Outcomes in Seronegative Rheumatoid Arthritis and Undifferentiated Arthritis

Seronegative rheumatoid arthritis (SNRA) and undifferentiated arthritis (UA) are heterogeneous conditions that are often reclassified to more specific diagnoses. We report a retrospective chart review from the United States military health system (MHS) that examines clinical characteristics, reclassification rates, and potential predictors of reclassification in SNRA and UA.

The study included MHS beneficiaries diagnosed with SNRA or UA. Inclusion criteria consisted of a negative rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibody at presentation, synovitis on a rheumatologist's exam, and treatment with a disease-modifying anti-rheumatic drug (DMARD). We then recorded clinical characteristics including distributions of joint involvement, erosions or extra-articular disease, and the number of clinic visits. We used binomial logistic regression to evaluate for any predictors of future diagnostic reclassification.

One hundred thirty-three patients were included, with an index diagnosis of SNRA in 20 (15%) patients, and UA in 113 (85%) patients. Eighty-five (63.9%) patients were later reclassified to other diagnoses, including SNRA (52.1%), seropositive rheumatoid arthritis (9.4%), psoriatic arthritis (14.6%), spondyloarthritis (14.6%), and other (9.4%). The regression model was statistically significant (X2(7) = 15.747, P = .028) and explained 15% of the variance in diagnostic reclassification. Although most variables failed to reach significance, more clinic visits predicted greater odds of diagnostic reclassification (OR 1.07, CI 1.03-1.12).

Our data indicate a potential association with the frequency of follow-up with the likelihood of future diagnostic reclassification in SNRA and UA, suggesting that diagnostic accuracy may be higher in patients with more frequent follow-up visits.