A comparative study of immunological methods for determination of serum antinuclear antibodies.

INTRODUCTION Several immunological methods are used to determine the serum antinuclear antibodies (ANA). Indirect immunofluorescence assay (IFA) with tissue slices or HEp-2 cells is the standard technique considered the gold standard for their screening. Serum-free McCoy-Plovdiv cell line may also be used as substrate for IFA. Another method for detection of total and specific ANA is the enzyme-linked immunosorbent assay (ELISA). Immunoblot is also applied in specific ANA confirmation. The aim of the current study was to determine and propose a justified immunological approach for identification of clinically significant ANA by comparing the screening tests - ANA-IFA on serum-free McCoy-Plovdiv cell substrate with ELISA for total ANA, and confirmative methods for specific ANA-ELISA with immunoblot. MATERIALS AND METHODS Serum samples from 38 patients screened for totalANA by ELISA (Trinity Biotech, NY, USA) and IFA-ANA with McCoy-Plovdiv cell line, were included in the study. Positive samples were confirmed by immunoblot (Orgentec Diagnostika, Germany) and ELISA for specificity of confirmed ANA. RESULTS No significant difference (P > 0.05) and very good agreement were found between the two screening tests. Very good agreement for specific antibodies against SS-A, SS-B, dsDNA, moderate for anti-Sm and anti-Sm/RNP and fair for anti-histone/nucleosomal antibodies was found between confirmative methods. No agreement was found for anti-Scl-70 antibodies. CONCLUSION IFA-ANA with serum-free McCoy-Plovdiv cell line and screening ELISA may be recommended for determination of total ANA, and immunoblot and ELISA- for confirmation and identification of specific ANA.