Reliability of blood pressure measurement: the patient versus primary care workers

To evaluate the degree of inter-observer concordance in the blood pressure figures taken by a nurse and a doctor with a mercury sphygmomanometer and by the patient with a semi-automatic device. Observational, crossover study. A rural health centre. 318 people selected by systematic sampling. Pressure was taken in different ways by 3 different "observers" (0): the patient with a semi-automatic device (01), a nurse (02) and a family doctor (03). Inter-observer concordance was assessed through the Intra-class Correlation Coefficient (ICC) and the kappa index. 42.1%, 41.8% and 44.3% of patients had high blood pressure (> or = 140/90 mmHg) according to 01, 02 and 03, respectively. 33% were known to be hypertense. The ICC for systolic pressure was 0.81 (95% CI, 0.75-0.87) between 01 and 02; 0.84 (CI, 0.78-0.90) between 01 and 03; and 0.87 (CI, 0.82-0.92) between 02 and 03. The ICC for diastolic pressure was 0.67 (CI, 0.59-0.75), 0.72 (CI, 0.64-0.79) and 0.79 (CI, 0.72-0.86) for 01-02, 01-03 and 02-03, respectively. The kappa index was 0.53 (CI, 0.43-0.62) for 01-02; 0.60 (CI, 0.51-0.68) for 01-03; and 0.67 (CI, 0.58-0.75) for 02-03. Inter-observer concordance was good, with no substantial differences between the measurements made by the different observers. As the figures determined by the semi-automatic device were reliable, this is a good option for the follow-up and monitoring of hypertense patients.