Abstract

BACKGROUND AND OBJECTIVE:

To evaluate the performance and the usefulness of an in vitro interferon gamma release assay in the diagnosis of latent tuberculosis infection in immunocompromised hospital-based population.

PATIENTS AND METHOD:

A cohort of 445 high-risk adults from a hospital located in an intermediate tuberculosis burden area were prospectively evaluated for latent tuberculosis by means of the whole blood in vitro QuantiFERON-TB Gold assay (QTF), measuring tuberculosis-specific interferon gamma release by memory-effector T lymphocytes.

RESULTS:

Overall the test displayed a positive result in 15.43% patients. Among the different risk groups, hemodialysis patients revealed the highest positive rates (30.23%). Indeterminate results (10.19% on the whole) were more often seen in neoplastic (18.03%) patients and in patients with autoimmune disease (17%). In 291 patients in whom QTF and Mantoux were simultaneously performed, concordance was moderate (kappa = 0.4520) with a 76.8% agreement when Mantoux was negative (179/233) but reaching only 50% (29/58) when Mantoux positive patients were selected.

CONCLUSIONS:

QFT test is suitable for routine latent tuberculosis diagnosis in hospital-based immunocompromised patients. At least in some of them, i.e. hemodialysis and patients with autoimmune suppression, QFT adds valuable information for therapeutical decision-making. In Mantoux positive patients, it is very useful for ruling-out false positives due to BCG-vaccination and/or non-tuberculous mycobacterial infection.