s215 cost for procedures/medications occurring at increased frequency in the disease cohorts versus controls (1.5x and 3.5x were both tested). Method 3 used the difference in total cost between disease cohorts and matched controls. Method 4 (RA only) served as our internal standard method and utilized a separate stand-alone clinician review of codes received by the RA cohort. Outpatient/pharmacy claims flagged as RA-related were included in the Method 4 analysis. Results: 24,373 RA patients and 9,665 UC patients were included. Average total cost was $28,750 per RA patient and $20,480 per UC patient. RA-related cost as a percent of total cost: method 1, 48%; method 2 (1.5x), 56%; method 2 (3.5x), 44%; method 3, 73%; method 4, 44%. UC-related cost as a percent of total cost: method 1, 50%; method 2 (1.5x), 50%; method 2 (3.5x), 42%; method 3, 70%. Percent disease-related cost attributed to each cost component (emergency room, inpatient, outpatient, pharmacy) tracked similarly comparing RA to UC within each method 1-3. In RA, our internal standard method 4 was closest in disease-related cost and cost component attribution to method 2 (3.5x). ConClusions: Method 2 (3.5x) is our proposed method for calculating disease-related cost.