The intensity of QuantiFERON TB-gold response does not differentiate active from latent tuberculosis.

We analyzed positive QuantiFERON (QFT) assays, performed between July 2009 and April 2011 in the Mercy University Hospital, Cork, Ireland, which included, 94 patients with latent tuberculosis (LTBI) and 35 patients with active tuberculosis. There was no difference in the intensity of response between patients with LTBI and active tuberculosis (p = 0.1589). In patients with LTBI, there were no correlations between age (p = 0.353), sex (p = 0.476), smoking (p = 0.323), contact (p = 0.612), Mantoux response (p = 0.055), Irish nationality (p=0.768), previous BCG vaccination (p = 0.504), WCC (p = 0.187), lymphocyte count (p = 0.786), neutrophil count (p = 0.157) and the intensity of QFT response. Similarly in patients with active TB, there were no correlations between these variables and QFT response. The intensity of QFT response does not help to differentiate active from LTBI. The intensity of QFT response is not influenced by age, sex, smoking, remoteness of contact history, Mantoux response, nationality, CXR abnormalities, BCG vaccination and peripheral lymphocyte count.