Question:
For monitoring long-term control of diabetes mellitus, is checking
hemoglobin (HbA1c) more important than fasting or postprandial glucose
levels? What are the factors affecting HbA1c levels?
Answer:
"Although HbA1c may be lowered by rapid erythrocyte turnover and is
altered in certain hemoglobinopathies, it provides an excellent tool for
assessing overall glycemic status. However, several caveats to the
acceptance of HbA1c as an absolute guide to the level of control of a
given patient have been recently recognized.
Of interest, in patients with diabetes, the prandial glucose level is
more strongly correlated with HbA1c than is the fasting glucose
level.[2] Population studies provide strong evidence that the 2-hour
postchallenge glucose level is more strongly related to mortality than
the fasting level.[3] The risk of microvascular end points also
increases with postload glycemia levels.[4] The potential adverse
effects of postprandial hyperglycemia include increased glomerular
filtration rate and renal plasma flow, increased retinal blood flow,
impaired endothelial vasodilation, increased procoagulative processes,
and increased oxidative stress.
Thus, although HbA1c is currently the principal tool for assessing
glycemic status, one must continue to measure fasting and, particularly,
postprandial glucose levels, in the determination of individual glycemic
risk."
