Double positivity for rheumatoid factor and anti-CCP autoantibodies: improving referral from primary care of patients suspected of having rheumatoid arthritis.

Background: Rheumatoid arthritis (RA) is a chronic progressive autoimmune inflammatory disease with significant morbidity and mortality. The course of the disease can be modified if diagnosis is early and treatment appropriate.

Aim: In this study, we aimed to evaluate a new strategy for early identification of RA patients in primary care settings (the 'diagnostic bottleneck') based on serological biomarkers and to manage inappropriate rheumatoid factor (RF) laboratory test requests.

Method: A two-arm study was carried out. The first arm corresponded to a retrospective observational descriptive study of patients referred for RF testing from primary care using the current laboratory workflow. The second arm included the following prospective interventions: cancelation of RF requests corresponding to patients with previous negative results for RF over a one-year period; and automatic reflex testing antibodies against cyclic citrullinated proteins (anti-CCP) for patients displaying RF values >30 IU/ml. Outcomes from both arms were then compared.

Findings: As double positivity for RF and anti-CCP notably increases the positive likelihood ratio of RA. The intervention enabled a reduction of 2813 tests in 22 months. Moreover, the frequency of unnecessary referrals was reduced from 22% to 8.2%, while that of missed patients decreased slightly (from 21% to 16%), with the number of patients diagnosed per RF request remaining unchanged. In terms of costs, we saved 19.4 RF tests per anti-CCP test added.We developed a simple and cost-effective strategy for reducing the time to diagnosis of RA that can improve patients' quality of life. This approach was supported by primary and specialised care.