Quantiferon-TB Gold (QQS)

Price: 90 د.ا

Quantiferon-TB Gold is a blood-based diagnostic assay for detecting latent tuberculosis infection (LTBI) and active tuberculosis (TB). By measuring interferon-gamma (IFN-γ) release from T-cells in response to specific Mycobacterium tuberculosis antigens, it offers a rapid and reliable alternative to the traditional tuberculin skin test (TST).

How It Works

1. Blood Collection
   – A single blood draw (no special preparation or fasting required).
2. Antigen Stimulation
   – Blood is incubated with TB-specific peptides (ESAT-6, CFP-10, TB7.7).
3. Cytokine Measurement
   – Activated T-cells secrete IFN-γ, which is quantified via ELISA.
4. Result Interpretation
   – Elevated IFN-γ levels indicate prior exposure or active infection.

Clinical Indications

• Latent TB Screening in:
  • Healthcare workers
  • Close contacts of TB cases
  • Immunocompromised individuals (e.g., HIV, chemotherapy)
• Active TB Supportive Diagnosis when combined with clinical and radiologic findings
• Treatment Monitoring to assess response to anti-TB therapy

Advantages

• Single Patient Visit: No return visit needed to “read” the test.
• High Specificity: ESAT-6/CFP-10 antigens minimize cross-reactivity with BCG vaccine or non-TB mycobacteria.
• Quantitative: Provides numerical IFN-γ values to monitor trends over time.

Limitations

• Cannot Differentiate between latent and active TB on its own.
• False Negatives may occur in severe immunosuppression.
• False Positives possible with non-tuberculous mycobacterial exposure.

Interpretation of Results

IFN-γ Level	Interpretation
Negative	No significant immune response detected; unlikely TB exposure
Indeterminate	Low mitogen control or high background; repeat testing recommended
Positive	Significant IFN-γ release; TB infection likely (latent or active)

Frequently Asked Questions

1. How accurate is the Quantiferon-TB Gold test?
   – Sensitivity ~80–90% for active TB; specificity >95% for LTBI in BCG-vaccinated populations.
2. Can a positive result progress to active TB?
   – A positive result indicates TB exposure but does not guarantee progression; clinical evaluation is essential.
3. How long until I get my results?
   – Results are typically available within 24–48 hours after the blood draw.
4. Is the test safe during pregnancy?
   – Yes—Quantiferon-TB Gold is considered safe for pregnant women.
5. What factors can affect test performance?
   – Immunosuppressive conditions (HIV, steroids), improper sample handling, and recent non-TB mycobacterial exposure.

Conclusion

Quantiferon-TB Gold (QQS) is a practical, accurate, and patient-friendly tool for detecting TB infection. By eliminating the need for a return visit and reducing cross-reactivity, it streamlines screening in high-risk groups. However, results must be integrated with clinical assessment, imaging, and microbiological studies to distinguish latent from active disease and guide appropriate management.

Medical Laboratory Professionals’ primary duty is the patients, placing their welfare above their own needs and desires thus ensuring that each patient receives the best service and the highest quality of care according to current standards of practice. High quality laboratory services are safe, effective, efficient, timely, equitable, and patient-centered. Medical Laboratory Professionals work with all patients and samples without regard to disease state, ethnicity, race, religion, or sexual orientation. Medical Laboratory Professionals prevent and avoid conflicts of interest that undermine the best interests of patients. Learn More