Tipping point in opinion

The furphy that *TB diagnostic guidelines need to be prudent by limiting IGRA testing to an almost unachievable window of ≤ 3 days after the TST has just been tipped on it's head; when French health specialists looked at the Cost-effectiveness of QuantiFERON®-TB test vs. tuberculin skin test in the diagnosis of latent tuberculosis infection they found that

In France, for the diagnosis of LTBI after close contact with TB, the TST is more expensive and less effective than QFT.  Although it is more expensive, QFT is more effective and cost-effective than TST+QFT under a wide range of realistic test performance scenarios.

Given that the TST is less cost effective there is now no logical reason to continue with its usage.

At some point TST camp followers should consider a tactical withdrawal to save further embarrassment.

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*UK NICE guidelines say

The specificity of interferon-gamma tests seemed better, and there was less potential for false positive results..

Economic modelling was undertaken with various strategies from no action to a two-step strategy with either TST followed by interferon-gamma testing, or serial interferon-gamma tests. Of these options, the model provided most support, on grounds of cost-effectiveness, for a two-step approach with an initial TST, followed by an interferon-gamma test to confirm positivity.