Comparison of a QuantiFERON-TB gold in tube test with tuberculin Skin test in patients with active and latent tuberculosis infection

Tuberculosis (TB) is an important infectious disease with high mortality and morbidity worldwide. The tuberculin skin test (TST) is known as the first immonologic diagnostic method in TB. TST has limited value for diagnosis of TB in different settings. There are some studies demonstrated that recently developed some serological tests such as Quanti FERON-TB Gold (QFT-GIT) test had greater diagnostic specificity than TST. The aim of our study was to compare the usefulness and the performance of QFT-G assays and TST in patients with active and latent TB disease.Sixteen patients with active tuberculosis, 26 patients with latent TB ve 21 controls were included into the study. The diagnosis of active TB was based on presence of at least one positive sputum smear and positive TB culture. Blood samples were taken for QFT-GIT before the treatment in patients with active TB and then TST was performed.There was no difference according to age and gender among groups (p ? 0.05). In 8 (50%) patients with active TB mean enduration of TST was under 15mm. Mean enduration of TST was significantly greater in latent TB patients than those of active TB patients (p:0.001) and in active TB patients it was higher than those of controls (p:0.001). QFT-GIT test was found to be significantly higher in active TB patients and in latent TB patients compare to those of controls (respective p:0.003, p:0.005). QFT-GIT tests were positive in 12 (%75.0) of active TB patients, in 15 (%65.2) of latent TB patients and in 3 (%14.3) controls. Sensitivities of QFT-G were found to be as 75% and specificities 85.7 % for active TB and 65.2 % and 85.7 % respectively for latent TB. When patients with active and latent TB were evaluated sensitivities of QFT-GIT were 75% and specificities 34.8 %. A positive correlation was detected between QFT-GIT test and TST.Even it was thought that QFT assays have the supplementary role for detection of active and latent TB, specificity of the test for the diagnostic discrimination between active TB and latent TB disease is low. QFT-GIT is not more valuable in the diagnosis of active pulmonary TB than TST especially in our country condition due to higher cost of QFT-GIT and presence of positive correlation between QFT-GIT ile TST.Key words: Active tuberculosis, latent tuberculosis, QuantiFERON-TB Gold IT, tuberculin skin test