Background: Tuberculosis is one of the deadliest diseases over the world. Diagnosis of pulmonary TB
depends on combination various parameters. IGRA measure T cell release of IFN-γ in response to M.TB
antigen. WHO policy statement as on IGRA use in low and middle income countries is not established
yet. Objective: The present study aimed to compare between tuberculin skin test (TST) and interferon
gamma release assay (IGRA) in the diagnosis of active tuberculosis infection and study the effect of 3
months of first line anti-TB therapy on the positivity of the IGRA test.
Methods: 40 Egyptian patients were included in the study, and assigned as two groups; Group I
comprised 20 patients with negative sputum for AFB by Ziehl-Neelsen stains with positive sputum
culture for M.TB and Group II included 20 patients with positive sputum and Ziehl-Neelsen for AFB
before and after 3 months of first line of anti-TB therapy. All patients were subjected to full history
taking, clinical examination, X- ray chest, lab investigations, ESR measurements, microbiological tests
and ELISA measurement of Quantiferon-TB Gold.
Results: Lower significant values were found in group II after treatment than before treatment regarding
clinical parameters and 1st and 2nd hours ESR. IGRA test and TST showed sensitivity (91.18%, 76.4%),
specificity (83.33%, 66.67%), positive predictive value (96.88%, 92.86%), negative predictive value
(62.5%, 33.3%) and accuracy of (90%, 75%) respectively. IGRA results had no statistical significant
differences between the studied groups with poor agreement with TST ((κ) = 0.025).
Conclusion: IGRAS test had high sensitivity and specificity in diagnosis of active TB. More studies are
needed to evaluate the effect of anti-TB therapy on IGRA level.