Correlation of psoriasis activity with socioeconomic status: cross-sectional analysis of patients enrolled in the Psoriasis Longitudinal Assessment and Registry (PSOLAR)

DEAR EDITOR, The interdependence between socioeconomic status and disease control in patients with severe psoriasis is not well understood. To assess whether worse disease control among patients with historically severe psoriasis correlated with negative socioeconomic status, we conducted a cross‐sectional analysis using the Psoriasis Longitudinal Assessment and Registry (PSOLAR), a large, observational study of patients with psoriasis receiving, or eligible to receive, conventional systemic or biological therapies.1 Patients living in the U.S.A. with historically severe psoriasis [i.e. a Physician's Global Assessment (PGA) score of 4/5 and/or a per cent body surface area (%BSA) > 10%] before enrolment were grouped based on predefined criteria for psoriasis control at baseline:2 3 (i) well‐controlled (group 1, PGA, 0/1 and/or %BSA ≤ 3); (ii) moderately controlled (group 2, PGA, 2 and/or %BSA > 3 to ≤ 10); (iii) poorly controlled (group 3, PGA, 3 and/or %BSA > 10 to ≤ 20); and (iv) very poorly controlled (group 4, PGA, 4/5 and/or %BSA > 20). The relationship between psoriasis control and socioeconomic status at enrolment was evaluated based on descriptive parameters, and logistic regression analyses were performed to examine the correlation between disease control (groups 2, 3, 4 vs. group 1) and socioeconomic status as measured by income bracket (annual household income bracket of < $41 000 or ≥ $41 000), health insurance type [private vs. public (Medicaid/Medicare) or none] and education level (≤ high school degree vs. > high school degree). Missing data for socioeconomic variables were not imputed. A total of 4037 patients met criteria for study inclusion and were categorized as having psoriasis that was well‐controlled (group 1; n = 899), moderately controlled (group 2; n = 962), poorly controlled (group 3; n = 964) or very poorly controlled (group 4; n = 1212) at enrolment. At enrolment, group 4 had the highest proportions of patients who were nonwhite, weighted more or were biologic‐naïve. The proportions of patients with worse socioeconomic status was lowest in group 1 and highest in group 4, including lower income (ranging from 19·4% to 27·6%), public or no insurance (15·5% to 23·1%) and less education (31·6% to 42·2%). Disease severity based on mean %BSA was higher in group 4 than in groups 1, 2 and 3, respectively, at historical peak activity (47·2% vs. 32·9%, 34·7% and 29·0%) and enrolment (40·5% vs. 1·0%, 5·5% and 12·5%). This indicated that group 4 may represent a biologically different group and, therefore, post hoc analyses were conducted to compare group 4 with combined groups 1–3 and groups 3/4 with groups 1/2. Results showed that, although no independent associations were found between disease control and either income bracket or insurance type at registry entry, the positive association between poor psoriasis control and lower education was strong (Fig. 1). Across all comparisons, patients with poor or very poor control of psoriasis were significantly more likely than those with well‐controlled or moderately controlled disease to have finished their education at the high‐school level. Patients included in this analysis were diagnosed with psoriasis in their thirties on average, indicating the diagnosis itself was not likely to have had an impact on the educational level achieved by the patient. Rather, this finding may be attributable, at least in part, to the fact that patients with a higher education may be more willing or better able to seek better treatment for their condition. The literature regarding the relationship between psoriasis control and education level is limited. However, multivariate analyses in a cross‐sectional study of patients with psoriasis at a first dermatology consultation corroborate our results showing low educational level is associated with more severe disease.4 Adjusted odds ratios and 95% confidence intervals derived from logistic regression analysesa of comparisons of socioeconomic outcomes (i.e. income bracket, insurance, type and education level) across disease control groups: group 1 (well‐controlled psoriasis); group 2 (moderately controlled psoriasis); group 3 (poorly controlled psoriasis) and group 4 (very poorly controlled psoriasis). aPredefined covariates (including age, gender, ethnicity, duration