Dr LoBue noted that they were constrained in forming decisions based on current studies
because this is limited by a really lack of good, large head-to-head comparison trials.
So this can be very biased by the fact that if you have one study which only looks at T-spot and one study that only looks at QuantiFERON, the populations may be so different that it’s really not fair to compare the sensitivity so I think you need to be very careful with that.That appears to be entirely reasonable; one would expect locations and populations to differ - such is the way with experiments conducted outside of the laboratory.
And to put it into a purely legal perspective if there isn't evidence the argument cannot be sustained and the claim should be dismissed.
However the CDC had previously changed the TB testing guidelines to only "testing among persons at high risk" involving risk analysis for each location and situation. Populations are assessed into groups and only those groups judged to be at risk, or are "special," are tested.
So what about special situations and populations that we’re interested in? Well, let’s start with contact investigations. So, if you look at the studies done in close contacts of patients with tuberculosis, what you tend to see is that the exposure characteristics associated with increased risk of infection tend to correlate better with IGRAs than they do with the TST.So it would appear that once populations are segregated into risk groups as per CDC guidelines IGRA are superior to TST. However, these guidelines were not helpful to the CDC review process
It’s not clear to us how they would affect applying this to a hospital which generally deals with low-risk people.Finding such a hospital may be difficult as hospitals dealing with low risk people, according to other CDC guidelines, would not necessarily test for TB.
Screening of low-risk persons and testing for administrative purposes (e.g., certification of school teachers) should be replaced by targeted testing.Following CDC guidelines may not always be easy
"If you test low-risk people, you're going to end up with a lot of false positives," explains Henry Blumberg, MD, hospital epidemiologist at Grady Memorial Hospital in Atlanta. "The idea is not to do repeated tests in low-risk situations."As advised by the CDC false positives are a latent condition of the TB skin test and using the TST is a risk .
Some persons may react to the TST even though they are not infected with M. tuberculosis.
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