[Analysis of discordance between tuberculin test and QuantiFERON-TB® Gold In-Tube in studies of contacts]

Abstract

Background and objectives: Our objective is to compare the tuberculin skin test (TST) and the QuantiFERON-TB(®) Gold In-Tube (QFT) in the diagnosis of latent tuberculosis infection (LTI) in a population of contacts of patients with pulmonary tuberculosis, and to analyze the influence of different variables in the discordance.

Patients and method: From March 2008 to September 2010, among a population of 300,000 inhabitants of the Basque Country, we analyzed all contacts of patients with pulmonary tuberculosis. All patients underwent the TST and the value of QFT was measured. Sociodemographic variables and vaccination were examined and we analyzed the discordance between the 2 tests.

Results: Seven hundred and four were included in the study, with a mean age of 27 years. Of these, 397 were vaccinated, with similar proportion between native and foreign. Increasing the age to 59 years (odds ratio [OR] 10.53, P<.001), being foreign (OR 2.71, P=.02) and vaccination (OR 4.22, P<.001) were predictors of the discordance between a positive TST and negative QFT.

Conclusions: It seems that the QFT, alone or combined with the TST, is a safe method for the diagnosis of LTI and its use would contribute to a more specific selection of individuals who would need preventive treatment.