Dipeptidyl peptidase-4 (DPP-4) inhibitor add-on therapy is a new option for patients with inadequately controlled type 2 diabetes who are taking combined metformin and sulfonylurea (SU). We evaluated the efficacy and safety of this triple therapy and the characteristics of rapid responders and hypoglycemia-prone patients.

We included 807 patients with type 2 diabetes who were prescribed a newly added DPP-4 inhibitor to ongoing metformin and SU in 2009 to 2011. Glycemia and other metabolic parameters at baseline, 12, 24, and 52 weeks, as well as episodes of hypoglycemia were analyzed. Rapid responders were defined as patients with ≥25% reduction in glycosylated hemoglobin (HbA1c) within 12 weeks.

At baseline, while on the submaximal metformin and SU combination, the mean HbA1c level was 8.4%. Twelve weeks after initiation of DPP-4 inhibitor add-on, 269 patients (34.4%) achieved an HbA1c level ≤7%. Sixty-six patients (8.2%, 47 men) were rapid responders. The duration of diabetes was shorter in rapid responders, and their baseline fasting plasma glucose (FPG), HbA1c, C-peptide, and homeostasis model assessment of insulin resistance were significantly higher. Patients who experienced hypoglycemia after taking DPP-4 inhibitor add-on were more likely to be female, to have a lower body weight and lower triglyceride and FPG levels, and to have higher homeostasis model assessment of β-cells.

An oral hypoglycemic triple agent combination including a DPP-4 inhibitor was effective in patients with uncontrolled diabetes. Proactive dose reduction of SU should be considered when a DPP-4 inhibitor is added for rapid responders and hypoglycemia-prone patients.

We investigated whether patients' perceived glycemic control and self-reported diabetes self-care correlated with their actual glycemic control.

A survey was administered among patients with diabetes mellitus at an outpatient clinic with structured self-report questionnaires regarding perceived glycemic control and diabetes self-management. Actual glycemic control was defined as a change in glycated hemoglobin (A1C) or fasting plasma glucose (FPG) since the last clinic visit.

Patients who perceived their glycemic control as "improved" actually showed a mild but significant decrease in the mean A1C (-0.1%, P=0.02), and those who perceived glycemic control as "aggravated" had a significant increase in the mean FPG (10.5 mg/dL or 0.59 mmol/L, P=0.04) compared to the "stationary" group. However, one-half of patients falsely predicted their actual glycemic control status. Subjective assessment of diabetes self-care efforts, such as adherence to a diet regimen or physical activity, correlated positively with perceived glycemic control but showed no association with actual glycemic control.

Patients should be encouraged to assess and monitor diabetes self-care more objectively to motivate behavioral modifications and improve their actual glycemic control.