of psoriasis, obesity status, prior biologic use, health‐related quality of life (Dermatology Life Quality Index), income bracket, insurance type and education level) were examined in a univariate logistic regression analysis; if the P‐value was ≤ 0·20, the covariate was included in the multivariate model. bAn odds ratio > 1 reflects an association with the negative socioeconomic factor (i.e. income < $41 000/year, public/no insurance, or high school or less education). cOnly those employed full time were included in the income analysis. dHealth insurance type was defined by the answer to the request to ‘check all forms/categories of insurance/medical coverage: Medicare, Medicaid, private, or none’. Patients were categorized as ‘yes’ or ‘no’ for Medicaid, Medicare under age 65 or no insurance status. The strengths of this analysis are the large population and comprehensive collection of both level of psoriasis control at enrolment and information on past disease severity data. One limitation is the cross‐sectional design, with independent (disease severity) and dependent variables collected at the same time point; therefore, we were not able to establish causality between them. Other limitations regarding the dataset – including a geographic bias (U.S.A. only) and inclusion of only patients who were employed full‐time – should also be considered when interpreting the results. Particularly for income, a large amount of missing data was not imputed in our analysis; for the other outcomes, data capture was more complete and sensitivity analyses imputing missing data confirmed the conclusion. Although data regarding some potential confounding factors may not be readily available for this analysis, educational interventions for patients with psoriasis regarding health literacy, navigation of the healthcare system and equitable access to care may be worth exploring. Determination of the best end point surrogates and best methods for quantifying them for a more comprehensive evaluation of the effect of treatment on socioeconomic status will be important future work. Funding sources: This study (clinicaltrials.gov: NCT00508547) was supported by Janssen Scientific Affairs, LLC, Horsham, PA, U.S.A. Conflicts of interest: A.B.K. has received grants/research funding and honoraria as a consultant and investigator for AbbVie, Dermira, Janssen, Novartis and Regeneron, received honoraria as a consultant for Eli Lilly and UCB and received fellowship programme funding as an investigator from Janssen. M.A. has served as consultant to, or paid speaker for, clinical trials sponsored by companies that manufacture drugs used for the treatment of psoriasis, including AbbVie, Almirall, Amgen, Biogen, Boehringer Ingelheim, Celgene, Centocor, Eli Lilly, GSK, Hexal, Janssen‐Cilag, Leo, Medac, Merck, MSD, Mundipharma, Novartis, Pfizer, Sandoz, Stiefel, UCB and Xenoport. K.B.G. has received research support and honoraria from AbbVie, Amgen, Boehringer Ingleheim, Celgene, Eli Lilly, Janssen and Novartis and honoraria from Dermira and Sun Pharma. G.G.K. has received fees as a consultant and lecturer for AbbVie, Amgen, Boehringer Ingleheim, Janssen, Lilly, Novartis, Pfizer and UCB; in the past 12 months, he has received lecture fees from AbbVie, Amgen, Janssen and Novartis; he has also received partial stipend support for a clinical research fellowship from AbbVie. D.P. has served as a consultant and received honoraria from Abbott, Amgen, Astellas, Bickel Biotechnology, Celgene, Dermira, DUSA, LEO, MelaSciences, Novartis, Proctor & Gamble and Valeant. He has also participated in advisory boards and received honoraria from Galderma, Genentech, Janssen‐Ortho, Medicis, Ortho Dermatologics, Pfizer and Stiefel. In addition, D.P. served as an investigator and received research grants from Abbott, Amgen, Astellas, Asubio, Basliea, Celgene, Dow Pharmaceutical Sciences, Eli Lilly, Galderma, Graceway, Intendis, Johnson & Johnson, LEO, Novartis, Novo Nordisk, Ortho Dermatologics, Peplin, Pfizer, Photocure ASA, Stiefel and Valeant. S.F., K.G., S.C., S.L., N.L. and B.S. are employees of, and own stock in, Johnson & Johnson (which owns Janssen the study sponsor). R.L. provides statistical services to Janssen Research & Development, LLC. L.G. has been a consultant, speaker and participated in clinical research with Amgen, AbbVie, Boehringer Ingelheim, Celgene, Eli Lilly, Janssen, Merck Frosst, Novartis and Pfizer.

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