Anti-cyclic citrullinated peptide antibody (ACPA) has excellent specificity and prognostic value in patients with early rheumatoid arthritis (RA). The American College of Rheumatology included ACPA in their 2010 classification criteria for RA, but we hypothesize that primary care physicians (PCPs) underuse ACPA, even when clinical suspicion for RA is high. We aimed to describe their use of diagnostic testing in patients who were referred to a rheumatologist and eventually diagnosed as having RA.
In this retrospective cohort study, a systematic abstraction tool was used to review the medical records of patients seen between January 1, 2010 and June 15, 2014 in two rheumatology clinics: one private practice and one community health center associated with an academic medical center. For purposes of hypothesis generation, we compared the characteristics of patients with and without testing using unpaired 
We identified 173 patients with RA referred from 141 different PCPs: 82.7% were women with a mean ± standard deviation age of 55.5 ± 18.6 years. ACPA and rheumatoid factor were ordered in 28.9% (95% confidence interval 22.6-36.2) and 41.0% (95% confidence interval 33.9-48.6) of patients, respectively. Imaging was underused. Almost half (45.7%, or 37/81) of the patients with documented symptom duration had a delay of at least 1 year before referral; however, ACPA utilization was not associated with the delay to treatment initiation.
Most PCPs failed to order diagnostic tests for RA before referring a patient with polyarthritis who eventually received a diagnosis of RA. We also observed delays in diagnosis, with half of the patients waiting >1 year from symptom onset to diagnosis. These findings suggest educational efforts for PCPs should focus on emphasizing earlier diagnostic workups, especially ACPA, in patients suspected to have RA.