099 - Evaluation of 4 diagnostic kits for the search of anti-nuclear antibodies by indirect immunofluorescence on HEp-2 and HEp-2000
Autor(s): Tonutti E, Picierno A, Visentini D, Butazzoni M, Molinaro P, Grimaldi E, Bizzaro N
Issue: RIMeL - IJLaM, Vol. 3, N. 2, 2007 (MAF Servizi srl ed.)
Page(s): 99-105
Background. The diagnosis of connective tissue disease (CTD) is based on clinical and immunological criteria. Among them, the anti-nuclear antibodies (ANA) hold a determining role and represent the first laboratory approach in the diagnosis of CTD. The objective of this study was to evaluate the analytical characteristics and diagnostic sensitivities of four commercial methods for the detection for ANA by indirect immunofluorescence Methods. Four different IIF tests (Inova, Euroimmun, BioRad, ImmunoConcepts) were used to search for ANA in 409 sera (328 of them came to the lab with a request for ANA search, 81 were selected because either ANA and/or ENA positive). The 4 ANA kits were evaluated based on the various analytical methods, the substrate characteristics, the fluorescence pattern and title, and the anti-ENA and anti-dsDNA positivities. The clinical sensitivity of each kit was calculated on 78 CTD diagnosed sera. Results. The percentage of the ANA positivities (≥1:40) was: 59% with Euroimmun and Bio-Rad, 58% with ImmunoConcepts and 52% with Inova. 86 sera were positive for anti-ENA antibodies (39 anti-SSA, 6 anti- SSB, 23 anti-SSA/SSB, 8 anti-RNP, 6 anti-Scl70, and one each anti-Sm, anti-RNP/Sm, SSA/Jo1 and Jo1). 14 were positive for anti-dsDNA with comparable results among the 4 kits. The biggest difference was noted in the anti-SSA antibody. Of the 39 sera showing isolated anti-SSA positivity, 8 (20%) were ANA negative with the Inova kit, 9 (23%) with the Euroimmun kit, 10 (26%) with Bio-Rad, and 5 (13%) with ImmunoConcepts. Similarily, in the 78 sera of patients affected by CTD, the large majority of the negative results were observed in anti-SSA positive patients with Sjögren’s syndrome. The Inova kit was negative in 9% of the cases, Euroimmun and Bio-Rad in 10%, and ImmunoConcepts in 2.5%. Conclusions. The performance of the four ANA kits was more than satisfactory. Considering the inherent difficulties of the IIF method, the comparison has shown acceptable levels of diagnostic and analytic sensitivity for all the methods evaluated. The ImmunoConcept kit provided higher sensitivity percentages in the group of patients with anti-SSA antibodies. Key words: Anti-nuclear antibodies, indirect immunofluorescence, HEp-2, HEp-2000, diagnostic accuracy.