CHICAGO — Self-monitoring of blood glucose did not significantly improve hemoglobin A1c levels in a trial of patients with type 2 diabetes not receiving insulin.
“Although patients with type 1 and insulin-treated type 2 diabetes benefit from self-monitoring, this trial does not provide convincing evidence of benefit in non-insulin-treated type 2 diabetes,” lead researcher Dr. Andrew J. Farmer said at the annual scientific sessions of the American Diabetes Association. His team conducted the trial, known as DiGEM (Diabetes Glycaemic Education and Monitoring).
Health costs and quality of life data have yet to be presented from the three-arm, randomized, parallel group trial of 453 patients managed in U.K. general practices with diet and oral hypoglycemic agents alone.
“In the meantime, the results do not support recommendations for routine self-monitoring of blood glucose in reasonably well-controlled patients with type 2 diabetes,” said Dr. Farmer, division of public health, University of Oxford (England).
The trial had an 80% power at a 5% level of significance to detect the primary outcome—a change in hemoglobin A1c of 0.5 percentage points—among three groups. Patients were randomized to a control group with no blood glucose monitors and 3 monthly hemoglobin A1c measurements; a less intensive self-monitoring group with the results interpreted by a nurse practitioner in addition to usual care; and a more intensive self-monitoring group that was given the usual care plus training in interpreting and applying the results in relation to diet, physical exercise, and medication regimens.
Patients in the more intensive group had more latitude regarding when they could test their glucose, and averaged 6–7 tests per week. Those in the less intensive group were told to use their meters before meals and averaged 5–6 tests per week, Dr. Farmer explained.
There were 152 in the control group, 150 in the less intensive self-monitoring group, and 151 in the more intensive self-monitoring group.
At admission, the average duration of diabetes was 3 years, and the mean HbA1c was 7.5%. Overall, 67.5%–73% of patients in each of the groups had had no prior experience with self monitoring.
At 12 months, the mean HbA1c value was 0.14 percentage points lower in the less intensive self-monitoring group than in the control group, and 0.17 percentage points lower in the more intensive self-monitoring group than in the control group. The differences between groups were not statistically significant.
Among secondary outcomes, there were no significant differences between groups in blood pressure control. Surprisingly, there was a significant difference between groups in change from baseline of total cholesterol, with a decrease of 0.14 mmol/L in the control group, 5.2 mmol/L in the less intensive group, and 5.4 mmol/L in the more intensive group.
Hypoglycemia was reported by patients in all three arms of the trial, with the number of reports significantly higher in the self-monitoring groups than in the control group. This finding may be attributable to increased awareness of low blood glucose more than a true biochemical difference arising from the use of the monitor, Dr. Farmer said.
Over the 12 months of the trial, between one-third and one-half of patients stopped using their monitors. In all, 57 patients (13%) were lost to follow-up.
Dr. Farmer speculated that for many patients, the small day-to-day improvement in glucose results may have been obscured by the measurement variation from day to day, and may have contributed to the reason some people gave up. “It's well recognized that, in some people, when the readings don't vary—or seem uninterpretable—[there is] a loss of motivation,” he said.
Interpretation of the DiGEM data will be hotly debated, in part because of the financial implications of self-monitoring on health care agencies and insurers.
The study moves the field ahead, but leaves some questions unanswered, Dr. Bernard Zinman, director of diabetes care at Mount Sinai Hospital, Toronto, said in an interview.
“This study proves definitively that self-monitoring of blood glucose does not seem to have an impact on changing an individual's lifestyle … and therefore [on improving] control,” Dr. Zinman said.
But he added that the investigation didn't address the question of whether, “if you give patients instructions on how to modify their oral hypoglycemia or give their physicians the opportunity to modify [it], self-monitoring of blood glucose may be very valuable in this population.”