Perceived and Objective Physical Function in 2 United States Population-Based Cohorts of Adults With Systemic Lupus Erythematosus

Objective We leveraged data from 2 population-based systemic lupus erythematosus (SLE) cohorts (Approaches to Positive, Patient-Centered Experiences of Aging With Lupus [APPEAL] and the California Lupus Epidemiology Study [CLUES]) to provide estimates of, and identify factors associated with, perceived and objective physical function (PF) and their discordance.

Methods Perceived PF (Patient-Reported Outcomes Measurement Information System [PROMIS] 12a/10a [APPEAL/CLUES]; t-scores [mean 50, SD 10]) and objective PF (Short Physical Performance Battery [SPPB]; score range 0-12) were examined by cohort and participant characteristics (higher scores indicated better function). We assessed factors associated with discordance between scores (≥ 2 quartile difference) using multinomial logistic regression.

Results APPEAL (N = 446; 81.4% Black) vs CLUES (N = 173; 41% Asian, 27.7% White, 23.1% Hispanic) participants had lower perceived PF (PROMIS t-scores, 41.5 vs 47.9) and objective PF (SPPB scores, 9.0 vs 9.4). There was no difference after adjustment for disease activity and cumulative disease damage. Factors associated with lower perceived PF and objective PF across cohorts included oldest vs youngest age (t-scores, 40.8 vs 47.4; SPPB scores, 8.9 vs 9.6), Black vs White race (t-scores, 40.8 vs 45.6; SPPB scores, 8.9 vs 9.7), and higher vs lower disease activity (t-scores, 38.1 vs 48.4; SPPB scores, 8.7 vs 9.6). Overall, 22.4% of participants had discordant scores; older age and higher disease activity were independently associated with lower risk of overestimating PF (objective score < perceived score).

Conclusion Our findings show that perceived and objective PF can vary considerably across SLE populations and patient characteristics. Perceived PF may not always reflect objective PF in SLE populations.