Lipid lowering drugs in diabetes

Editor—The meta-analysis by Costa et al tackles clinically relevant issues by evaluating the effect of lipid lowering treatment in primary compared with secondary prevention and diabetic patients compared with non-diabetic patients.¹ The authors' conclusions as reported in the abstract may have important implications for guide-line recommendations and marketing of statins.

The abstract reports relative risk reduction as the measure of effect for the primary outcome. They seem impressive and reach significance. But we noticed that the absolute risk differences, in particular those in primary prevention, are much less impressive, and not all risk differences reach significance. The overall baseline risk in the non-diabetic population calculated from the event rate in the placebo group is 8%. The reduction that can be achieved through lipid lowering treatment in this group is 2%, and relative risk reductions.

Figure 1.

Relative effect measures cannot be interpreted without knowledge of the event rate without treatment.² The abstract of the meta-analysis does not provide this information. In addition, a measure of absolute effect (the risk difference), the most natural statistic to use when considering clinical significance, is not reported in the abstract. The abstract of this meta-analysis therefore does not provide clinicians with sufficient information to guide their practice. Moreover, it seems to lack objectivity, and the conclusion may even be misleading.

The BMJ's editors should protect the journal's readers from overoptimistic reporting that is not supported by the scientific data and safeguard the objectivity of abstracts published in the journal.