Comparative analysis of Anti-RA33 antibodies and Rheumatoid Factor (RF) in diagnosing Rheumatoid Arthritis among seropositive and seronegative patients in Coimbatore districts of Tamil Nadu

Abstract

Rheumatoid factor (RF), an immunological marker is the very first sero-marker used in the diagnosis of RA. An alternative to this scenario was seemed to have been aided by another marker, RA33 in identification of RA patients, who come under the category of sero-negativity RF tests. The main aim is to compare Rheumatoid Factor (RF) and Anti- RA33, to ensure which marker is more effective in diagnosing the rheumatoid arthritis patients. The cross sectional study was conducted for about three years from January 2020 – February 2023. A total of one hundred and fifty serum samples were collected from patients which includes 72 seropositive for RA and remaining 84 from seronegative RA patients.Among the 72 RA positive patients, 20 positive for anti-RA33 antibodies and the remaining 52 were negative. In case of 84 RA negative patients, 17 were positive and remaining 67 negative for the same. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 55.29%, 54.65%, 28.14% and 81.2% respectively. Anti RA33 has proved to be an amazing biomarker for seropositive as well as seronegative patients. In the case of seronegative patients, where RF is negative or undetectable, Anti RA33 serves as an indeed essential marker. The study concludes that anti-RA33 antibodies could be a good marker but statistically couldn’t be able to make a decision that it is a better marker than the RF.