Introduction and objectives: The white coat phenomenon is said to occur when the difference between systolic/diastolic blood pressure measured during visits to the doctor's office and in ambulatory recordings is greater than 20/10. These absolute differences, known as the white coat effect, may lead to normotensive patients being classified as having white coat hypertension (WCH). We used ambulatory blood pressure monitoring (ABPM) to monitor the prevalence and response (white coat effect, white coat hypertension or white coat phenomenon) in patients during pharmacological treatment for grade 1 or 2 hypertension, and 4 weeks after treatment was suspended under medical supervision.
Patients and method: Ambulatory blood pressure monitoring was used in 70 patients with hypertension that was well controlled with treatment. Blood pressure was recorded during treatment (phase 1) and 4 weeks after treatment was stopped (phase 2).
Results: 18 (26%) of the 70 patients did not participate in phase 2 because when medication was withdrawn, their blood pressure values became unacceptable and it was necessary to restart treatment. The white coat effect was significantly stronger in phase 1, and the prevalence of white coat phenomenon and white coat hypertension did not differ significantly between phases. At the end of phase 2 the prevalence of white coat hypertension was 33%.
Conclusions: Withdrawal of antihypertensive medication in patients with well controlled grade 1 or grade 2 hypertension did not significantly modify the prevalence of white coat phenomenon or white coat hypertension. The white coat effect was greater while patients were on pharmacological treatment. One third of our patients were considered to have been mistakenly diagnosed as having hypertension.