More on that LTBI bean counter study

Another aspect to the LTBI cost effectiveness study (previously discussed here) is the rate of return for the TST

We assumed that there will be a stringent follow up of contacts thus we used a return rate of 90%. In reality, up to 60% of individuals fail to return for their TST results [27, 28]

and they then admit that

At these lower return rates, single IGRA strategies become more cost-effective than their dual strategy counterparts.

Was there a cost given for the "stringent follow up of contacts?"

Whilst this study is primarily concerned with costs of contact tracing it is worth looking at TB screening in general. The rate of return was one of the factors that convinced Leeds Hospitals to switch over to QuantiFERON

in our view the fact that only one contact with healthcare services is required is a major benefit 

and the reality was that the dual strategy recommended by the others was not cost effective

we believe that using QFT blood testing followed by CXR is more effective and more cost-effective than NICE guideline 

Similarly in the HPA sponsored study conducted at a London Teaching Hospital the conclusion was that

For serial or subsequent testing of healthcare workers, the IGRA is a more appropriate test because it eliminates the need for a second visit and is not affected by interreader variability and previous bacille Calmette-Gue´rin vaccination.

You have to question the medical aspects of the LTBI study; despite their finding that

While the single IGRA screening strategies were the most costly, they were also the most effective at preventing cases of post-primary TB

they recommended a less effective strategy based, in part, on an assumption of costs.