Analysis of Rheumatoid Arthritis Autoantibodies Helps in Classification

The concordant presence of rheumatoid arthritis (RA) autoantibodies independently contributes to the classification of patients with early arthritis, according to study results published in Arthritis Research & Therapy. The included autoantibodies were rheumatoid factor, anti-citrullinated protein, and anti-carbamylated protein antibodies.

The study included data from the first visit of 1057 patients in 2 early arthritis prospective cohorts. At 2 years of follow-up, the researchers assessed the serologic scores from the 2010 ACR/EULAR classification criteria and the concordant presence of the 3 RA autoantibodies relative to a gold standard comprised of the RA classification with the 1987 ACR criteria.

The results indicated that the concordant presence of 3 antibodies demonstrated predictive characteristics that allowed for direct classification as RA (positive predictive value [PPV], 96.1% and odds ratio [OR], 80.9). Compared with the high antibody titers defined in the 2010 classification criteria (PPV, 88.8%; OR, 26.1), the antibodies performed significantly better.

In addition, the researchers found that the concordant presence of 2 antibodies also demonstrated predictive characteristics (PPV, 82.3%; OR, 15.1).

With these results, the researchers devised a scoring system based only on antibody concordance that had similar overall performance compared with the serologic scoring system of the 2010 criteria. However, the best-performing classification combined the concordance with the 2010 serologic systems.

The researchers did not note any study limitations. However, they did acknowledge the possibility that other autoantibodies could improve RA classification.

“The full advantage of the predictive power of anti-body concordance will require modification of the weights given to each stratum of RA patients in the whole classification criteria,” the researchers wrote.

Reference

Regueiro C, Rodríguez-Martinez L, Nuño L, et al. Improved RA classification among early arthritis patients with the concordant presence of three RA autoantibodies: analysis in two early arthritis clinics [published online December 11, 2019]. Arthritis Res Ther. doi:10.1186/s13075-019-2079-4