February 18, 2002
A1c (Glycohemoglobin, HgbA1c)
Question from a physician in Oxford, Mississippi, USA:
I have a 71 year old male patient who was told that he had an elevated A1c and that he should monitor his blood glucose levels at home. In three weeks’ time, his level has yet to exceed 140 mg/dl [7.8 mmol/L] (even after meals). Are you currently aware of any specific factors that might result in a false positive A1c test?
Incidentally, his PSA level was recently tested (10.2) and a prostate biopsy was performed, which was completely clear. We are just curious whether A1c is affected by factors such as dietary supplements, hormonal imbalances, etc.
Answer:
There are several conditions which affect hemoglobin A1c measurement. levels. Increases can occur from negatively charged hemoglobins (HbF), uremia, alcoholism, lead, elevated triglycerides, increased bilirubin, opiates, chronic aspirin (large doses), and high-dose vitamin C. The amount of increase varies.
The cut-off of 140 140 mg/dl [7.8 mmol/L] by capillary blood determination may not be the best test. I would recommend an oral glucose tolerance test if there is any question.
JTL
