Spanish HCWs and IGRA

This head-to-head study (Evaluation of Interferon-Gamma Release Assays in the Diagnosis of Recent Tuberculosis Infection in Health Care Workers) has a fairly predictable outcome with a twist

IFN-γ tests are a useful tool for detecting recent infection in HCWs population,

the twist being recent infections. Whilst IGRAs are not affected by prior BCG vaccination (and the number of BCG vaccinated people can be fairly easily determined) this study showed that the TST was also picking up past infections in non BCG vaccinated people who were TST+ and IGRA-

the results suggested that in the 20% of cases these individuals were infected in the past.

This is a significant number and probably means that the TST is reacting to memory T cells in all people, not just those who are BCG vaccinated.

The implication is that IGRA's enhanced capabilities are applicable to both BCG and non BCG vaccinated populations. This was the experience of the Cincinatti study which found that

QFT-G and QFT-GIT are clinically and economically worthwhile alternatives to TST and should be considered in screening non-BCG and BCG vaccinated HCWs for LTBI

.