Background and Aims

The development of new automated ANA screening techniques, based in simultaneous detection of autoantibodies using an array of purified/recombinant antigens has allowed identify patients who are isolated positive for some autoantibodies and who nevertheless do not have the clinic associated with these antibodies . The anti-RNP-A antibodies have very low specificity and are very often founded in the general asymptomatic population.

GOAL: To determine if these anti-RNP-A“false positives” could be identifying people who later developed an immune-mediated inflammatory disease (IMID).

Methods

310 patients isolate positive for anti RNP-A (BioPlex® 2200) and negative for ANA-immunofluorescence in the period 2012-2015 were followed-up prospectively until October 2019 (3-7 years)

Results

78 patients (25%) had previous IMID diagnosis (38.5% RA, 11.5% IBD-associated spondyloarthritis, 9% SLE, 7.7% APs, 6.4% PMR, 5% Sjögren's syndrome, 3.8% EspA-ax, and 18.1% others.
Of the 232 patients without IMID, in 76 (33%) ANA was request by routine and no follow-up was performed. In the other 156 (67%) during the follow-up, a diagnosis of IMID was reached in 23 patients (14.7%). Only in 9 (5.8%) was diagnosed an ANA-associated connective disease (1 SLE, 1 SLE induced by anti-TNFα, 2 EMTC, 2 SAF, 3 Sjögren), The other 14 (8.9%) had other autoimmune diseases not ANA-associated (5 APs, 3 RA, 2 PMR, 1 EspA-ax, 3 vasculitis). The others 133 patients (85.3%) continued without IMID

Conclusions

Our series shows only a small percentage of patients with isolated anti-RNP + get to develop an immune-mediated disease over several years of follow-up.