Sensitivity of the Phadia EliA connective tissue disease screen for less common disease-specific autoantibodies.

AIM: To evaluate the sensitivity of a commercial autoantibody screening method (Phadia EliA connective tissue disease (CTD) screen) for the detection of less common antibody specificities associated with connective tissue disease. METHODS: 399 sera positive for anti-PM/Scl (n=102), anti-RNA polymerase III (n=199), anti-fibrillarin (n=50), anti-Mi-2 (n=12), anti-proliferating cell nuclear antigen (PCNA) (n=13) and anti-ribosomal P (n=23) were analysed using the solid phase assay. Each well was coated with the respective antigens for these autoantibodies and also with the antigens Ro, La, Jo-1, Scl-70, CENP-B, U1-RNP, Sm and native DNA. RESULTS: All the anti-ribosomal P, anti-PCNA and anti-Mi-2 sera and 94% of the anti-PM/Scl sera were positive. For anti-fibrillarin, 36 (68%) were positive and 12 (22%) were equivocal. For anti-RNA polymerase III, 131 (67%) were positive, 23 (11%) were equivocal and 45 (22%) were negative. CONCLUSIONS: The sensitivity of the Phadia EliA CTD screen is currently insufficient for the assay to be used as a screening test for anti-fibrillarin and anti-RNA polymerase III, but appears to be satisfactory for the other autoantibodies tested.

A longitudinal study of anti-RNA polymerase III antibody levels in systemic sclerosis.

OBJECTIVES: Anti-RNA-polymerase antibodies (ARAs) are associated with the diffuse cutaneous subset of SSc (dcSSc) and particularly with scleroderma renal crisis (SRC). We analysed serial ARA levels and explored the relationship with clinical features and disease outcome. METHODS: A commercially available ELISA method with a recombinant peptide of RNA polymerase III was used and ARA levels were measured in a well-characterized cohort of SSc cases. RESULTS: ARA levels were measured in 64 SSc patients. Of them, 78% (n = 50) were females and 92% (n = 59) had dcSSc, 39% (n = 25) had SRC, 20% (n = 13) had pulmonary fibrosis (PF), 9% (n = 6) had pulmonary arterial hypertension and 3% (n = 2) had cardiac involvement. There was considerable inter- and intra-patient variability in ARA levels (11-210 U/ml). There was no correlation between absolute ARA levels (at baseline or throughout the disease course) and outcome. There was a moderate correlation between time to peak ARA level and development of significant PF (Pearson correlation = 0.669, P = 0.034), but no correlation between peak ARA levels and onset of SRC. ARA levels change correlated with change in skin score (correlation coefficient within subjects = 0.236, P = 0.011). CONCLUSIONS: The pathogenic significance of ARA is unclear. Despite the very strong association of ARA with SRC, we could not show the clinically significant association between absolute levels of antibody and development of internal organ complications, which makes repeated measurements of ARA levels unnecessary. However, changes in ARA level over time occur and may reflect changes in skin score.

Prevalence of antibodies to Ro-52 in a serologically defined population of patients with systemic sclerosis.

BACKGROUND: Antibodies against Ro-52 have been described in patients with a broad spectrum of autoimmune disease, most commonly in association with anti-Ro-60 in systemic lupus erythematosus and Sjogrens syndrome. However, in inflammatory myositis anti-Ro-52 is frequently present without anti-Ro-60 and is closely linked to the presence of aminoacyl-tRNA synthetase (aats) antibodies. To date there have been no comprehensive reports on the frequency of anti-Ro-52 in systemic sclerosis (SSc), a disease characterised by hallmark autoantibodies that occur in non-overlapping subsets. Clinically, each antibody-defined group has a distinct pattern of organ involvement, some featuring myositis. OBJECTIVES: To determine the frequency of anti-Ro-52 in serologically defined groups of SSc patients and to investigate a possible link with myositis-associated autoantibodies. METHODS: Serum samples from 1010 patients with SSc and 55 and 32 patients with anti-aats and anti-Ku respectively were tested for the presence of anti-Ro-52 using a commercial ELISA. RESULTS: The prevalence of anti-Ro-52 was 15-38% in nine of the eleven sub-groups. There were no significant differences in mean anti-Ro-52 levels in these groups with the exception of that defined by the presence of anti-U1-RNP. In the remaining groups defined by anti-Ro-60 and anti-aats, anti-Ro-52 was present in 92% and 100% respectively. In sera from non-SSc patients with anti-aats, anti-Ro-52 was detected in 64%. CONCLUSION: Anti-Ro-52 is present throughout the SSc population. It is neither more prevalent in the myositis-associated antibody groups nor does it segregate with any other major SSc-specific autoantibodies. The co-existence of anti-Ro-52 with both anti-Ro-60 and anti-aats is confirmed.