Which testing method is currently not validated or available for confirmatory testing of Tb?

The gamma interferon test, despite being valuable for screening latent tuberculosis infection (LTBI), is not considered a confirmatory test for active tuberculosis (TB) disease. It is used to identify individuals who may be infected with TB, but it does not indicate whether a person has active TB, which requires confirmation through microbiological testing or clinical evaluation.

The skin test, while also primarily used for detecting TB infection, serves a historical role in both screening and identification of latent TB rather than active disease confirmation. X-ray results can provide important clinical evidence when TB is suspected, and they often play a role in the diagnostic process, yet they are not definitive on their own without additional confirmatory testing. The latent TB infection test is designed to identify individuals who have been infected but does not confirm active pulmonary or extrapulmonary TB disease. Therefore, gamma interferon tests are specifically not used as confirmatory tests for TB, aligning with the question's focus.