Interferon-gamma release assay for detection of latent tuberculosis infection in casual and close contacts of tuberculosis cases

ABSTRACT

The tuberculin skin test [TST] has many limitations for the diagnosis of latent tuberculosis [TB] infection. The aim of this study in Egypt was to estimate the usefulness of an interferon-gamma release assay [IFN-gamma] assay for the detection of latent TB infection in contacts of active TB cases. A total of 116 participants were enrolled and divided into 3 groups community controls, casual [laboratory and clinic] contacts and close [household] contacts. Subjects diagnosed with latent TB infection by TST were 11.5% of controls, 71.1% of casual contacts and 29.6% of close contacts. Subjects diagnosed as latent TB infection by IFN-gamma assay [QuantiFERON-TB Gold In-Tube] were 5.9% of controls, 31.0% of casual contacts and 33.3% of close contacts. The overall agreement between TST and IFN-gamma was 66.7% [K= 0.28]. The IFN-gamma method could be more helpful than TST for detection of latent TB infection in contacts