The sensitivity, specificity, likelihood ratio, positive predictive value (PPV), negative predictive value (NPV), and accuracy of RA diagnosis according to the presence of citrullinated filaggrin were 78.9%, 85.9%, 5.6, 92%, 66.3%, and 80.8%, respectively, when using an OD cut-off value of 1.013. This evidence concerns the gene FLG and rheumatoid arthritis.