Interferon-gamma-release assay prevents unnecessary tuberculosis therapy

Area of Science:

• Infectious Diseases
• Immunology
• Public Health

Background:

• Increased tuberculosis (TB) incidence in Israel due to immigration from endemic countries.
• Mandatory screening of TB patient contacts using tuberculin skin tests (TST).
• Consideration of prophylactic treatment for positive TST results.

Purpose of the Study:

• Assess the utility of interferon-gamma (IFNγ)-release assay (QFT-G) in preventing unnecessary anti-TB therapy.
• Evaluate QFT-G's role in managing suspected false-positive TST results with prolonged follow-up.

Main Methods:

• Performed QuantiFERON TB gold-in-tube test (QFT-G) on 278 individuals between 2008-2012.
• Included individuals who were mostly TST-positive and/or TB patient contacts.
• Correlated TST diameter with QFT-G results and followed QFT-G negative individuals.

Main Results:

• QFT-G was positive in 42% (72/171) of TST-positive individuals.
• No correlation observed between TST diameter and QFT-G positivity.
• 128 QFT-G negative individuals followed for 5 years showed no development of active TB.

Conclusions:

• A negative QFT-G test can obviate the need for anti-TB therapy in over half of TST-positive individuals.
• QFT-G demonstrates utility in identifying individuals who may not require prophylactic TB treatment.
• Supports the use of QFT-G for improved management of TB screening.