually during a first encounter. J Hypertens 2000, 18:391 - 398 (C ) Lippincott Williams & Wilkins.