Background/Purpose: Herpes zoster (HZ) is a disease caused by the reactivation of the varicella-zoster virus in previously infected individuals and is characterized by a painful dermatomal rash. The incidence of HZ is higher in patients with RA than in the general adult population. With the increased incidence of HZ in patients with RA, it is important to understand the clinical and economic burden associated with HZ in this population. This study sought to estimate the additional burden posed by HZ in patients with RA.

Methods: This was a retrospective cohort study using a large administrative claims database with commercial and Medicare Advantage with Part D data from October 2015 to February 2020. Patients with HZ and RA were identified using International Classification of Diseases and Related Health Problems (10^th edition) diagnosis codes in medical claims. The first HZ diagnosis was the index date (Fig. 1a). A confirmed RA diagnosis was required as defined by ≥2 RA diagnoses on medical claims ≥6 weeks apart and ≥3 months of continuous DMARD treatment in the year following the first RA diagnosis. A comparator cohort was identified based on the same criteria for RA but was required not to have HZ at any time. Index date in this cohort was randomly selected based on the distribution of time from the beginning of continuous enrolment to index date in the HZ and RA cohort (Fig. 1b). All patients were required to have at least 12 months of continuous medical and pharmacy benefit enrollment before (baseline) and after index (follow-up). Baseline demographic, clinical, and cost information were reported. Outcomes included healthcare resource use (HCRU) and total, medical (including by setting) and pharmacy costs during the 12-month follow-up. Generalized linear models were used to estimate differences in outcomes between cohorts, adjusting for patients’ propensity scores as a covariate in the model and adjusting for key baseline variables as additional covariates.

Results: The study included 1,866 and 38,846 patients in the RA and HZ and RA only cohorts, respectively. Mean ± standard deviation (SD) age in the RA and HZ cohort was 68 ± 12 vs 66 ± 13 in the RA only cohort. Most patients in both cohorts were females. Higher proportions of patients in the RA and HZ cohort used JAK inhibitors or systemic steroids at index compared to the RA only cohort (Tab. 1). Baseline mean ± SD total costs were $52,625 ± 67,774 and $46,332 ± 65,480 in the RA and HZ and RA only cohorts, respectively. During the 12-month follow-up, hospitalizations and emergency department (ED) visits occurred more often in the RA and HZ cohort than in the RA only cohort with an adjusted incidence rate ratio (95% confidence interval [CI]) of 1.16 (1.04, 1.30) for hospitalizations and 1.34 (1.21, 1.47) for ED visits. Medical costs were higher in the RA and HZ cohort during the 12-month follow-up compared to the RA only cohort, with an adjusted cost difference (95% CI) of $3,428 (446, 6,781) (Tab. 2).

Conclusion: Patients with RA and HZ had higher HCRU and medical costs than patients with RA only in the year following an HZ diagnosis after adjusting for baseline difference between cohorts. These findings provide evidence of the added burden of HZ in patients with RA and the need for interventions to reduce this burden.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-and-economic-burden-of-herpes-zoster-in-patients-with-rheumatoid-arthritis-a-retrospective-cohort-study-using-administrative-claims/