The primary purpose of meta-analyses is to address a relevant scientific and clinical question by combining data from multiple studies. Typically, meta-analyses are needed when individual studies are underpowered to address the primary question of interest. Chris Palmer (March 3, p 715)1
and Morris Brown (March 3, p 715)2
attempt to identify the reasons why our meta-analysis3
and that of the Blood Pressure Lowering Treatment Trialists (BPLTT)4
might have reached different conclusions.
In their convoluted reasoning, Palmer and Brown miss the obvious reason for a difference: the two meta-analyses addressed different primary questions. When the data presented in each meta-analysis are used to address the same question, the findings are remarkably similar—a conclusion that should occasion no surprise.
Our main objective was to find out whether calcium antagonists used as first-line therapy are better than, equal to, or worse than other treatments in lowering the incidence of cardiovascular complications of hypertension. The answer to this question is important for members of formulary committees, framers of treatment guidelines, health economists, and all clinicians treating patients with hypertension. We used the totality of available evidence to compare calcium antagonists with other agents in nine trials. The BPLTT meta-analysis used data from six of those trials and excluded the other three. When the BPLTT data are used to address our question about the use of calcium antagonists as first-line agents (table 1
), the findings are nearly identical to ours: calcium antagonists are worse than other drugs for the prevention of the outcomes of myocardial infarction, coronary heart disease, and congestive heart failure. In the two analyses directed at the same question, the treatment differences between calcium antagonists and other drugs were within the play of chance for the outcomes of stroke and all-cause mortality (p>0·05). For the outcome of combined major cardiovascular events, both analyses show an increased risk associated with calcium antagonists, although only one reaches conventional levels of significance. To a large extent, the two CI for major cardiovascular events are overlapping.
Comparison of calcium antagonists with other drugs for cardiovascular outcomes
The question of the risks or benefits of calcium antagonists for the outcome of stroke remains an open question. For the prevention of myocardial infarction, coronary heart disease, and congestive heart failure, however, the totality of scientific evidence is strong and consistent: low-dose diuretics, β-blockers, and angiotensin-converting-enzyme inhibitors are better than calcium antagonists as first-line agents for the treatment of hypertension.