Padrões de imunofluorescência do fator antinuclear (FAN) em células HEp-2 de soros reagentes para anti-SSA/Ro

Abstract

OBJECTIVE: to evaluate the pattern at immunofluorescence of the antinuclear antibodies (ANA) detected by the indirect immunofluorescence (IIF) technique in positive samples for anti-SSA/Ro autoantibody and the clinical associations. METHODS: a retrospective transversal study was performed in a period of two years where the all the solicitations of testing for the presence of anti-extractable nuclear antigen (anti-ENA) antibodies delivered to the SPC/HCPA were analyzed. We selected the positive samples and identified which autoantibodies were involved (anti-SSA/RO, anti-SSB/La, anti-RNP, anti-Sm and anti-Scl70) as well as the immunofluorescence patterns by ANA testing and the clinical associations found in the patients presenting anti-SSA/Ro positive serum. IIF was used for ANA using HEp-2 cells and hemagglutination for anti-ENA antibodies detection. RESULTS: 90 out of the 392 solicitations analyzed were anti-ENA positive, with a predominance of women (86/91 - 94%) and the mean age was 42 years old. The most frequent autoantibody was anti-SSA/Ro (61/90 - 67.8%) and all samples that were anti-SSA/Ro positive were also ANA positive. Speckled nuclear immunofluorescence was the most frequent ANA pattern (42/61 - 68.9%) among the anti-SSA/Ro positive samples and systemic lupus erythematosus was the most common clinical diagnosis (31/61 - 50.8%). CONCLUSION: ANA testing by IIF using HEp-2 cells proved to be a good screening test for the detection of anti-SSA/Ro antibodies, that showed a strong positive association to the speckled nuclear IIF pattern. As opposed to what has been described in the literature, there was no ANA negative among the anti-SSA/Ro positive samples. At least in our experience, these data question the cost-effectiveness of performing routine screening for anti-SSA/Ro antibodies in ANA negative samples by IIF testing.