Objective To investigate the expression of serum tumor-associated antigens (TAAs) in patients with rheumatoid arthritis (RA) and analyze their clinical significance for RA.

Methods A total of 214 RA patients were enrolled in the RA group, while 198 age- and gender-matched healthy individuals were included in the HC group. Rheumatoid factor (RF), anti-cyclic citrullinated peptide antibody (Anti-CCP), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), interleukin-6 (IL-6), ferritin levels, as well as gender, age, disease duration, disease activity score (DAS28) and clinical manifestations were collected from the RA group. The expression of TAAs in RA patients and the clinical characteristics of TAA-positive patients were analyzed. Spearman correlation analysis was used to evaluate the relationships between TAAs and clinical indicators in RA patients.

Results The positive rate of carbohydrate antigen 125 (CA125) in the RA group was 8.88%, which was significantly higher than 1.01% in the HC group (P < 0.001). Serum CA125 and cytokeratin fragment 19 (CYFRA21-1) levels in the RA group were significantly higher than those in the HC group, whereas alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), carbohydrate antigen 199 (CA199) and neuron-specific enolase (NSE) levels were significantly lower (P < 0.001). TAA-positive patients had significantly older age and higher rates of pulmonary interstitial lesions compared to TAA-negative patients (P < 0.05). Patients with DAS28 scores >5.1 had significantly higher CA125 levels than those with DAS28 scores ≤5.1 (P < 0.05). CA125 levelswere positively correlated with DAS28 scores, ESR, RF, and anti-CCP antibodies (r=0.142, 0.140, 0.268, 0.183; P < 0.05).

Conclusion In RA patients, the positivity rate and levels of some serum TAAs are elevated, and TAA-positive patients tend to be older and have higher incidence of pulmonary interstitial lesions. CA125 levels are positively correlated with RA disease activity.