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Background: Interferon-gamma release assays have emerged as a more specific alternative to the tuberculin skin test (TST) for detection of tuberculosis (TB) infection, especially in Bacille Calmette-Guérin (BCG) vaccinated people. We determined the prevalence of Mycobacterium tuberculosis infection by TST and QuantiFERON®-TB Gold In-Tube (QFT-GIT) and assessed agreement between the two test methods and factors associated with positivity in either test in Warao Amerindian children in Venezuela. Furthermore, progression to active TB disease was evaluated for up to 12 months. Methods: 163 HIV-negative childhood household contacts under 16 years of age were enrolled for TST, QFT-GIT and chest X-ray (CXR). Follow-up was performed at six and 12 months. Factors associated with TST and QFT-GIT positivity were studied using generalized estimation equations logistic regression models. Results: At baseline, the proportion of TST positive children was similar to the proportion of children with a positive QFT-GIT (47% vs. 42%, p = 0.12). Overall concordance between QFT-GIT and TST was substantial (kappa 0.76, 95% CI 0.46-1.06). Previous BCG vaccination was not associated with significantly increased positivity in either test (OR 0.68, 95% CI 0.32-1.5 for TST and OR 0.51, 95% CI 0.14-1.9 for QFT-GIT). Eleven children were diagnosed with active TB at baseline. QFT-GIT had a higher sensitivity for active TB (88%, 95% CI 47-98%) than TST (55%, 95% CI 24-83%) while specificities were similar (respectively 58% and 55%). Five initially asymptomatic childhood contacts progressed to active TB disease during follow-up. Conclusion: Replacement of TST by the QFT-GIT for detection of M. tuberculosis infection is not recommended in this resource-constrained setting as test results showed substantial concordance and TST positivity was not affected by previous BCG vaccination. The QFT-GIT had a higher sensitivity than the TST for the detection of TB disease. However, the value of the QFT-GIT as an adjunct in diagnosing TB disease is limited by a high variability in QFT-GIT results over time. [ABSTRACT FROM AUTHOR]

Two commercial serological tests, Pathozyme-TB complex plus and Pathozyme-Myco IgG, were evaluated for their sensitivity and specificity in HIV negative patients with serum samples from pulmonary tuberculosis (TB) patients and tuberculin positive, healthy controls. The sensitivity for the two tests was 50 and 80% respectively and the specificity 95 and 80%. With a prevalence of pulmonary TB of 10% in symptomatic patients who consult our laboratory, the positive predictive values (PPV) for the two ELISA tests were 92 and 80%, and the negative predictive values (NPV) 98 and 80% respectively. In the same patient group, the AFB smear has a PPV of 100% and a NPV of 97%. We conclude that AFB smear is a better mass screening tool than ELISA in symptomatic patients who consult our laboratory. The test could be useful as a complementary test in excluding or confirming TB in selected, smear negative, symptomatic patients with high degree of clinical suspicion of active TB.