Stephen J.LurieMD, PhD, Senior EditorIndividualAuthor
To the Editor: Dr Mazurek and colleagues1 claim that the IFN-γ assay used in their
study was comparable with the purified protein derivative (PPD) skin test
in its ability to detect latent tuberculosis but was less affected by BCG
vaccination. The study, however, has several methodological deficits and needs
to be interpreted with caution.
First, it is surprising that immunocompromised individuals were excluded
from the study although they are at higher risk of mycobacterial infections.2 Second, 18% of patients with suspected tuberculosis
(group 3) had a negative IFN-γ assay and a positive TST result while
only 3% had a positive IFN-γ assay and a negative TST result. This calls
into question the "higher sensitivity" of the assay.
Herzmann C. Interferon Assay Compared to Tuberculin Skin Testing for Latent Tuberculosis Detection. JAMA. 2002;287(4):450-452. doi:10.1001/jama.287.4.447