OBJECTIVES: To examine the discriminative validity of the EQ-5D-5L and the SF-12 v.2 in capturing the burden of arthritis on health-related quality of life (HRQL) of older adults.

METHODS: Cross-sectional data from the Alberta Retired Teachers Association survey were used. Known-groups approach with a-priori hypotheses was used to examine the discriminative validity of theEQ-5D-5L dimension, VAS and index scores, and SF-12 v.2 domain, summary (PCS, MCS) and index scores (SF-6D). Groups were identified based on self-reported presence 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 (SD 5.9) years; 54.8% were female, with mean body mass index (BMI) of 27.2 kg/m(SD 4.8) and 36.6% reported having arthritis. The overall mean EQ-5D-5L index score was 0.86 (SD 0.11) and mean SF-6D score was 0.79 (SD 0.13). Participants with arthritis had lower EQ-5D-5L index score (0.83, SD 0.13) and SF-6D 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-5L index score and SF-6D demonstrated moderate discriminative validity based on known-group analyses (effect sizes range: 0.2-0.6). Related dimensions and domains between the EQ-5D-5L and SF-12 were moderately to strongly correlated (r=0.6-0.7). Most importantly, both instruments could not adequately discriminate between patients with moderate and severe chronic pain of 6-month duration, whereby, patients with moderate chronic pain had lower index scores on both instruments compared to those with severe chronic pain.

CONCLUSIONS: Overall, the EQ-5D-5L and SF-12 v.2 demonstrated moderate discriminative validity among older adults with arthritis. However, the discriminative validity of both instruments was limited with respect to chronic pain; a very important feature of arthritis. The nature of pain (acute vs. chronic) need to be considered when choosing any of these instruments for measuring HRQL in this clinical population.