Background: Most patients only have three measurements of blood pressure before being labelled as hypertensive. This may lead to inaccurate classification, unnecessary treatment and dilution in treatment benefit for the population.
Aim: To examine the accuracy of current methods of diagnosing mild hypertension, and to explore ways to improving targeting of antihypertensive treatment without entailing lengthy observation.
Design: Re-analysis of published data.
Methods: We tested current diagnostic methods using the data for 3965 individuals who were followed for a year in the placebo arm of the MRC Mild Hypertension Trial. We calculated the proportion selected for treatment by current methods and the diagnostic accuracy, using average blood pressure beyond 6 months as representing 'true' long-term blood pressure. We examined the benefit of averaging blood pressures, of prolonging observation modestly and of estimating within-person blood pressure variability.
Results: Prolonging observation to 3 months selects a smaller (by about 12%) proportion of the sample for treatment, a proportion similar to that defined as 'truly' hypertensive. The diagnostic accuracy of current methods is poor, with up to 69% discrepancy in classification. This discrepancy was improved by up to 18% in absolute terms by prolonging observation to 3 months and using average blood pressures. Identifying those individuals with low within-person variability allows marked improvement in the prediction of 'true' hypertension.
Discussion: Although some inaccuracy in the diagnosis of hypertension is inevitable, observation for 3 months, averaging blood pressures and estimating within-person blood pressure variability can markedly improve upon current practice.