I'm certainly not even close to an expert, but since the Breathalyzer is used at my job all the time I figured I'd at least put my 2 cents out there. First and foremost (at least in my area) a Portable Breathalyzer Test (PBT) is not to be used as evidence to arrest someone for DUI. The roadside tests and/or any other major observations of the officer are what they use to do that and the PBT is more of just a guide for them and often may result in them being sent on their way with a ride. For example, if a person chooses to take the PBT and is just in the area of .08 BAC, the officer may not bring them back to the station for a Breathalyzer test if they believe their BAC to be falling as they may well be under the legal limit by the time they take the test. Also, the subject is legally entitled to take the matter up in court should they so choose and if their concerns have merit then they can get off. Beyond all that, I think it'd be out of the question to get a blood test for every DUI arrest and while probably imperfect, if the Breathalyzer is reliable to hold up in court I think it is far better than nothing.
Bottom line for me is that most of the examples the site gives seem to be extremely unlikely to land you with DUI charges on their own. Looking online, it appears that diabetes can only account for up to about .06 for instance, and it is policy to wait 20 minutes after having anything in your mouth (such as using an asthma inhaler) before giving the test as that is enough time for such confounding factors to dissipate. Also, most of the other stuff that might confound the machine aren't also going to provide law enforcement with probable cause to initiate a traffic stop or clues on a roadside test to make an arrest. So while the test may not be perfect or as accurate as a blood test, it is by far better than nothing and is the most reasonable option available at this time. Honestly, even a blood test is far from perfect as right now it usually takes longer to get a nurse to administer one, and in some areas they require the nurse to show up to court and testify for the results to be admissible (which they are not inclined to do).
So if it was just the test alone that lead to charges, some of these points might have merit. Since the lead up to the test involves giving law enforcement a reason to pull you over and reasons to arrest you before you even get to the test, then I think it's redundant enough to accept whatever risk of false positives may still exist to get the people off the road who put us all at risk with their bad judgement. Also, it's worth remembering that cops want their arrests to stick in court too and thus have all the incentive in the world to do everything leading up to the Breathalyzer as properly as possible. I know of some people that have gotten a bad reputation at court and among other LEOs for having their arrests overturned and believe me, it's not pleasant for them. In fact, losing credibility at court can actually put their careers at risk.
