Test Your Knowledge Answer #401

 

The accuracy of self-monitoring of blood glucose (SMBG) is critical for successful basal-bolus therapy. Frequent SMBG, careful carbohydrate counting, and appropriate dosage adjustments based on these variables limit the duration and magnitude of glycemic exposure and decrease the risk of hypoglycemia. The United States Food and Drug Administration requires all meters to have an error rate of less than 20%, and the American Diabetes Association recommends an error rate of less than 10%. Most blood glucose meters are accurate when used according to the manufacturer's guidelines. User error is the primary cause of inaccurate SMBG. In this case, the patient's technique was not at fault. Because blood glucose meters can lose accuracy over time, comparing the meter blood glucose measurement with a laboratory measurement is the most efficacious way to assess a potential error.

 

The laboratory hemoglobin A1C measurement is rarely incorrect because most clinical laboratories calibrate machines on a daily basis. Occasionally, a blood sample might be mislabeled, which would lead to an erroneous measurement. In this patient, however, there is no indication that the A1C value is incorrect because it is consistent with both of the measurements obtained at the last visit.

 

Whereas the A1C value indicates the average blood glucose level over the previous 2 to 3 months, the fructosamine (also known as glycated albumin) level indicates the level of glycemic control over a shorter period of time (2 to 3 weeks).

 

Fructosamine levels may be more accurate than A1C levels in persons who have anemia or who have a hemoglobinopathy (such as sickle-cell disease). A fructosamine level would not be expected to yield any additional, clinically useful information in this case. Although alternate-site testing does offer a potentially less painful way to perform SMBG, it is only as accurate as the meter and the meter operator. Ongoing diabetes self-management training is an essential component of diabetes care and should include an assessment of SMBG technique. However, in this case, the patient's SMBG technique was deemed good, and she has successfully implemented her current basal-bolus regimen for 2 years.

 

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