Aim: Study degree of sensitivity and specificity of IFN-c as QuantiFERON-TB Gold
In-Tube assay in diagnosis of tuberculosis instead of tuberculin test.
Subjects and methods: Forty patients were included in this study subdivided into two groups.
First included 20 patients with sputum positive for tuberculosis, while the second included 20
patients suspected to catch TB infection, guided by: clinical and radiological examinations with
smear negative for TB. Control group included 10 clinical and radiological healthy controls previously
vaccinated by BCG with positive tuberculin test. All subjects were submitted for full clinical
history physical examination routine laboratory tests, plain chest X-ray, sputum study for acid fast
Bacilli by Ziehl–Neelsen stain, tuberculin test using Mantoux technique, sputum culture on Lowenstein-
Jensen Medium and QuantiFERON-TB Gold In-Tube (QFT-Gold IT) assay.
Results: QFT-Gold IT test sensitivity = 100% specificity = 100% predictive value positive
=100% which means that 100% of the disease positive patients gave positive QFT-Gold IT
test and predictive value negative =100% which means that 100% of the disease negative patients gave negative QFT-Gold IT test. Agreement between tuberculin test and QFT-Gold IT test was
good agreement where the ‘j’ was 0.65 (CI = 0.39–0.91). Study revealed positive correlation
between QuantiFERON level and severity of infection in sputum, which was statistically significant,
where ‘r’ was 0.92 and P-value was