Normal reference ranges use a 95 percent confidence interval, and that means that five percent of normal, healthy people will fall outside of that range. Calling these values abnormal is essentially a false positive, and because some of the companies that market tests to athletes use an even narrower reference range, that means they’re going to generate even more false positives. (They’re also, of course, incentivizing people to come back for retesting. Ka-ching!)
