A fluorescence sedimentation assay for dsDNA antibodies

Area of Science:

• Immunology
• Biochemistry
• Clinical Diagnostics

Background:

• The traditional Farr assay, a radioimmunoassay (RIA), detects dsDNA antibodies for systemic lupus erythematosus (SLE) diagnosis.
• RIA-Farr assay offers high sensitivity and specificity but involves radioactive materials and requires technical expertise.
• Disadvantages of radioactivity and handling safety necessitate alternative diagnostic methods.

Purpose of the Study:

• To develop and validate a novel, non-radioactive precipitation assay, the Fluoro-Farr assay, for detecting dsDNA antibodies.
• To evaluate the diagnostic efficiency of the Fluoro-Farr assay for SLE.
• To compare the performance of the Fluoro-Farr assay with the established RIA-Farr assay.

Main Methods:

• The Fluoro-Farr assay utilizes polyethylene glycol (PEG) precipitation and EvaGreen fluorescence for dsDNA antibody detection.
• Assay validation involved testing 57 sera from SLE patients and 60 healthy controls.
• Diagnostic performance was assessed using receiver operating characteristic (ROC) curve analysis.

Main Results:

• The Fluoro-Farr assay demonstrated a diagnostic sensitivity of 68% and a specificity of 95% (ROC AUC 0.91).
• A good correlation was observed between the Fluoro-Farr assay and the RIA-Farr assay results.
• The RIA-Farr assay maintained superior diagnostic efficiency (ROC AUC 0.99) compared to the Fluoro-Farr assay.

Conclusions:

• The Fluoro-Farr assay is a viable, non-radioactive alternative to the RIA-Farr assay, particularly for labs lacking radioactivity handling facilities.
• Both assays function as precipitation assays, enabling antibody:dsDNA interaction in solution with native dsDNA.
• While Fluoro-Farr eliminates radioactivity risks, RIA-Farr remains the gold standard for diagnostic performance in SLE detection.