Objective: The aim of the present study was to compare the of tuberculin skin test (TST) and Quantiferon-TB gold in Tube (QTF-GIT) test in diagnosis of latent tuberculosis infection in health care workers.
Methods: A total of 100 volunteers were recruited from the health care workers in our hospital. In addition to collection of descriptive data and occupational history including age, gender, occupation, duration of work, presence and number of BCG scars, also chest radiographs, QTF-GIT and TST were performed routinely in all participants.
Results: Rates of positivity for TST and QTF-GIT test were 42% and 23%, respectively and there was a weak concordance between these two companion diagnostic tests (k=0.23, concordance 62.2%). In comparison to TST, sensitivity and specificity of QTF were 35.7% and 86.2%. No significant correlation was detected between presence and number of Bacillus Calmette-Guérin (BCG) scars and QTF-GIT test. In contrast, as the number of BCG scar increased in accordance with the increase in the diameter of indurations in TST. Interestingly, there was a significant correlation between TST and QTF-GIT tests. The average diameter of TST in QTF-GIT negative individuals was 11 mm, while it was 15.4 mm in QTF-GIT positive cases. Positivity of QTF-GIT was more likely as the diameter of TST indurations increased.
Conclusion: We suggest that QTF-GIT test is an effective diagnostic measure for latent tuberculosis infection in countries that have high NTM prevalence and BCG vaccination ratios. However, further controlled studies on larger series are warranted to acquire more accurate results.