A Homogeneous Immunoassay Method for Detecting Interferon-Gamma in Patients with Latent Tuberculosis Infection

Area of Science:

• Immunology
• Infectious Diseases
• Biotechnology

Background:

• Interferon-gamma release assays (IGRAs) are crucial for diagnosing latent tuberculosis infection (LTBI).
• Existing IGRA methods require optimization for speed and accuracy in LTBI detection.
• Quantifying interferon-gamma (IFN-γ) is key to effective LTBI diagnostics.

Purpose of the Study:

• To develop and validate a novel luminescent oxygen channeling immunoassay (LOCI) for quantifying IFN-γ in IGRAs.
• To assess the performance characteristics of the LOCI IFN-γ assay for diagnosing LTBI.
• To compare the efficacy of the LOCI IFN-γ assay against the established T-SPOT.TB test.

Main Methods:

• A customized homogeneous sandwich luminescent oxygen channeling immunoassay (LOCI) was developed.
• IFN-γ levels were measured in samples from healthy volunteers and T-Spot-positive patients.
• The LOCI IFN-γ assay was evaluated for sensitivity, specificity, accuracy, reproducibility, and assay time.

Main Results:

• The LOCI IFN-γ assay demonstrated low background, high sensitivity, specificity, accuracy, and reproducibility.
• The assay achieved a short turnaround time of 30 minutes with excellent recovery (81.63-102.06%) and low coefficients of variation (<5%).
• Excellent agreement (97.2% agreement, κ = 0.94) was observed between LOCI IFN-γ and the T-SPOT.TB test, with significantly higher IFN-γ levels in T-Spot-positive patients.

Conclusions:

• The LOCI IFN-γ assay is a validated in vitro blood test for LTBI diagnosis.
• The assay exhibits acceptable performance characteristics, including high agreement with T-SPOT.TB, confirming its utility for LTBI detection.
• This novel assay offers a rapid and reliable method for diagnosing LTBI.