The clinical utility of tuberculin skin test and interferon-γ release assay in the diagnosis of active tuberculosis among young adults: a prospective observational study

We prospectively enrolled 166 young participants 20-29 years of age with suspected active TB in a military hospital of South Korea. The TST and QFT-IT were performed for all participants.Of the 143 patients included in the analysis, active TB was diagnosed in 100 (69.9%). There were 141 male patients, none of whom had immunosuppressive disease. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TST were 94% (95% CI, 87-98%), 88% (95% CI, 74-96%), 95% (95% CI, 88-98%), and 86% (95% CI, 72-94%), respectively. The sensitivity, specificity, PPV, and NPV of the QFT-IT were 93% (95% CI, 86-97%), 95% (95% CI, 81-99%), 98% (95% CI, 92-99%), and 84% (95% CI, 69-93%), respectively. No significant differences were found between the TST and QFT-IT in any statistic.Both the TST and QFT-IT showed high sensitivity and specificity in differentiating active TB from other diseases. The diagnostic accuracy of these two tests did not differ significantly when applied to this clinical population of young, immunocompetent adults in whom neonatal BCG vaccination was common, there was no history of previous TB and in whom suspicion of TB was high.ClinicalTrials.gov: NCT00982969Tuberculosis (TB) is an important public health problem worldwide. In 2007, there were 9.27 million cases of TB, and 1.3 million deaths occurred among HIV-negative TB cases [1]. South Korea has an intermediate TB burden; the incidence of new cases is 90 per 100 000 people per year despite an intensive effort for disease control [2]. A prompt and accurate diagnosis is critical for effective control and management of TB, but conventional diagnostic methods have their limitations. Completion of mycobacteria culture takes 3-8 weeks on solid medium and 7-21 days in liquid medium [3,4]. The sensitivity of acid-fast bacilli (AFB) smears is low [3]. The polymerase chain reaction test is often used for rapid microbiological diagnosis of TB, but its sensitivity for smear-negat