Background/Purpose

Twenty-nine sera from 348 primary Sjögren’s syndrome patients were identified as anti-Ro60 (anti-SSA) negative and anti-La (anti-SSB) positive by immunodiffusion, line immunoassays and multiplex bead assays. We hypothesize that a significant portion of these are falsely negative for anti-Ro60.  

Methods

Twenty-nine sera from primary Sjögren’s syndrome patients, fulfilling four AECG criteria, were tested for the presence of antibodies directed against La and Ro60 autoantigen. Anti-La was detected on bovine La treated with or without DNAase and RNAase (to check for false positivity, since anti-La can bind DNA and RNA). Anti-Ro60 antibodies in the sera were detected using HEp-2000 substrate (in which cells are transfected with human Ro60) and HEp-2 substrate. Anti-Ro60 and Ro-52  were also tested by in vitrotranscription/translation/immunoprecipitation assay.  

Results

Out of the 29 sera, 25 were unequivocally negative on HEp-2000 (1:40 dilution). Four samples were clearly found to be Ro60 positive with a speckled pattern and three of the four continued to be positive up to 1:320 dilution, as against only two positive samples on HEp-2 at 1:40 dilution. This finding suggests false negativity for Ro60 exists in a small fraction (14 percent) of primary Sjogren’s syndrome patients. However, all the samples were negative for Ro60 and Ro52 by in vitrotranscription/translation/immunoprecipitation assay. 

Conclusion

Contrary to our hypothesis, we found only a small fraction of Ro negative, La positive sera to show positive HEp-2000 pattern. This suggests that a subset of primary Sjogren’s syndrome is probably a true entity with Ro60 negativity and La positivity. The clinical significance of the subset will be revealed during the follow up of our patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/la-positive-ro60-negative-subset-of-primary-sjogrens-syndrome-is-a-reality/