December 23, 2006
A1c (Glycohemoglobin, HgbA1c)
Question from Seoul, Korea:
Our 14 year old daughter, who is active and not overweight and has had type 1 for two and a half years, has been on the pump with NovoLog and Lantus for basal for five months after high A1cs with NovoLog injections and Lantus for a year. Her new blood glucose meter and Paradigm pump store lots of data and show amazingly good blood glucose control (near 130 mg/dl [7.2 mmol/L], with about five or six checks a day. We also random sampled all hours of nights and 60, 90, and 120 minutes after meals due to A1c above 10. But, even all the random samples show consistent blood sugars below 150 mg/dl [8.3 mmol/L], most between 120 mg/dl [6.7 mmol/L] and 138 mg/dl [7.7 mmol/L].
Her meter calibrates well when checked against other blood glucose meters. She is otherwise healthy, but very high quarterly A1Cs for a year mystify us. Every indication shows she covers her carbohydrates well with NovoLog, and her Lantus is working, too. She currently does have high blood sugars, over 240 mg/dl [13.3 mmol/L] due to stress, but can it skew the results that much? Her first DKA event last weekend due to forgetting her pump for a day included an A1c at the hospital of 16.7, followed two days later, also at the hospital, of 12.8.
Do you have any explanations for the high A1Cs that infer average blood sugars over 300 mg/dl [6.7 mmol/L] when virtually ALL the fingersticks show 115 mg/dl [6.4 mmol/L] to 140 mg/dl [7.8 mmol/L], taken randomly? I’d be glad to let an expert review her meter/pump data.
Answer:
It sounds like something is wrong with the A1c assay you are using. No A1c changes so dramatically within a few hours or a few days. I would change laboratories and see if the results change since your home monitoring does not match these high values. Sometimes, there is a hemoglobin variant which is non-pathological but interferes with the A1c assay. Another test to check is called fructosamine, which uses a completely different assay system and reflects shorter duration of glycemia than A1c hemoglobin.
Lastly, and not to be forgotten, are falsified blood glucose readings that are very common in children/teenagers so that the A1c values are, indeed, correct, but the home monitoring readings are the incorrect ones. This can be “solved” by direct observation of parents of all blood glucose tests for one to two months.
SB
