Tea for the taliban

When reviewing the Vinton study in the Australian Tuberculosis Review "JT" (Dr John Thompson, Canberra) said

It looks as if a negative QFT test will have to be followed by a TST and that 15 mm or more of induration will confirm infection.

As he has already acknowledged that QFT has a greater specificity it doesn't seem logical to then advocate the use of a less accurate test as a check. His rationale is

their (Vinton et al) conclusion does not match their findings that those staff in contact with a tuberculous patient are more likely to have a positive TST result.

which is at odds to what is actually written in the study;

For the TST, receipt of BCG vaccination, an occupation involving patient contact (as opposed to hospital occupations that do not involve such contact, eg, clerical positions), and a greater number of years lived in a high-prevalence country were associated with a positive test result.

What did limit the study was the poor follow up with TST;

117 (24.3%) of the 481 participants originally recruited did not have a TST performed and/or a TST result interpreted, and a large proportion of these individuals had had positive TST results in the past.

This failure to return makes the JT canvassed option of using the less accurate TST as a confirmatory test even sillier;

a strategy that combines the use of both the TST and the QFT–in tube test ... would result in increased cost without reducing any of the inherent problems of TST testing.

Writing in the QFT News March 2009 Cellestis made the following observations of the study;

The study correlated positive results to risk factors, such as country of birth, travel to high-risk areas, or high-risk occupation in the HCW setting, as well as BCG vaccination status.

...The authors concluded that a positive QFT result was associated with demographic and occupational risk factors such as birth in a high prevalence country, or an occupational contact. A positive TST result, on the other hand, was very highly associated with a prior history of BCG vaccination, far more than occupational exposure.

As Vinton et al conclude, the study

findings support the recent Centers for Disease Control and Prevention guidelines, which suggest that the QFT–in tube test is a viable alternative for a widespread HCW screening program

.