ILLUSTRATIVE CASE
Two weeks ago, you informed your patient—a 53-year-old man with a body mass index of 28.4—that he has type 2 diabetes. Since then, he has seen a nutritionist and begun exercising regularly. His hemoglobin A1c (HbA1c) is 7.7%. You recommend that he begin taking metformin. The patient is worried about the potential for oral antidiabetic agents to cause hypoglycemia. He’s aware that many patients with diabetes monitor their blood sugar levels at home and wants to know if he should, too. You wonder whether it’s necessary, or even advisable, to initiate self-monitoring at this time.
For patients with type 2 diabetes, self-monitoring of blood glucose makes intuitive sense. Theoretically, it reinforces self-management behaviors, promotes adherence to the prescribed medication regimen, and leads to better glucose control. It seems obvious, too, that patients taking medications intended to lower blood sugar need to be aware of their glucose levels so they can take action to reduce the risk of complications.
But things that make sense intuitively do not always stand up to scrutiny. New high-quality evidence suggests that for those with newly diagnosed diabetes, self-monitoring of blood glucose may do more harm than good.
More questions than answers
While it is generally accepted that glucose self-monitoring is useful for those with insulin-treated type 2 diabetes,2-4 evidence supporting the practice for patients with diabetes who do not require insulin is limited. Two recent meta-analyses of RCTs5,6 found that self-monitoring of blood glucose achieves a statistically significant reduction of 0.4% in HbA1c; the quality of the studies, however, was limited. A well-designed RCT was needed, the researchers concluded, to settle questions about the value of self-monitoring.
The most recent Cochrane review7 of self-monitoring reached a similar conclusion: The reviewers called for additional research into the benefits of self-monitoring for patients with diabetes who do not need insulin. The reviewers also emphasized the need for information on patient-related outcomes such as quality of life, well-being, and satisfaction.
Are recommendations out of step?
Despite the lack of definitive evidence, the Department of Health and Human Services calls on us to increase the proportion of patients with diabetes who monitor their blood sugar at least once daily to 60% as part of its Healthy People 2010 initiative.8 The American Diabetes Association states that self-monitoring of blood glucose may help patients taking oral antidiabetic agents achieve glycemic goals.9 And the International Diabetes Federation recommends that self-monitoring of blood glucose be offered to all people with type 2 diabetes taking insulin or oral agents—and be part of the patient education that is given to all those who are newly diagnosed.10
But all of these groups may need to rethink their recommendations in light of the latest findings from the O’Kane RCT.
STUDY SUMMARY: Self-monitoring has little effect on glycemic control
O’Kane and colleagues conducted a prospective RCT comparing self-monitoring versus no monitoring among 184 people with newly diagnosed type 2 diabetes.1 Patients were randomized to the self-monitoring or control group for 1 year, with clinic visits at 3-month intervals. Those who were already taking insulin or had engaged in self-monitoring of blood glucose were excluded.
At baseline, there was no significant difference in HbA1c, age, or sex between the 2 groups. Participants in both groups underwent identical diabetes education programs throughout the study period and received dietary and medical management based on the same treatment algorithm. Patients whose baseline HbA1c was >7.5% received metformin, followed by the sulfonylurea gliclazide if they did not reach target at the maximum dose of metformin. There was no significant difference in medication use at baseline or at 12 months.
Patients in the self-monitoring group were given glucose monitors and asked to record 4 fasting and 4 postprandial capillary blood glucose measurements per week. They were also taught to monitor and interpret blood glucose readings, and to respond appropriately to high or low readings.
At each follow-up visit, patients underwent blood tests for HbA1c, lipids, and electrolyte levels and completed questionnaires about treatment satisfaction, attitudes about diabetes, and levels of depression, anxiety, and well-being. Adherence to self-monitoring was verified by downloading meter readings. The dropout rate was low (2.2%), and adherence in the self-monitoring group was high. Study results were assessed using intent-to-treat analysis.
HbA1c fell in both the self-monitoring and control groups, with no significant differences at any point. The mean (standard deviation) value at 12 months was 6.9% (0.8%) in the self-monitoring group, compared to 6.9% (1.2%) in the control group, with a 95% confidence interval for the change in HbA1c of –0.25% to 0.38%. Throughout the study period, there was no difference in use of oral hypoglycemic medications or reported hypoglycemia.
