Screening for antinuclear antibodies by enzyme immunoassay

Area of Science:

• Clinical immunology
• Autoantibody detection
• Diagnostic assay development

Background:

• Indirect fluorescent antibody (IFA) is the standard for antinuclear antibody (ANA) screening.
• Subjectivity in IFA interpretation and high ANA-negative rates necessitate improved screening methods.
• Enzyme immunoassay (EIA) screens offer a potential objective and efficient alternative.

Purpose of the Study:

• To compare the performance of five commercial ANA EIA screens against the established IFA method.
• To evaluate the sensitivity and specificity of EIA assays for ANA screening in a clinical laboratory setting.
• To assess the utility of EIA as a high-throughput screening tool for autoantibodies.

Main Methods:

• Five ANA EIA kits (Elias, Helix, Sanofi, TheraTest, Zeus) were evaluated against IFA using HEp-2 cells.
• Sera from 601 patients and 202 healthy donors were tested.
• Discordant results were further analyzed using single-antigen EIAs; IFA titers ≥1:160 were considered positive.

Main Results:

• Agreement, sensitivity, and specificity varied among EIA kits compared to IFA.
• TheraTest (95.3% agreement, 97.7% sensitivity, 93.5% specificity) and Sanofi (95.0% agreement, 93.7% sensitivity, 95.9% specificity) showed high performance.
• EIA methods demonstrated objectivity and reduced labor compared to IFA for large sample volumes.

Conclusions:

• Commercial ANA EIA screens are sensitive and specific alternatives to IFA, particularly for high-volume laboratories.
• EIA offers objective, less labor-intensive screening, effectively identifying ANA-negative samples.
• Confirmation of positive EIA screens by IFA is recommended to determine titers and patterns.