Influence of the presence of doctors-in-training on the blood pressure of patients: a randomised controlled trial in 22 teaching practices.

Until now, no information is available about the effect of the presence of a doctor-in-training on a patient's blood pressure. We tested the hypothesis that the presence of a last year medical student might increase the blood pressure of the patient, in addition to the possible pressor response to the doctor-trainer. Normotensive and hypertensive patients with a minimum age of 25 years, visiting for any reason, were recruited at 22 teaching general practices. Patients were randomised into a 'trainee' group (n=133) and a 'no trainee' (n=129) group. The blood pressure was measured at two subsequent contacts. In the 'trainee' group, a student was present at the first visit only. In the 'no trainee' group, both visits were without student. Both groups had similar anthropometric characteristics at entry. At the first visit, systolic pressure was higher in the 'trainee' group than in the control group (139.5 vs 133.1 mmHg, P=0.004), with a similar trend for diastolic pressure (80.2 vs 77.8 mmHg, P=0.07). From the first contact to the follow-up visit, blood pressure decreased in the trainee group by 4.8 mmHg systolic (P<0.001) and 1.7 mmHg diastolic (P=0.03), whereas the corresponding changes in the control group were -0.1 mmHg (P=0.90) and +1.5 mmHg (P=0.03). Thus, the between group differences in these trends averaging 4.7 mmHg (CI 1.5-7.9, P=0.005) systolic and 3.2 mmHg (CI 1.1-5.3, P=0.003) diastolic were statistically significant. We conclude that in teaching-practices, the presence of a doctor-in-training has a significant pressor effect when an experienced general practitioner measures a patient's blood pressure. If confirmed, our findings imply that doctors should be cautious to initiate or adjust antihypertensive treatment when blood pressure readings are obtained in the presence of a student.