Background Accurate and early diagnosis of rheumatoid arthritis (RA) is vital for the timely implementation of a comprehensive treatment aimed at halting or slowing its progression (1). The sensitivity of existing biomarkers, rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibodies (anti-CCP) is low (2). It requires a new diagnostic biomarker with better performance in RA.
Objectives To evaluate the diagnostic value of anti-RA33 (3) test in a simple of RA patientes and controls of Bogotá, Colombia, by measuring its sensitivity, specificity, positive and negative likehood ratio compared to RF and anti-CCP. Additionally, to asses the association between clinical and serological variables with the functional impairment degree in patients with RA.
Methods A cross-sectional study in a sample of 80 RA patients and 20 controls without RA who attended to outpatient service in two hospitals of Bogotá from 2014 until 2015 was conducted by measuring their sociodemographic characteristics, arthritis activity degree by DAS-28 index, functional ability by HAQ-DI score and serological status for anti-RA33, RF and anti-CCP. A statistic analysis with proportions, summary and dispersion measures, contingency tables for measure of sensitivity, specificity, likehood ratios, ROC curves and multiple linear regression analysis was performed.
Results Sensitivity score for anti-RA33, RF and anti-CCP was 15%, 85% and 93% respectively; while specificity was 100%, 90% and 85% respectively. The positive likelihood ratio was 8.5 for RF and 6.2 for anti-CCP. Finally, negative likelihood ratio was 0.87 for anti-RA33, 0.16 for RF and 0.08 for anti-CCP. The anti-RA33 seropositive patients were greater arthritis activity and functional disability as well as higher titers of RF and anti-CCP although these differences were not statistically significant. Finally, a moderately strong positive correlation was found between DAS-28 and HAQ-DI scores (R2 =0.51). In the multiple linear regression model, DAS-28 index was the only predictor variable that explained the changes in the HAQ-DI functional ability score.
Conclusions Findings suggest that anti-RA33 test does not seem to have any clinical utility for the diagnosis of RA in Colombian population. The importance of DAS-28 activity index as a score of association with functional disability in patients with RA was confirmed.
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Disclosure of Interest None declared