Quantiferon-Gold Tuberculosis Test Cannot Detect Latent Tuberculosis in Patients With Leprosy

Area of Science:

• Immunology
• Infectious Diseases
• Mycobacteriology

Background:

• Leprosy, caused by Mycobacterium leprae, and tuberculosis, caused by Mycobacterium tuberculosis, are both mycobacterial infections.
• Latent tuberculosis infection (LTBI) diagnosis is crucial for effective management and prevention of active disease.
• Interferon-gamma release assays (IGRAs) like Quantiferon Gold (Q-G) are used to detect LTBI.

Purpose of the Study:

• To evaluate the performance of the Quantiferon Gold (Q-G) test in diagnosing latent tuberculosis in patients with leprosy.
• To investigate potential cross-reactivity issues between Mycobacterium leprae and Mycobacterium tuberculosis antigens used in Q-G testing.

Main Methods:

• The Q-G test was administered to 10 patients with paucibacillary leprosy and 40 patients with multibacillary leprosy.
• Chest X-rays were performed to assess for active tuberculosis.
• Results were analyzed to determine Q-G positivity rates and correlation with leprosy type and chest X-ray findings.

Main Results:

• Five out of 10 paucibacillary leprosy patients tested positive with Q-G, despite having negative chest X-rays.
• All 40 multibacillary leprosy patients tested negative with Q-G.
• Existing literature indicates 100% cross-reactivity between ESAT6 and CFP10 antigens (used in Q-G) for both Mycobacterium leprae and Mycobacterium tuberculosis.

Conclusions:

• The Q-G test demonstrated potential for false-positive results in paucibacillary leprosy patients due to cross-reactivity.
• The Q-G test is not a reliable tool for detecting latent tuberculosis in individuals with leprosy.
• Further research is needed to develop specific diagnostic methods for LTBI in leprosy patients.