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Composite Analyses Versus Individual Endpoints Of Osteoarthritis Equal

Composite analyses of osteoarthritis clinical endpoints versus individual endpoints do not increase precision to discriminate active from placebo treatment.

This is the finding of study of the precision of composite measures of osteoarthritis (OA) efficacy compared with that of individual endpoints.

Clinical studies of OA generally use various endpoints to evaluate a spectrum of disease manifestations. As compared with individual endpoints, a composite measure might 1) provide a uniform outcome measure of OA efficacy with greater face validity, 2) address multiplicity, and 3) enhance precision.

These researchers reanalysed three six-week, placebo-controlled, double blind parallel group studies of the cyclooxygenase-2 (COX-2) specific inhibitor rofecoxib.

Average change from baseline at study weeks two, four and six was assessed for 10 individual response variables. These included patient and investigator global assessments, WOMAC 3.0V OA Index pain, stiffness and physical function subscales, graded study joint tenderness, and rescue analgesic use.

Researchers evaluated relationships among variables using pairwise correlations and principal components analysis. The precision of variables to differentiate rofecoxib from placebo was evaluated using effect size.

Correlations among all pairs of response variables ranged from 0.5 to 0.9, except those with tenderness (0.4 to 0.6) and those with analgesic use (0.2 to 0.4).

The first principal component explained about 70 percent of the total variability, with weights generally similar.

These results indicate nearly all measures are closely related.

Based on these results, various linear combinations of the nine endpoints were formed and their precision to discriminate active treatment from placebo was compared to that of the individual endpoints.

Effect sizes of the individual endpoints ranged from 0.6 to 1.1 and those of the composites from 0.7 to 0.9. The results were very consistent between study protocols.

Thus, in comparison to individual endpoints, composite analyses of OA clinical endpoints do not increase precision to discriminate active treatment from placebo, these authors conclude.
J Rheumatol 2001;28:2700-4. "Precision of Composite Measures of Osteoarthritis Efficacy in Comparison to That of Individual Endpoints"

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