Discriminative validity of the EQ-5D-5 L and SF-12 in older adults with arthritis

Background: The EQ-5D-5 L and the SF-12 are the most commonly used generic measures of health-related quality of life among people with arthritis. However, there is little evidence on the extent to which the individual dimensions and domains of these instruments perform among this population. The objective was to examine the discriminative validity of the EQ-5D-5 L and the SF-12 version 2 (and SF-6D) in capturing the burden of arthritis on health-related quality of life in older adults. Methods: Cross-sectional data from the Alberta Retired Teachers Association survey were used. A known-groups approach, with a-priori hypotheses, was used to examine the discriminative validity of the domain and summary scores of the EQ-5D-5 L and the SF-12 version 2 (and SF-6D). Groups were defined based on self-reported of arthritis, chronic pain level, presence and number of comorbidities, and self-reported health status. Results: Mean age of respondents (N = 2844) was 68.6 (standard deviation [SD] 5.9) years; 54.8% were female, with mean body mass index (BMI) of 27.2 kg/m(2) (SD 4.8), and 36.6% reported having arthritis. The overall mean EQ-5D-5 L index score was 0.86 (SD 0.11) and that of SF-6D was 0.79 (SD 0.13). Participants with arthritis had lower EQ-5D-5 L index score (0.83, SD 0.13) and SF-6D index score (0.75, SD 0.13) compared to those without arthritis (0.88, SD 0.09 and 0.81, SD 0.12, respectively). EQ-5D-5 L and SF-6D index scores demonstrated moderate discriminative validity with a moderate effect size (0.5). Related dimensions and domains between the EQ-5D-5 L and SF-12 (e.g., mobility with physical functioning score, pain/discomfort with bodily pain and anxiety/depression with mental health) were moderately to strongly correlated (r = 0.6-0.7). Both instruments could not adequately discriminate between participants with moderate and severe chronic pain of 6-month duration. Conclusion: Overall, the EQ-5D-5 L pain/discomfort and mobility dimensions, and the SF-12 bodily pain scale had moderate discriminative ability among older adults with arthritis. However, both instruments had limited discriminative ability for chronic pain. The importance and nature of chronic pain assessment in a given application need to be considered when choosing any of these instruments for measuring health-related quality of life in this patient population.