QFT as a confirmatory test - FAIL

The Korean study is significant in that it deals with a large number from a relatively homogeneous group ie 7,109 classmates of contacts in which the rate of return was not a significant factor. The rationale to use QFT as a secondary test was because

we thought this would be the most cost-effective strategy. 

The only costs compared were

the reagent costs for QFT per person (US $20 to $30) and those for TST (approximately US $5).

Now consider the real life experience of the County of Los Angeles Department of Public Health where the cost of TST reagent per patient was $1.65/test, cost of labour etc $11.30/test and the amount of retesting required due to failure to return a staggering 50%.

Taking into account the added costs of treating TST false positives the true cost of diagnosing and treating 5,000 persons per year with the TST was calculated at ~$165,000 as compared with $109,000 using QuantiFERON.

The cost of reagent is the TST's only advantage.

Masae Kawamura makes the point that using QFT will not necessarily make TST better

The argument that a dual system is the most cost effective just does not hold water.