It's a big pain, let me tell you. Fortunately, our medical forebears in this country did the leg-work to make a TB a rather rare disease, so I've only had maybe two cases in my career. It was a massive public health effort. I shudder to think how it would go over today.
I'm assuming that's two positives? I'm guessing you've seen more possible cases that require a negative test to rule it out. Probably someone traveling from a place where it's more common. Where the hospital does all the isolation, masks, etc until the test result comes back. Probably taking longer on a weekend for the result. Which, as you said, is negative more often.