Diagnosis of latent tuberculosis infection among HIV discordant partners using interferon gamma release assays

Area of Science:

• Infectious Diseases
• Immunology
• Public Health

Background:

• Limited data exists on how HIV status and CD4 counts affect Interferon-gamma Release Assays (IGRAs) for latent tuberculosis infection (LTBI) diagnosis.
• IGRAs, including QuantiFERON-TB Gold (QFT) and T-SPOT.TB (TSPOT), are crucial for LTBI screening.

Purpose of the Study:

• To assess the prevalence of and risk factors for positive LTBI diagnostic tests in HIV-discordant couples.
• To evaluate the performance of Tuberculin Skin Test (TST) and IGRAs in relation to HIV status and CD4 counts.

Main Methods:

• A cross-sectional study enrolled 596 individuals from 298 HIV-discordant couples in Zambia.
• LTBI diagnosis utilized TST, QFT, and TSPOT assays.
• Multivariate analysis identified independent predictors for positive test results.

Main Results:

• HIV-negative individuals were more likely to have positive TST, QFT, and TSPOT results compared to their HIV-positive partners.
• HIV-negative status independently predicted positive QFT and TSPOT results.
• Among HIV-positive individuals, CD4 counts ≥ 388 cells/μl were associated with positive TST and QFT, but not TSPOT.

Conclusions:

• Individuals with HIV showed significantly fewer positive LTBI diagnostic tests.
• Lower CD4 counts (< 388 cells/μl) were linked to reduced positive TST and QFT results, but not TSPOT.
• TSPOT may offer better performance than TST or QFT in HIV-positive populations.