No, it's genuinely a flawed test- in the guise used in the UK, different to most of the rest of the world, it is particularly hopeless. It's quite handy at picking out which farms have TB, if you've got a few cows with the disease it will hopefully find a proportion of them, but is limited when it comes to finding all of the ones with it.
Having said that, the guise we use in the UK compared to the rest of the world tends to take away far fewer false positives, if it says a reactor is a reactor then something like 99.97-99.99% chance she is... but if it says she's clear then we're much less certain of that. Of course, if we got rid of the avian injection at the top and just went off the bovine, they'd find more cows with TB, but they'd also take more that don't have it.
Not that the little furry things are helping matters, but how do we ever hope to get rid of it when we can't identify it in our cows properly?
i wish there were a better compromise, but it is at least fast and cheap. (gamma lab work alone costs £24 (?) per beast.)
And it has worked perfectly well on The Isle of Man -as far as i know- where there are (all together now) NO BADGERS.