Background/Purpose: Anti-cyclic citrullinated peptide (CCP) antibody is a marker used in the diagnosis of RA, and it may be useful in identifying patients who are likely to have severe disease activity and joint damage.¹ This study compared RA-related healthcare utilization between patients with RA who are anti-CCP antibody positive versus negative.

Methods: Using electronic medical records from the Henry Ford Health System (HFHS), patients newly diagnosed with RA (International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis code 714.0x) were identified between 1/1/09 and 12/31/14. The first RA diagnosis date was the index date. Patients were required to have 12 months of continuous activity in the HFHS (6 months pre- and 6 months post-index). Baseline anti-CCP test was used to categorize patients as positive or negative for anti-CCP antibodies. RA-related healthcare utilization evaluated in the post-index period included: laboratory testing (RF, CRP and ESR), outpatient visits, emergency room visits and hospitalizations. Statistical comparisons between the cohorts were conducted with chi-square tests for categorical variables and t-tests for continuous variables.

Results: The analysis included 103 anti-CCP-negative and 248 anti-CCP-positive patients with RA. Mean age was 58.5 years and 78.9% were female. The anti-CCP-positive cohort had a higher proportion of Black patients than the anti-CCP-negative cohort (44.4 vs 34.0%, p<0.0001). Joint pain was present in 39.3% of patients. Inflammatory back pain was higher in the anti-CCP-negative compared with the anti-CCP-positive cohort (14.6 vs 7.7%, p=0.0465). During follow-up, compared with the anti-CCP-positive cohort, a higher proportion of the anti-CCP-negative cohort was tested for RF (41.7 vs 19.4%, p<0.0001), CRP (71.8 vs 58.5%, p=0.0185) and ESR (66.0 vs 52.0%, p=0.0161). Among those tested, higher proportions of the anti-CCP-positive cohort than the anti-CCP-negative cohort had positive test results (RF: 83.3 vs 25.6%, p<0.0001; CRP: 68.3 vs 58.1%, p=0.1361; and ESR: 82.2 vs 60.3%, p<0.0001); significance was not reached for CRP. RA-related healthcare utilization occurred mainly in the outpatient setting. The proportion of patients with any outpatient physician office visit and the mean (SD) number of visits were highest in the anti-CCP-positive cohort compared with the anti-CCP-negative cohort (96.8 vs 88.3%, p=0.0019 and 5.3 [3.1] vs 3.6 [2.9)], p<0.0001). Most outpatient visits were to a rheumatologist, and the proportion of patients with a visit and mean (SD) number of visits were higher in the anti-CCP-positive compared with the anti-CCP-negative cohort (93.5 vs 73.8%, p<0.0001 and 4.4 [2.5] vs 3.3 [2.3], p=0.0003). Other healthcare utilization in outpatient and other settings was similar between the two cohorts.

Conclusion: Patients with RA who are anti-CCP positive had laboratory results indicative of higher inflammation and disease activity, which likely led to the higher healthcare utilization in the outpatient office setting. Future studies may evaluate differences in treatment outcomes and costs by anti-CCP serostatus. 1. Niewold TB, et al. Q J Med 2007;100:193–201.