The concept of diabetic control includes a feeling of well-being, avoidance of hypoglycemia and absence of ketoacidosis. It must also include an assessment of blood glucose levels. As mentioned above, a false assessment of the degree of control established can be made if this only includes the patient's own blood results. Measurement of HbA1c or total HbA1 must also be included when assessing control and is complementary to the patient's results. Normal self-monitored blood glucose results in the presence of elevated HbA1c usually imply either falsification of results, an inability to perform the test properly or a fault in the blood glucose meter, if one is being used.
Glycosylated (glycated) hemoglobin refers to a series of minor hemoglobin components formed by the adduction of glucose to normal adult hemoglobin. The usefulness of this measurement is that it reflects the integrated blood glucose concentration over a period that approximates the half-life of the red cell, 6-8 weeks. Although factors which affect red cell survival may invalidate this test, they are uncommon in clinical practice (except perhaps in patients of African-Caribbean origin).
Although measurement of HbA1c has become the gold standard in the assessment of diabetic control it may not accurately reflect the true level of excursions of glucose in the period studied. What HbA1c level should patients try to attain? Ideally, the answer is normality, but this is a counsel of perfection that may be associated with an unacceptably high risk of hypoglycemia. Levels of around 6% are certainly acceptable and patients should probably strive to maintain levels of < 7%. It is important to know the normal ranges for different laboratories (depending on the methodology used for measurement) before making comparisons between clinical centers. Ideally the normal range for HbA1c should be DCCT aligned.
Integrated glycemia over a much shorter period of time may be assessed by measurement of glycated proteins (fructosamine), although, because of uncertainty pertaining to its use, this assay has not become widely adopted.
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