Healthcare Resource Utilization and Costs

The baseline period was followed by the “observation period”, defined as the period between the index date and the end of data availability, lasting a minimum of 12 months. During the observation period, all-cause HRU and costs were measured for the RA+/HZ+ and RA+/HZ− cohorts over the first month (month 1), quarter (quarter 1), and year (year 1).

HRU included the frequency of inpatient stays, emergency department visits, outpatient visits, and services and encounters in other settings. HRU outcomes for month 1, quarter 1, and year 1 were reported as the mean number of HRU events per patient for the respective time horizons. Incidence rates (IRs) were calculated by dividing the number of encounters in the observation period by the patient-time observed. While these are referred to as IRs in the analysis, they represent count or frequency of events rather than singular incident events.

Healthcare costs included medical and pharmacy costs, which were adjusted to 2020 US dollars (USD) using the medical care component of the Consumer Price Index [22]. Medical costs were measured overall and for specific settings (inpatient, emergency department, outpatient, and other settings). Medical costs also encompassed medications administered in a medical setting coded with a procedure code (e.g., biologics for RA given by intravenous infusion), which were categorized by the setting in which the medication was administered and billed. Pharmacy costs were derived from the costs in pharmacy claims data covered under the patients’ pharmacy benefit scheme. Total healthcare costs were measured as the sum of medical and pharmacy costs. All costs represented an estimate of the allowed amount, as opposed to paid or billed amounts.