For the purposes of meta-analysis and network meta-analysis, the use of standard outcome measures is ideal. In OA research, the WOMAC was developed as an OA-specific measure of disability. It includes a pain subscale. In 1994 a consensus meeting recommended the use of WOMAC as a primary measure of efficacy in OA. In the context of a review of the efficacy of physical interventions for the relief of the pain of OA of the knee, we investigated the use of WOMAC.
A systematic review (December 2009-January 2010) identified trials that used the WOMAC outcome. These were investigated for correct use and clear reporting of the WOMAC pain subscale and the WOMAC index.
The WOMAC pain subscale was used in 45% of the 134 trials. Reporting of the exact method of administering the WOMAC pain subscale was poor in many cases: in 53% of trials the reporting of the type of WOMAC scale used was inadequate; the score range was reported ambiguously in 38% of trials, with a further 10% being completely unclear. Similar less than optimal reporting of the WOMAC index was found.
Poor reporting of both the WOMAC pain subscale and the WOMAC index resulted in significant uncertainty in the interpretation of the results of individual trials and limited their contribution to evidence synthesis. Improved adherence with the standard use of the WOMAC scoring system, with clear reporting of it in trials of OA of the knee should be encouraged.