Overview: Interferon-Gamma Release TestIntroduction: The Interferon-Gamma Release Test measures interferon-gamma release to diagnose infections like tuberculosis, helping guide treatment for chronic cough or fever. Affecting 1 in 3,000 people with latent TB, this test poses diagnostic challenges due to asymptomatic cases. Following 2023 Centers for Disease Control and Prevention (CDC) guidelines, it uses ELISA for high sensitivity, supporting immunology screening. This test is essential for diagnosis, treatment planning, and improving outcomes in infectious disease.
Other Names: IGRA Test, TB Infection Assay.
FDA Status: FDA-approved test, meeting immunology standards for diagnostic reliability.
Historical Milestone: Interferon-gamma testing began in the 1990s with research by Andersen, who developed the assay. ELISA advancements in the 2000s by Qiagen improved detection, surpassing earlier skin tests.
Purpose: Measures interferon-gamma levels to diagnose tuberculosis, guides antibiotic therapy, and evaluates patients with chronic cough, aiming to manage infection.
Test Parameters: Interferon-gamma levels
Pretest Condition: No special preparation required. Collect whole blood. Report history of TB exposure.
Specimen: Whole Blood (specialized TB tubes, 3-5 mL); 4 mL whole blood in Na Heparin tube. Transport in a biohazard container.
Sample Stability at Room Temperature: 24 hours
Sample Stability at Refrigeration: 48 hours
Sample Stability at Frozen: Not recommended
Medical History: Document chronic cough or fever. Include current medications or TB history.
Consent: Written consent required, detailing the test's purpose, TB risks (e.g., active disease), and sample collection risks.
Procedural Considerations: Uses ELISA to measure interferon-gamma, requiring labs with plate readers. Results available in 2-3 days. Performed in labs with strict handling.
Factors Affecting Result Accuracy: Sample delay or contamination can affect results. Medications may alter levels, requiring correlation.
Clinical Significance: Positive result confirms TB infection, guiding therapy. Early treatment might prevent progression, while untreated cases lead to disease. Negative results may require chest X-ray.
Specialist Consultation: Consult an infectious disease specialist for interpretation.
Additional Supporting Tests: TB culture, chest X-ray, or sputum analysis to confirm diagnosis.
Test Limitations: Indicates exposure only; correlation with symptoms needed. False positives possible with prior BCG.
References: CDC Guidelines, 2023; American Journal of Respiratory and Critical Care Medicine, Andersen P, 2022.
