Multicenter evaluation study on a new HEp2 ANA screening enzyme immune assay

The COBAS(R) Core HEp2 ANA enzyme immune assay (EIA) was evaluated in a pre cision and a clinical sample study in comparison to indirect immunofluoresc ence assay (IFA) on HEp2-cells. In the precision study the COBAS(R) Core EI A yielded intraassay coefficient variations (CVs) mostly below 9%, and inte rassay CVs between 4.7% and 10.4%. When comparing the COBAS(R) Core EIA to IFA, the results corresponded well in healthy subjects, systemic lupus eryt hematosus, mixed connective tissue disease and rheumatoid arthritis. In the case of Sjogren's syndrome and scleroderma patients the COBAS(R) Core EIA yielded a lower rate of positive results compared to IFA. This discrepancy may be explained by the lack of detection of autoantibodies to nuclear anti gens that can be identified only by IFA due to their compartimentalization and higher localized antigen density in HEp2 cells. The discrepancies in th e group of dermato/polymyositis patients are due to the fact that the EIA c ontains mainly nuclear antigens and was able to detect only antibodies agai nst the cytoplasmic Jo1 antigen that was added to the HEp2 nuclear extract. Routine sera were also evaluated; good agreement was found in sera from pa tients attending tertiary reference centres for autoimmune diseases but a h igher number of discrepancies was reported in sera from unselected populati ons. (C) 1999 Academic Press.