IMO the mistake was using the test in isolation without considering other criteria. Let’s say you have somebody in a village who travels to visit a clinic. Chest xray positive so sputum samples taken. They don’t convert for 3 weeks, but contact is lost with patient. Maybe in this scenario the blood test adds the additional factor needed to start treatment sooner.

There’s a lot of other diseases there a blood test can diagnose immediately, and I don’t blame health workers for the confusion, quantiferon is a unique test, but a countrywide education campaign could have worked to keep it as part of the diagnostic tools.