Yet another study comparing QuantiFERON with TST, this time from Spain. Maybe it's me but I suspect that the medical science community speak in another language, perhaps exasperanto?
Starting off with the known knowns, they clearly state that
..it (QFT) has a higher specificity to LTBI than does the TST.Logically this would mean that a QFT negative has more weight than a TST negative however not so
the most problematic issue in our study was discordant results between the TST and the QFT-G test. Disagreement was present in 5% of HCWs for whom results of both tests were available.It seems fairly clear to me that if one test was more accurate than an other then there is a good chance that there would be disagreement between the two and when there is a disagreement the more accurate would be the obvious choice.
Even though the study was run over only 115 HCWs the same old no show was evident
In 8 HCWs (6%), the result of the TST was unknown because the HCWs did not return for evaluation.By any measure the final number tested was minimal. For the TST they read each result according to patient status
All TSTs that showed any induration were interpreted by the same physician. Induration of at least 5 mm in non–BCG-vaccinated HCWs or at least 15 mm in BCG-vaccinated HCWs was considered positive.Plus the same old double dip testing
In BCG-vaccinated HCWs, if the first TST was negative, a second TST was carried out 7–10 days later (TST in two stages), and the induration of the second TST was considered definitive.Despite expending considerable resources in identifying and chronicling the obvious handicaps of TST, in both operation and diagnosis, they were unable to form any conclusion that was meaningful
In any case, in the absence of long-term follow-up data, it could be too early to replace the TST with the QFT-G test for LTBI screening of HCWs.Mucho exasperante!
