Interpretation of prospective trials in hypertension: do treatment guidelines accurately reflect current evidence?

OBJECTIVE: To review the findings of prospective controlled trials of antihypertensive treatment and determine whether the evidence they have provided is embodied satisfactorily in current national and international guidelines for hypertension management. MANAGEMENT GUIDELINES: Conventional guidelines all advise prompt treatment of moderate-to-severe hypertension and treatment of even mild hypertension in subjects with cardiovascular disease, target organ damage or diabetes, and in the elderly; and treatment of isolated systolic hypertension in the elderly. All acknowledge that evidence for efficacy and safety of treatment is strongest for thiazide diuretics and beta-blockers. UNCOMPLICATED MILD HYPERTENSION: Conventional guidelines all emphasize the importance of long-term blood pressure, measured over some months, for treatment decisions. However the blood pressure for routine treatment varies from 160/100 mmHg (British Hypertension Society) to 140/90 mmHg (Joint National Committee V). This dictates very large differences in the number of patients to be treated to prevent a cardiovascular disease event and in the proportion of the population to be treated, yet the reasons for these differences are not explicit. None of the conventional guidelines is entirely satisfactory. The more conservative British Hypertension Society policy may leave untreated some middle-aged men who ought to be treated. The more aggressive Joint National Committee V policy will lead to treatment of some young subjects who have only a remote chance of benefit, at very high cost, and possibly with adverse harm-benefit consequences. RISK-BASED GUIDELINES: Guidelines developed in New Zealand target absolute cardiovascular disease risk in mild hypertension and have the potential to correct this shortcoming of conventional guidelines. However they require further consideration as regards the number needed to treat which is acceptable to well-informed patients, the appropriate estimate of relative cardiovascular disease risk reduction by treatment in mild hypertension, the pattern of treatment which will emerge and their acceptability in ordinary practice.
CONCLUSION: Comparative evaluation will be needed to determine whether the outcome is better with conventional guidelines, which are simple but at the expense of accuracy, or with risk-targeted guidelines, which are more accurate but at the expense of simplicity.