Background/Purpose: Rheumatoid Arthritis (RA) patients who are anti-citrullinated peptide antibody (ACPA) positive are prone to more severe structural damage, radiographic progression and inferior response to therapy. It’s known that ACPA positive patients are associated with additional cost as compared to ACPA negative. It’s unclear however if the incremental cost associated with ACPA-positive RA varies by the care pathway they follow. The study objective was to evaluate the incremental costs associated with ACPA-positivity in different groups of RA management pathways.

Methods: A retrospective cohort study was conducted in RA patients identified using electronic medical records from the Kaiser Permanente Southern California health plan. Between 01/01/2007 and 12/31/2015, we identified patients aged ≥18 years who had ≥2 RA diagnoses within a 12-month period, a disease-modifying antirheumatic drug (DMARD) prescription and laboratory test for ACPA. Patients were followed for two years post diagnosis. Latent class analysis (LCA) method was applied to identify ≥2 heterogeneous RA management patterns. RA-specific healthcare utilization during the first-year follow-up was used to identify the latent classes. During the second year of follow-up, we estimated total RA-specific expenditures associated with hospital stays; outpatient visits; office visits; pharmacy; laboratory and radiology utilization. A generalized linear model, evaluating the difference in expenditure between ACPA positive vs negative patients was specified with an effect modification term for latent class and adjusting for socio-demographics and comorbidities.

Results: We identified 2842 incident RA patients, mean age 56 years and majority female 76%. LCA indicated five latent classes representing mutually exclusive pathways of patient management and care (Table 1). Adjusted total RA-specific expenditure ranged from $1167 in class one to $21008 in class five for ACPA-positive patients (Table 2). The difference between ACPA positive and negative patients in the least severe class (Class 1) was statistically non-significant difference of $214. However, in class two and above, this difference was statistically significant and progressively increasing. In patients characterized by high disease activity and high progression (Class 5) the expenditure difference was 27-fold higher ($5708) as compared to Class 1 (Table 2).  

Conclusion: Across the 5 distinct care pathways identified by LCA, based on the management and care of RA patients, the magnitude of the incremental cost associated with ACPA-positivity varied.