Association Between the Single Assessment Numeric Evaluation and the Western Ontario and McMaster Universities Osteoarthritis Index

Abstract

Context:  Patient-reported outcomes (PROs) evaluate how patients describe symptoms as well as level of physical function or quality of life. The Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index is one of the most common PROs used to assess disability in patients with knee osteoarthritis (OA), yet the Single Assessment Numeric Evaluation (SANE) is a single-question instrument that may improve the efficiency associated with the measurement of patient function. Objective:  To determine the associations between (1) SANEFunction and the physical dysfunction subsection of the WOMAC index (WOMACDysfunction) before rehabilitation and after a 4-week therapeutic exercise intervention as well as (2) the percentage change in SANEFunction and WOMACDysfunction in people with knee OA after 4 weeks of therapeutic exercise. Design:  Cross-sectional study. Setting:  Research laboratory. Patients or Other Participants:  Thirty-six participants (15 men, 21 women) with radiographic knee OA. Intervention(s):  Participants completed 12 sessions (over a 4-week period) of therapeutic exercise to strengthen the lower extremity. Main Outcome Measure(s):  The SANEFunction and WOMACDysfunction (WOMACDysfunction normalized to 100%) scores were collected before and after the 4-week intervention. Percentage change scores over the 4-week intervention were calculated for both measures. Results:  Participants with a higher SANEFunction score demonstrated a lower WOMACDysfunction score at baseline (rs = –0.44, P = .007) and at the 4-week time point (rs = –0.69, P < .001). There was a nonsignificant and weak association between the changes in the SANEFunction and WOMACDysfunction scores over the 4 weeks of therapeutic exercise (rs = –0.17, P < .43). Conclusions:  The SANEFunction and WOMACDysfunction scores demonstrated moderate to weak associations before and after a 4-week exercise program, respectively, whereas the changes in SANEFunction and WOMACDysfunction scores were not associated. These PROs may be measuring different aspects of self-reported function and therefore should not be used interchangeably to determine a therapeutic response.