Meaningful Within-Patient Changes Established for WOMAC Domains in Osteoarthritis

The Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index can measure meaningful within-patient changes (MWPCs) in patients with moderate to severe knee and hip osteoarthritis (OA), according to study results published in The Journal of Rheumatology.

In recent years, guidance from the US Food and Drug Administration (FDA) on measuring outcomes in drug development clinical trials has placed a greater emphasis on defining MWPC. The FDA recommends using an external anchor measure to define MWPC of an outcome measure at the individual level.

In the current study, the researchers evaluated the use of WOMAC, a disease-specific measure of OA, anchored to the patient global assessment of OA, to estimate MWPC in patients receiving treatment with tanezumab for OA of the hip and knee.

The researchers analyzed data from 3 phase 3 clinical trials (ClinicalTrials.gov Identifiers: NCT02697773, NCT02709486, and NCT02528188) evaluating the safety and efficacy of tanezumab in patients with moderate to severe knee and hip OA.

Patients enrolled in the study completed the WOMAC and patient global assessment of OA (PGA-OA) at regular timepoints.

A repeated-measures longitudinal model was used to calculate MWPCs using change in WOMAC domain scores as the outcome and change in PGA-OA as the anchor. 

In all 3 studies (n=688, n=844, and n=2948), a linear relationship between changes in WOMAC domains and changes in PGA-OA was observed, with excellent agreement between 2 of the studies and good agreement with the third. The overall MWPC that corresponded to a 1-category change in the PGA-OA was 0.84 to 1.16 (based on the 0-10 rating scale) and from 12.50% to 16.23%. For a 2-category change in the PGA-OA, the MWPC was 1.68 to 2.31 and from 25.01% to 32.46%.

A limitation of the study included the use of only 1 anchor measure.

The researchers concluded, “These data may aid the interpretation of clinical trials in patients with OA of the hip or knee by defining the meaningful response to treatment in this patient population. Defining MWPC for patients with OA may also be valuable to health­care professionals, as a means to assess the effect of their inter­ventions. Further work should examine the most appropriate anchor measures and the best methods to determine MWPC.”

Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

Reference

Conaghan PG, Dworkin RH, Schnitzer TJ, et al. WOMAC meaningful within-patient change: results from 3 studies of tanezumab in patients with moderate-to-severe osteoarthritis of the hip or knee. J Rheumatol. Published online May 1, 2022. doi:10.3899/jrheum.210543