December 28, 2004
A1c (Glycohemoglobin, HgbA1c)
Question from New Jersey, USA:
I take metformin as part of my treatment for type 2 diabetes and have had fairly good control thus far. My last A1c was 5.8%. My blood sugar levels have been pretty good, 100 to 110 mg/dl [5.6 to 6.1 mmol/L] before breakfast/lunch/dinner and around 120 to 125 mg/dl [6.7 to 6.9 mmol/L] post meal, most of the time. Occasionally, it has gone to around 140 to 145 mg/dl [7.8 to 8.1 mmol/L] probably around three or four times in the last four months.
I tried the home A1c test using the Choice A1c Test Monitor and was surprised to see the A1c reading of 7.2%. I am not sure if these one time test machines are accurate, and, considering that I check my blood sugar at least four times a day and also have been pretty sure that they have been consistently at a good range, I am not sure what to make out of this A1c reading. What is your opinion of these tests? I was feeling absolutely good based on my sugar control and after this test, now I am feeling pretty low.
Answer:
These home A1c tests are not as good as the laboratory tests you get in most clinical laboratories. However, they should not be terribly off. For instance, they should test within 1% of the value. If you want to compare accuracy, you need to have the home test and the clinical lab test performed at the same time to determine their discrepancy. If it has been a while, you need to check your A1c. This test reflects control over the last three months. However, the test reflects an arithmatic mean and not a simple mean. That means that glucose control more recently is weighted heavier than what happened more distantly. Personally, I do not use the home tests. Our laboratory, where I work, has a state-of-the-art methodology and I would not substitute convenience for accuracy. Keep up the good work. If your numbers are as good as you say, they probably are a bit better.
JTL
