Tuberculin skin test versus interferon-gamma release assays for the diagnosis of tuberculosis infection

Objective: Accurate detection of latent tuberculosis infection (LTBI) is becoming increasingly important due to the increasing use of immunosuppressive medications and the human immunodeficiency epidemic, which have increased the risk for reactivation to active tuberculosis (TB) infection. LTBI is detected by tuberculin skin test (TST) and interferon-gamma release assays (IGRAs). The latter include T-SPOT (R). TB (Oxford Immunotec) and QuantiFERON (R)-TB Gold In-Tube (QFT-GIT; Cellestis). We examined the value of TST versus IGRAs in the diagnosis of TB infection by meta-analysis based on data derived from a systematic literature review. Methods: PubMed was searched for articles in English published between January 2010 and July 2012 in which TST and IGRA were performed simultaneously in individuals with and without active TB infection. A random effect model meta-analysis was performed to determine pooled sensitivity and specificity values for TST, T-SPOT. TB, and QFT-GIT. Owing to the absence of a gold standard for the diagnosis of LTBI, active TB infection was used as a surrogate for LTBI. Results: Nineteen studies were included. T-SPOT. TB was significantly more sensitive [90% (95% confidence interval: 85-95) versus 64% (46-81)] than TST. The specificity of T-SPOT. TB was higher than the specificity of TST, but there was overlap between confidence intervals [77% (68-85) versus 57% (41-72)]. QFT-GIT seemed to be more sensitive than TST [75% (61-86) versus 64% (48-78)] but similarly specific [71% (62-86) versus 70% (57-81)]. Conclusions: IGRAs, especially T-SPOT. TB, are more effective at detecting TB infection than TST. Despite their higher cost, they have added value and can be requested in addition to TST.