HEp2 ANA EIA: a new fully automated assay for the screening of antinuclear antibodies.

BACKGROUND: Screening for antinuclear antibodies is performed for various systemic autoimmune diseases with various different techniques. A more recent approach to ANA screening is the use of enzyme immunoassays. OBJECTIVES: To introduce the new COBAS CORE HEp2 ANA EIA, the first fully automated enzyme immunoassay for the detection of ANA in serum and plasma of patients with suspected systemic autoimmune disease. METHODS: A method comparison between the new HEp2 ANA EIA and immunofluorescence assays on HEp2 cells was performed in two groups--977 patients with systemic autoimmune disorders and 952 healthy subjects with no autoimmune disease-related diagnosis. RESULTS: The clinical sensitivity in the patient group was 79.8% for HEp2 ANA EIA and 89.5% for IFA, and the clinical specificity in the control group was 91.7% for HEp2 ANA EIA and 93.9% for IFA. The analysis of 830 routine samples showed an overall good concordance of 85% between both assays. Further examination of the discrepant results showed 8% discrepant negative results for the HEp2 ANA EIA assay compared to 21% for IFA. Discrepant positive results were found in 37.9% and 33% of samples for the HEp2 ANA EIA and the IFA, respectively. CONCLUSION: The HEp2 ANA EIA is the first fully automated assay for the detection of ANA in serum and plasma. The assay shows improved sensitivity in ANA determination and a similar performance, compared to the standard method of IFA.