The Relationship between Self-Monitored Blood Glucose Values and Glycated haemoglobin in Insulin-treated Patients with Type 2 Diabetes

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Diabet. Med. 27, 589–592 (2010) Abstract Aims Self-monitoring of blood glucose (SMBG) is an important self-management tool for insulin-treated patients with Type 2 diabetes mellitus (T2DM). Its value in estimating glycaemic control in insulin-treated T2DM patients remains unclear. The relationship between glycated haemoglobin (HbA1c) and SMBG measures in T2DM patients treated with premixed insulin lispro mixtures or basal insulin glargine was examined. Methods HbA1c and plasma equivalent glucose (PGe) data derived from SMBG profiles were pooled from five randomized clinical trials of patients with T2DM on one or more oral glucose-lowering medication ± 0–2 insulin injections per day switching to insulin lispro mixtures (N = 317) or glargine (N = 306). Patients generated seven-point SMBG profiles three times in a 2-week period prior to each HbA1c measurement. Pearson’s correlation coefficients (r) were calculated for PGe values and HbA1c. Receiver–operating characteristic (ROC) curves determined the ability of sets of PGe to estimate HbA1c (< or > 7.0%). Results Mean ± standard deviation age was 57.5 ± 9.5 years, body mass index 31.3 ± 5.6 kg/m2, 52.5% were male and HbA1c overall was 7.4 ± 1.0% at end-point. Among individual SMBG measures, r for HbA1c ranged from 0.34 to 0.49. For means of two or more PGe measures, r for HbA1c ranged from 0.51 to 0.59. Correlations were similar for either regimen. ROC curves were consistent with the correlation data. Conclusions These data provide patients and clinicians information on the relationship between HbA1c and SMBG measurements in patients with T2DM, and support the value of frequent blood glucose measurements for assessing overall glycaemic control.