Swiss Medical Weekly have just published the
results of a study into the efficacy of QFT-GIT in haemodialysis patients.
We conclude that the QFT-GIT is a valid alternative to the TST. Together with the survey of TB risk factors, it may help to diagnose LTBI more accurately in HD-patients.
Importantly they acknowledge the difficulty in diagnosing a condition that has no symptoms
In the absence of a “gold standard” for the diagnosis of LTBI, it is impossible to determine the sensitivity or specificity directly within a given patient’s collective
However they found that a compromised immune system was no barrier
Although IGRA results are dependent on INF-γ production, the impaired INF-γ secretion in HD-patients does not affect the overall IGRA reliability
QFT-GIT compared well with risk factors
a positive result in the QFT-GIT appeared to be more closely correlated with previous TB-exposure (defined by suggestive chest X-ray findings, history of previous TB-disease, or immigration from a medium TB-prevalence region [25]) as a proxy for the test sensitivity.
TST less so
there are strong indications that IGRA sensitivity and specificity in HD-patients are higher compared to TST...
...IGRAs are a more reliable and powerful diagnostic tool than TST.
