Performance of Quantiferon(®) for the diagnosis TB

The aim of the study was to evaluate the performance of Quantiferon Gold-In-Tube(®) (QFN) for the diagnosis of tuberculosis (TB) during hospitalization in an infectious diseases department.

QFN was performed in 245 patients recently hospitalized for suspected TB. Subsets of patients underwent tuberculin skin tests (TST), and microbiological cultures were performed.

TB was diagnosed in 57 (23%) patients: pulmonary in 23 (40%), extrapulmonary in 16 (28%), and disseminated in 18 (32%). Seventeen (30%) of these TB patients were immunocompromised, including 12 with HIV infection. The sensitivity of QFN was 74%, its specificity 56%, its positive predictive value 43% and negative predictive value (NPV) 92%. The sensitivity was similar in pulmonary and extrapulmonary TB but lower in disseminated TB, although not significantly so. The sensitivity was also lower (P=0.04) in immunocompromised patients. The specificity was lower in migrants than in native French patients (P=0.01), and lower in patients with a history of TB than in those without (P<0.001). Finally, combining culture with QFN significantly increased the sensitivity (P=0.008), and produced a higher NPV, as for the combination with TST, but not significantly different than with QFN alone.

The performance of QFN was weak in this context, especially in subgroups at high risk for latent TB. However, combined negative results of QFN or TST and culture could be useful to rule out active TB.