Characterization of QuantiFERON-TB-Plus results in latent tuberculosis infected patients with or without...

Area of Science:

• Immunology
• Infectious Diseases
• Rheumatology

Background:

• Screening for latent tuberculosis infection (LTBI) is crucial for patients with immune-mediated inflammatory diseases (IMID) initiating biologic therapies.
• QuantiFERON-TB-Plus (QFT-P) is an interferon-gamma release assay (IGRA) used for LTBI diagnosis, measuring responses in TB1 and TB2 tubes.

Purpose of the Study:

• To compare the QFT-P response in IMID patients with LTBI undergoing screening for new biologic therapy against LTBI subjects without IMID.
• To evaluate the utility of QFT-P in a specific clinical context requiring immunosuppressive treatment.

Main Methods:

• Prospective enrollment of 167 subjects: 61 with IMID and LTBI, and 106 without IMID but with LTBI.
• All participants were confirmed as mitogen-responders, ensuring assay validity.
• QFT-P testing was performed, measuring IFN-γ production after stimulation.

Main Results:

• IMID-LTBI patients exhibited significantly lower IFN-γ production compared to non-IMID LTBI subjects.
• A notable proportion of discordant results (6.5% in IMID-LTBI vs. 8% in non-IMID LTBI) were observed.
• Logistic regression indicated that IMID-LTBI patients had a higher probability of low IFN-γ results (≤0.7 IU/mL) for both TB1 (OR 3.32) and TB2 (OR 4.33) stimulation.

Conclusions:

• IMID-LTBI patients demonstrate a diminished IFN-γ response to QFT-P, with a higher frequency of results falling within the indeterminate or 'grey' zone.
• The observed IFN-γ response patterns were independent of prior IMID treatments.
• These findings are critical for refining LTBI screening protocols and interpreting QFT-P results in IMID patients commencing biologic therapy.