Background Determination of antinuclear antibodies (ANA) is very important for diagnosis and prognosis of several systemic autoimmune rheumatic diseases (SARD). Indirect immunofluorescence (IIF) method on HEp-2 cells is gold standard for routine ANA detection although some investigators strongly advocate that specific test for anti-Ro/SSA antibodies should be always included, bearing in mind that expression of Ro/SSA antigen on HEp-2 cells is variable.
Objectives The aim of this study was to examine the frequency and possible clinical significance of positive anti-Ro/SSA antibodies in IIF-ANA negative samples.
Methods Five hundred consecutively remitted serum samples from different patients for both ANA and anti-Ro/SSA testing were analysed and patients records were checked in order to achieve information concerning the clinical diagnosis. Anti-Ro/SSA antibodies were detected by ELISA test (Orgentec, Germany) and ANA by IIF method on HEp-2 cells (Biosystems, Spain).
Results The most common diagnoses of patients referred to the laboratory testing were arthralgia/arthritis and unspecified connective tissue diseases in 187 (37.4%) and 185 (37%) cases respectively, followed by Syndroma Sjogren in 79 (15.8%), inflammatory eye disorders in 22 (4.4%), SLE in 16 (3.2%), vasculitis in 9 (1.8%) and malignancies in 2 (0.4%) cases. Antinuclear antibodies were detected in 259 sera. The IF staining patterns in these sere were homogeneous in 119 cases, speckled in 84, nucleolar in 5, centromeric in 7, PCNA and peripheral in 1case. Mixed staining pattern was observed in 42 cases. Anti-Ro/SSA antibodies were detected in 57 (22%) IIF-ANA positive sera predominantly with speckled and homogeneous IF staining pattern. Concentration of anti-Ro/SSA antibodies significantly correlated with ANA titre (p<0.001). In 10 (4.15%) out of 241 IIF-ANA negative sera anti-Ro/SSA antibodies were detected. Diagnosis of Syndrome Sjogren was confirmed in 4 cases, three patients had arthritis, two patients undifferentiated connective tissue disease and one malignancy.
Conclusions Our results confirmed that using IIF method for ANA testing anti-Ro/SSA positivity can be missed but in low percent of samples. In case of high index of suspicion of SARD addition of specific test for anti-Ro/SSA antibodies to IIF-ANA testing is meaningful. We do not recommend both testing to rule out diagnosis of SARD.
Dahle C, Skogh T, Aberg AK, Jalal A, Olcén P. Methods of choice for diagnostic antinuclear antibody (ANA) screening: benefit of adding antigen-specific assays to immunofluorescence microscopy. J Autoimmun. 2004 May;22(3):241-8.
Mahler M, Meroni PL, Bossuyt X, Fritzler MJ. Current concepts and future directions for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies. J Immunol Res. 2014; doi: 10.1155/2014/315179.
Disclosure of Interest None declared