Multiple-outcomes meta-analysis of treatments for periodontal disease.

The results of periodontal therapy vary by disease severity, outcome measure, and method of data analysis. Several clinical trials and a subsequent meta-analysis have demonstrated that, for teeth with severe disease, surgery decreases probing depth (PD) and increases attachment level (AL) more than non-surgical treatment. For other disease levels, the choice of therapy depends on the outcome measure. When clinical trials use two or more outcome measures (such as PD and AL), investigators ordinarily analyze each outcome separately. When the correlations are incorporated among the outcomes, a meta-analysis can use generalized-least-squares (GLS) regression to analyze multiple outcomes jointly. We applied the GLS multiple-outcomes model in a meta-analysis of 5 trials comparing surgical and non-surgical periodontal treatments, each assessing the outcomes PD and AL one year after treatment. The clinical conclusions are similar to those reported earlier, but our estimates of the relative benefits of surgical and non-surgical treatment should be more accurate, because the GLS method takes into account correlation between AL and PD. When correlations between the two outcomes rise, as they do with increasing severity of disease, the GLS estimates depart from those derived from separate analyses of PD and AL.