The ShortMAC: Minimum important change of a reduced version of the WOMAC Osteoarthritis Index

WOMAC is a questionnaire widely used by health professionals to evaluate the condition of Osteoarthritis patient. These is need to update this index due to its low efficacy and complication. Therefore, in this study, a new version i.e shortMAC is described by the author which showed greater efficiency for use in clinical trials and reduced patient burden.

A 12-item reduced-item version of the Western Ontario and McMaster (WOMAC), patient-reported osteoarthritis index, a condition-specific, has been obtained, published and verified. The minimum important change (MIC) of the ShortMAC has not been described or matched with the traditional 24-item WOMAC. This study was conducted to examine the MIC of the 12-item ShortMAC and the traditional 24-item WOMAC over three levels of patient-perceived global change.

A total of 206 consecutive participants with hip or knee osteoarthritis were evaluated at the first visit and following nine weeks of usual medical care or physical therapy. The assessment of the Global Rating of Change (GROC) instrument done at the 9-week visit. Receiver operating characteristic curve strategy was applied to measure MIC, and GROC defined the ShortMAC and the traditional WOMAC over three levels of patient-perceived change; small, medium, and large.

The MIC for the ShortMAC and traditional WOMAC was 7.9 and 9.8 point, 8.4 and 9.8 points, and 12.1 and 10.1 points for small, medium, and large change, respectively. The MIC of the function and pain subscales are also listed for small, medium, and large change.

The lower point estimates for MIC of the ShortMAC showed higher efficacy for use in clinical trials and decreased the patient burden than the traditional WOMAC.