Clinical research on progress of antinuclear antibody in rheumatoid arthritis

Rheumatoid arthritis (RA) is a common chronic, systemic autoimmune disease characterized by erosive arthritis, with a global prevalence of 0.25% to 1.00%, which may ultimately lead to joint deformity and loss of function. Antinuclear antibody (ANA) refers to auto-antibodies that target various components of eukaryotic cells. Although ANA may be frequently detected in RA patients, with a positive rate of 30% to 60%, the significance of ANA in the diagnosis and treatment of RA remains unclear. Nuclear patterns in RA population are dominated by speckled and homogeneous patterns, mainly at low titres. The detection rate of extractable nuclear antibodies is usually lower than that of ANA. The serum levels of rheumatoid factor and anti-cyclic citrullinated peptide antibody in ANA-positive RA patients are much higher than ANA-negative ones, and joint erosion of ANA-positive RA patients had more severe joint erosion on imaging as well. Therefore, ANA is a potential predictor of severe joint injury. ANA-positive RA patients are more likely to have extra-articular manifestations [such as subcutaneous nodules(82% vs 46%), ocular lesions(38% vs 6%), and infections(38% vs 12%)].In terms of RA comorbidities, compared to the ANA negative group, the ANA positive group had higher levels of moderate and severe anemia (16.04% vs 6.9%; 6.6% vs 0.07%), Sjogren's syndrome (19.5% vs 4.1%), and vasculitis (29% vs 7%). In addition, ANA positivity is an independent risk factor for elderly RA patients with carotid intimal thickening (HR=4.089) and adverse pregnancy outcomes in female RA (OR=3.268, P=0.045), respectively. Attention should be paid to high-titre ANA-positive RA patients for preventive measures. In terms of treatment, RA patients who are ANA-positive when given tumour necrosis factor-α inhibitor (TNFi) treatment got much poorer therapeutic response than ANA-negative ones, especially those with high titres were more prone to generating anti-drug antibodies. Increase of ANA titer induced by TNFi is associated with no response to TNFi treatment, thus monitoring the change of ANA may predict the long-term efficacy of TNFi. The most common adverse event of TNFi is drug-induced lupus. Although it has been confirmed that the induction of anti-double-stranded DNA antibodies is associated with poor efficacy of TNFi, large-scale studies are still needed to confirm the correlation between the increase of ANA titer or ocurence of dsDNA antibody and the induction of drug-induced lupus. In conclusion, this paper reviews the research progress on ANA characteristics in RA population, clinical manifestations of ANA-positive RA, and the association between ANA and TNFi prognosis. The potential of ANA as a new biomarker of RA needs to be further studied.