When our daughter was very young, she had an almost perpetual cough. The doctor raised the possibility of cystic fibrosis and recommended that she be tested. CF makes sweat saltier, so the test back then (maybe still?) involved bundling the baby up in a warm room and carrying her around for an hour to make her sweat, then analyzing the sweat for salt content.
There was only one clinic that did this test, and they were booked three weeks out. During those three weeks, we managed to convince ourselves that all her symptoms pointed to CF. I wonder how many times we licked that poor kid and debated her saltiness. A very long three weeks.
At the end of the test both my daughter and I were drenched in sweat, she for obvious reasons and I from sheer anxiety. Then we waited around for the analysis. It was negative.