Self-monitoring of blood glucose in non-insulin treated patients with type 2 diabetes: a systematic review and meta-analysis

Objective: To assess the effect of self-monitoring of blood glucose (SMBG) on glycaemic control in non-insulin treated patients with type 2 diabetes by means of a systematic review and meta-analysis. Research design and methods: MEDLINE and the Cochrane Controlled Trials Register were searched from inception to January 2009 for randomised controlled trials comparing SMBG with non-SMBG or more frequent SMBG with less intensive SMBG. Electronic searches were supplemented by manual searching of reference lists and reviews. The comparison of SMBG with non-SMBG was the primary, the comparison of more frequent SMBG with less intensive SMBG the secondary analysis. Stratified analyses were performed to evaluate modifying factors. Main outcome measures: The primary endpoint was glycated haemoglobin A(1c) (HbA(1c)), secondary outcomes included fasting glucose and the occurrence of hypoglycaemia. Using random effects models a weighted mean difference (WMD) was calculated for HbA1c and a risk ratio (RR) was calculated for hypoglycaemia. Due to considerable heterogeneity, no combined estimate was computed for fasting glucose. Results: Fifteen trials (3270 patients) were included in the analyses. SMBG was associated with a larger reduction in HbA1c compared with non-SMBG (WMD -0.31%, 95% confidence interval -0.44 to -0.17). The beneficial effect associated with SMBG was not attenuated over longer follow-up. SMBG significantly increased the probability of detecting a hypoglycaemia (RR 2.10, 1.37 to 3.22). More frequent SMBG did not result in significant changes of HbA(1c) compared with less intensive SMBG (WMD -0.21%, 95% CI -0.57 to 0.15). Conclusions: SMBG compared with non-SMBG is associated with a significantly improved glycaemic control in non-insulin treated patients with type 2 diabetes. The added value of more frequent SMBG compared with less intensive SMBG remains uncertain.