The Impact of Social Economic Status on Biologic Treatment Disparity in Inflammatory Bowel Disease

OBJECTIVES: Biologics and biosimilars have gained approval to induce clinical remissions in ulcerative colitis (UC) and Crohn's disease (CD), both forms of inflammatory bowel diseases (IBD). In the United States, obtaining access to biologics typically requires prior authorization and copayment. This study seeks to evaluate the influence of socioeconomic status (SES) on the rate of biologic treatment as an indicator of patient access disparity in UC and CD, respectively.

METHODS: UC and CD patients were identified using ICD-10 codes and medical history from January 2016 to June 2022. A HIPAA-compliant US representative administrative database with three-digit zip codes (ZC) was utilized. SES was defined by the Social Viability Index (SVI) from the Agency for Healthcare Research and Quality (AHRQ) Social Determinant of Health database. A connection algorithm between these databases was developed using the 5-digit ZC and Federal Information Processing System link from the US Zip Code Database. Mean SVI across 5-digit ZC was derived for each corresponding 3-digit ZC. Sensitivity analyses were conducted, selecting only homogeneous 3-digit ZC, i.e. SVI differences within 0.1 across 5-digit ZC. Descriptive analysis of biologic treatment rate (Biorate) by SVI quartile groups (SVIgrp) and logistic regression models controlling for gender and age were implemented using SAS Studio.

RESULTS:

Overall, 497,957 UC patients with non-missing ZC received treatments during study period. UC Biorate was 8.7%, 8.9%, 10.2%, and 10.4% by SVIgrp (from lowest to highest quartile). SVIgrp was a statistically significant factor (P<0.001) impacting Biorate after adjusting for gender and age. Consistent results were achieved in sensitivity analyses using homogeneous 3-digit ZC. Annual differences across SVIgrp were slightly different from 2016 to 2022. Same analyses were conducted in CD, and similar SVIgrp impacts to Biorate were found also.

CONCLUSIONS: SVI difference was associated with the varying level of usage of biologic treatments in IBD.