To Compare the Performance of Quanti-FERON with the Tuberculin Skin Test for Identifying Latent Tuberculosis Infection

Tuberculosis (TB) is an important issue which its control is still unsatisfactory at global level. Traditional diagnostic techniques for active TB diagnosis are inadequate: the diagnostic gold standard is the cultural exam which suffers from lengthy processing and requires highly specialized laboratories. Nowadays more specific tests have been recommended. The aim of this study is to evaluate the performance of Quanti FERON-TB (QFT)Gold In Tube-Test as a substitute for specific test tuberculin skin test for diagnosis of latent tuberculosis infection in high risk groups.

One hundred thirty four (134) individuals who worked in Bo-Ali hospital (Zahedan) enrolled in this study. They had no active tuberculosis. TST and QFT tests were performed. The cut-off point of TST was considered based on 15 (mm) or more indurations as positive. The result of QFT was evaluated by manufactured guidelines. Multivariate logistic regression was used to identify the putative risk factors of positive tests.

Proportion of employees with latent TB were 111(82.8%) were positive by either TST or QFT, and 76(56.7%) were positive by both tests. Agreement between the tests was high (73.8%, k=0.39; 95%CI: 0.21-0.44). Positive family history of Tuberculosis was significant risk factor for both positive tests.

This study showed high latent tuberculosis infection prevalence in hospital workers and high agreement between TST and QFT. Decision to select one of the tests will be depended on the population, purpose of study and availability of resources. The results revealed that the QFT can be appropriate alternative test for high risk group.