Objective

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.