Comparison of Methods to Estimate Disease-Related Cost and Healthcare Resource Utilization for Autoimmune Diseases in Administrative Claims Databases

Background: Establishing disease-related cost and/or healthcare resource utilization (HCRU) is an important aspect of health outcomes research, particularly when considering the cost offset of novel treatments. However, few studies have compared methodologies used to assess disease-related cost/HCRU. Methods: Data from the United States IBM (R) MarketScan (R) Research Databases were used to compare four different methods of calculating disease-related cost and HCRU in patients with rheumatoid arthritis (RA). The analysis was repeated, in part, for patients with ulcerative colitis (UC) to explore the generalizability of findings to a second autoimmune disease. Four methods of disease-related cost/HCRU attribution were selected following a literature search for potential methods: Method 1, claim-wide cost/HCRU attribution based on claim-listed diagnosis codes and a predetermined disease-related medication list (pharmacy claims only); Method 2, line-item cost/HCRU attribution based on procedures/medications more likely to occur in disease cases than in matched controls at two likelihood ratio cutoffs (1.5x and 3.5x); Method 3, disease-related cost/HCRU calculated as the difference in total average cost/HCRU between cases and matched controls; Method 4, line-item cost/HCRU attribution based on clinician manual determination of procedures/medications related to the disease. Results and conclusion: Overall, 24,373 patients with RA and 9665 with UC were included. Average total cost during 2015 was $US28,750 per patient with RA and $US20,480 per patient with UC. Disease-related cost and HCRU for RA calculated using Method 4 were most closely approximated by Methods 1 and 2 (3.5x), with Method 2 (3.5x) the closest approximation. However, in certain research scenarios, the simplest method compared in this analysis, Method 1, may provide an adequate approximation of disease-related cost and HCRU. Although Method 4 was not executed in the UC analysis because of its labor-intensive nature, similar patterns of disease-related cost and HCRU were observed for Methods 1-3 in patients with UC and RA.