Has anyone ever heard of one lab having substantially different hemoglobin A1c results than other(s)?
This is going to sound crazy, and maybe I'm grasping at straws here, but I went to a new lab for the first time ever a little over three months ago. (My endo used to be able to just send me downstairs to the blood lab in the hospital where he practices, and my gp has done the same at his own facility when I go in for a complete annual physical, but my insurance company is now only reimbursing for bloodwork at one chain of labs.) At that time, my A1c was over 9.0. I've gone back over my records and I have not had a result over 8.0 in years, and no higher than the low 7s in at least two years.
I know some would say that all of those numbers are way too high, but I try (for the record, I have had some A1cs in the 6s in the past year or two). Even from a statistical perspective, a deviance of 1.5-2 sounds significant to me. So, I was concerned, but I decided not to freak out and just give it another three months and see what happened with my next A1c. Well, when I went back to my endo (and subsequently to the same lab) last week, this time, it was 8.9.
Aside from being kind of frightened, I'm also really at a loss because I honestly can't think of anything I'm doing differently. I test far more than 4 times a day - the numbers may not be perfect, but they've been in line with where they've been for the past few years. According to that estimated average glucose table that ADA put out a few years back, these numbers would suggest that my blood sugar has typically been over 200 for the past 6 months, and that doesn't sound right. Granted, I don't use CGM, so it's possible I'm having more highs at random times that I'm not aware, but it's not as though my blood sugar could come back down very far magically on its own, right?
Even weirder, though, is that my doctor happened to mention that this new lab indicated (I guess in the report?) that they consider under 9.0 to be the target for the A1c. I presume that means the target for those of us with (T1) diabetes, not the general population, but even so, I've never heard anyone use a number anywhere near that high as a benchmark. My endo certainly did not agree with the lab's recs. (I didn't actually talk to him - I called him back when I got his voicemail, but he didn't have a chance to get back to me by close of business, but he mentioned what he considered to be a target A1c in his message, as if I needed the reminder.)
Well, I'm definitely not going back to that particular lab again, in any case, if only out of superstition - at least there are plenty of other locations in network, for all the good it may do since they're all owned by the same company - but is it possible that there's a logical explanation? Other than the obvious, that is...that any semblance of control over my blood sugar is slipping through my fingers? Is it possible that this new lab I went to really is doing some kind of quirky version of the A1c that should be expected to generate higher results? Has anyone ever heard of anything like this? I will ask my doctor the same thing, but I couldn't wait until he calls me back tomorrow without at least trying to get some answers tonight.
PS: Apologies if this shows up as one long block of text with no paragraphs. Not sure what is wrong with the board tonight - it looked like some sort of mid-90s basic HTML website (or like it wasn't done loading) when I logged in, but I was able to post and in too much of a rush to do so to care. Unfortunately, it posted with no paragraph breaks on my first attempt. I tried manually inserting tags for line breaks...we'll see if that works. I know it sounds like I'm just blaming technology for my own failings left and right tonight...maybe I am...
PPS: ETA: Mystery solved, possibly? Apparently there is a test called "total glycohemoglobin," which is different than the A1c. I'm embarrassed to admit I never knew what the A1c actually stood for, but apparently it's only one type of hemoglobin to which glucose bonds; for some reason, it's considered the most precise measure of average blood glucose level. The lab that I was so critical of is actually surprisingly transparent, insofar as making their menu of blood tests available on their website to the general public. In their system, the total GHB test has a different code than the HbA1c test; they list normal HbA1c for a diabetic adult as less than 7.0, and normal total GHB for a diabetic adult as less than 9.0, which was the figure my dr quoted in his message. I'm thinking the lab maybe the lab has a confusing form (HbA1c is frequently referred to as just glycohemoglobin/glycated hemoglobin) and my endo, not being used to it, was referring to the wrong test when he gave me my results? Well, I guess I'll find out tomorrow...
Hopefully you figured out the problem, between the HbA1c and GHB.
I have had slightly different results between a lab HbA1c and a little finger prick one they did in my local doctor's office. I'd gone through my meter and averaged my test results and came up with average of 160, which is right on track with the 6.7 A1c I've had for years. But when the doctor did the in-office test the result came back as 6.3. I was surprised because my overall control, medications, weight, and lifestyle were the same. About a month later I went to the endo and had a lab drawn-- A1c was a 6.7.
Thanks. Well, apparently my doctor really did mistakently order that other test, the "total" glycated hemoglobin/glycosylated hemoglobin/glycohemoglobin test, and that was the result that he was referring to, both this time and three months ago. And the results really are typically ~ 2.0 higher than the hemoglobin A1c test. And apparently both of those last two results I got have been within range for this other test (I seemed to remember that the last one had been over 9.0, but I was so demoralized at the time that I don't seem to have written it down...according to my dr's files, though, that one was under 9.0, as well, the standard for diabetic adults in this test). Under other circumstances, two glucose/hemoglobin tests in a row below the recommended max would be something I would consider cause for celebration, but...
Among other things, I'm not sure how reliable those results are - does anyone remember this total GHB test? My endo had never heard of it. One website, for some chain of labs that still had a notice from 1999 available for download, said the A1c and GHB tests were comparable in their accuracy but they were phasing out the total GHB test because they didn't want to cause confusion with the A1c test results (I have to say I approve of that decision, after the past 24+ hours!). But another site I stumbled across claimed that the amount of glucose that bonds with the A1c hemoglobin molecules is more telling of blood sugar control than the total GHB, and that was why the A1c ultimately became the standard. It feels weird not to have had an A1c test in over 6 months...
I have to say I'm also really annoyed at my doctor - not just for ordering the wrong test, but for not even thinking twice when it seemed my A1c was suddenly 1.5-2.0 higher than it had been in years! And conveying that info in a voicemail message? Sheesh! I almost switched endos a while back (based on a referral I got on this site, actually) but by that point the dr who came so highly recommended was not taking new patients with my insurance. At this point, though, I'm wondering if just about anyone who knows how to order/read a lab report correctly would be an improvement...