What constitutes controlled hypertension? Patient based comparison of hypertension guidelines

Objectives-To investigate and quantify the extent to which variations in guidelines influence assessment of control of hypertension. Design-Cross sectional study. Selected patients had hypertension assessed as controlled or uncontrolled with guidelines from New Zealand, Canada, the United States, Britain, and the World Health Organisation. Setting-18 general practices in Oxfordshire. Subjects-876 patients with diagnosed hypertension and taking antihypertensive drugs. Main outcome measures-Proportion of patients with controlled hypertension according to each set of guidelines. Results-The proportion of patients with controlled hypertension varied from 17.5% to 84.6% with the different guidelines after adjustment for the sampling method. All five sets of guidelines agreed on the classification for 31% (277) of the patients. The New Zealand guidelines calculate an absolute risk of a cardiovascular event. When this was taken as the standard half of the patients with uncontrolled hypertension by the United States criteria would be treated unnecessarily and 31% of those classified as having controlled hypertension by the Canadian guidelines would be denied beneficial treatment. Conclusions-Hypertension guidelines are inconsistent in their recommendations and need to make clear the absolute benefits and risks of treatment.