Impact of Limited Health Literacy on Patient‐Reported Outcomes in Systemic Lupus Erythematosus

Objective Health disparities in patient‐reported outcomes by income and education are well documented; however, the impact of health literacy on patient‐reported outcomes has received less attention. We examined independent effects of income, education, and health literacy on patient‐reported outcomes in systemic lupus erythematosus (SLE). Methods Data from the California Lupus Epidemiology Study (n = 323 participants) were used. Health literacy was assessed with a validated 3‐item measure (ability to understand written information, reliance on others to understand written information, confidence in completing written forms). Patient‐reported outcomes were administered by interview in English, Spanish, Cantonese, or Mandarin. Generic and disease‐specific patient‐reported outcomes were examined using the following: 10 Patient‐Reported Outcomes Measurement Information System (PROMIS) short forms; the 8 Short Form 36 (SF‐36) health survey subscales; and 3 patient‐reported SLE disease activity and damage measures. We conducted 2 sets of multivariable analyses: the first examined education, income, or health literacy individually; the second included all 3 simultaneously. All multivariable models included age, sex, race/ethnicity, language, disease duration, and physician‐assessed disease activity and damage. Results More than one‐third of participants (38%) had limited health literacy (LHL), including >25% with greater than high school education. In multivariable analyses simultaneously considering education, income, and health literacy, LHL was associated with significantly worse scores on all patient‐reported outcomes except disease damage. In contrast, disparities by income were seen in only 3 PROMIS scales, 3 SF‐36 subscales, and 1 disease activity measure. No disparities by education level were noted. Conclusion We found significantly worse patient‐reported outcome scores among individuals with LHL, even after controlling for disease activity and damage. Whether disparities are due to actual differences in health or measurement issues requires further study.