Hypertension and outcomes research: from clinical trials to clinical epidemiology.

Outcomes research seeks to identify effective methods of providing medical care. While randomized clinical trials (RCT) usually provide the clearest answers, they are often not done or not practicable. We still do not have RCT data about the effect of calcium-channel blockers and ACE inhibitors on major disease endpoints in patients with hypertension. Clinical trials that look at dose are rarely done, and those that use surrogate endpoints may provide misleading results. In part, meta-analyses that examine the effects of dose and treatment strategies in RCTs fill part of the void. Well-designed case-control studies can also provide useful information about the clinical effectiveness of anti-hypertensive therapies. Recent examples include the association of dose of diuretic therapy with the risk of primary cardiac arrest and the association of calcium-channel blockers with the risk of myocardial infarction. Observational studies also provide a means of assessing the effects of clinical trials on clinical practice. In the long term, outcomes research will need to assess not only what works but at what cost, and to be useful, the outcome of health-related quality-of-life will need to integrate the effects of death and major disease endpoints into measures that simply examine drug side effects.