My son has had a few sweat tests so maybe I can help with some of the questions. What was explained to us is that it takes two positive sweats to diagnois cf because there is a possibility that the first one was incorrect. And then each hospital will want one done at their clinic because they don't trust each other's lab procedures. There are a few different sweat collection techniques but they all do the same things - I've seen coils done on one arm, pads done on one arm and pads done on two arms at once (got a separate result for each arm). Do push for genetic testing either way though, because the 53 is high enough to be a concern.