To the Editors:
I have read with interest several papers describing the use of cellular interferon (IFN)-γ-based blood tests, including the editorial by Davies and Drobniewski 1. Whilst reviewing the study by Lee et al. 2, Davies and Drobniewski 1 indicate that the T-SPOT.TB assay has higher sensitivity than QuantiFERON-TB Gold, but that the QuantiFERON-TB Gold may have better specificity.
I do not agree with this tentative conclusion as the study by Lee et al. 2 does not report the true specificity of the two tests, as the control group of 15- and 16-yr-old students used to examine the specificity of the assays, although healthy, had a defined risk of existing tuberculosis (TB) infection. This was acknowledged by Lee et …