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

Area of Science:

• Immunology
• Clinical Chemistry
• Autoimmune Diseases

Background:

• Antinuclear antibodies (ANA) are key biomarkers for autoimmune diseases.
• Indirect immunofluorescence assay (IFA) is a standard method for ANA detection.
• Enzyme immune assays (EIAs) offer potential for standardized ANA testing.

Purpose of the Study:

• To evaluate the performance of the COBAS Core HEp2 ANA enzyme immune assay (EIA).
• To compare the COBAS Core EIA with the indirect immunofluorescence assay (IFA) for ANA detection.
• To assess the clinical utility of the COBAS Core EIA in various autoimmune conditions.

Main Methods:

• Precision study evaluating intra-assay and inter-assay coefficients of variation (CVs) for the COBAS Core EIA.
• Clinical sample study comparing COBAS Core EIA results against HEp2-cell IFA.
• Evaluation of sera from patients with systemic lupus erythematosus, Sjögren's syndrome, scleroderma, and dermato/polymyositis.

Main Results:

• COBAS Core EIA demonstrated good precision with intra-assay CVs mostly below 9% and inter-assay CVs between 4.7% and 10.4%.
• Good agreement between COBAS Core EIA and IFA was observed in healthy subjects and patients with systemic lupus erythematosus, mixed connective tissue disease, and rheumatoid arthritis.
• Lower positive rates were observed with COBAS Core EIA in Sjögren's syndrome and scleroderma patients compared to IFA, potentially due to differences in detectable autoantibodies.
• Discrepancies in dermato/polymyositis were linked to the EIA's focus on nuclear antigens and limited detection of cytoplasmic antibodies like Jo1.

Conclusions:

• The COBAS Core HEp2 ANA EIA exhibits acceptable precision and good agreement with IFA for certain autoimmune diseases.
• The EIA may underdetect specific autoantibodies identifiable by IFA, particularly in conditions like Sjögren's syndrome and scleroderma.
• Clinical performance varied between reference centers and unselected populations, highlighting the need for careful interpretation in diverse patient groups.