I have a Kardia mobile device (it's attached to an Enron blood pressure machine so it can be set up to measure both blood pressure, heart rate and an EKG. I have paroxysmal A-fib and when I've checked my EKG when I suspected I was in A-fib, it's always read "possible" A-fib too.

I suspect the reason for that is a "CYA" move on the part of the company, they don't want a person diagnosing themselves with A-fib based solely on Kardia readings, so adding in the element of uncertainty in calling an EKG that shows even a typical A-fib pattern makes allowances for errors on the part of the operator, possible electrical interference or any other variable that may influence an EKG reading. There are disclaimers in the Kardia literature that state EKG readings should be verified with medical professionals to make a valid diagnosis of an arrhythmia like A-fib. It's my understanding that if you join Kardia's subscription service, sending them your EKG results allows for a medical professional to check those results and to interpret them. You'd get those results back as "Atrial Fibrillation", or whatever it is they could see in those EKGs. Sending your questionable EKGs like "possible A-Fib" to a professional, for instance, to your own doctor instead of the Kardia subscription service allows for their validation of the results you got from your Kardia mobile.

I recently had an interesting experience with this. I had an episode of A-fib late one night, my episodes usually last just a few seconds but this one went on and on. I decided to see if A-fib was what I was feeling, set up my Kardia, and sure enough, the heart rate was elevated with a result of "possible A-fib". I also have a pacemaker with a remote monitor that "rats" on me when those episodes come up, and I noted from looking at my patient portal at the cardiologist's office that the monitoring company had sent them a report with the date and time I was having this relatively prolonged A-fib episode. This report was outside the normal quarterly reports it sends, so it had to be reporting the A-fib episode.

Well, I printed out a copy of that A-fib episode I had picked up with my Kardia, to show it to the cardiologist during my recent appointment. He verified that they had gotten the report from the monitoring company showing a 2 hr+ long episode of A-fib and another one soon after lasting about an hour. He looked at the report from my Kardia, kind of laughed at the dates and times printed on it that were within the dates/times reported by the monitoring company, and said "yup, that's A-fib all right".

All-in all, I don't think the Kardia mobile calls an EKG for A-fib unless it meets all the criteria for A-fib, any question it's more likely to call it "unclassified", but there can be errors. So it's going to err on the side of caution, and add that element of uncertainty by calling it "possible" A-fib, which in any case of doubt should be verified with a professional. At least that is my take on it.