Meta-analysis of individual patient data in randomised trials of self monitoring of blood glucose in people with non-insulin treated type 2 diabetes
Authors: A. J. Farmer, R. Perera, A. Ward, C. Heneghan, J. Oke, A. H. Barnett, M. B. Davidson, B. Guerci, V. Coates, U. Schwedes, S. O'Malley
Journal: BMJ (2012)

<b>Objective</b> To assess the effectiveness of self monitoring blood glucose levels in people with non-insulin treated type 2 diabetes compared with clinical management without self monitoring, and to explore the effects in specific patient groups. <b>Design</b> Meta-analysis based on individual participant data. <b>Data sources</b> Medline, Embase, and a recent systematic review of trials on self monitoring of blood glucose. Chief investigators of trials published since 2000 were approached for additional information and individual patient data. <b>Inclusion criteria</b> Randomised controlled trials in patients with non-insulin treated type 2 diabetes comparing an intervention using self monitoring of blood glucose with clinical management not using self monitoring. Trials published from 2000 with at least 80 participants were included. <b>Data collection </b>Individual patient data were collected from electronic files and checked for integrity. <b>Analysis</b> All randomised participants were analysed using the intention to treat principle. A random effects model of complete cases was used to assess efficacy, a sensitivity analysis comprised imputed data, and prespecified subgroup analyses were carried out for age, sex, previous use of self monitoring, duration of diabetes, and levels of glycated haemoglobin (HbA<sub>1c</sub>) at baseline. <b>Results</b> 2552 patients were randomised in the six included trials. A mean reduction in HbA<sub>1c</sub> level of −2.7 mmol/mol (95% confidence interval −3.9 to −1.6; 0.25%) was observed for those using self monitoring of blood glucose levels compared with no self monitoring at six months. The mean reduction in HbA<sub>1c</sub> level between groups was 2.0 mmol/mol (3.2 to 0.8; 0.25%) at three months (five trials) and 2.5 mmol/mol (4.1 to 0.9; 0.35%) at 12 months (three trials). These estimates were unchanged after imputing missing data, and estimates of effect in trials with higher loss to follow-up or a possibility of co-intervention compared with those with lower loss to follow-up and no co-intervention did not differ significantly (P=0.21). The difference in HbA<sub>1c</sub> levels between groups was consistent across age, baseline HbA<sub>1c</sub> level, sex, and duration of diabetes, although the numbers of older and younger people and those with HbA<sub>1c</sub> levels &gt;86 mmol/mol (10%) were insufficient for interpretation. No changes occurred in systolic blood pressure (−0.2 mm Hg, 95% confidence interval −1.4 to 1.0), diastolic blood pressure (−0.1 mm Hg, −0.9 to 0.6), or total cholesterol level (−0.1 mol/L, 95% confidence interval −0.2 to 0.1). <b>Conclusions</b> Evidence from this meta-analysis of individual patient data was not convincing for a clinically meaningful effect of clinical management of non-insulin treated type 2 diabetes by self monitoring of blood glucose levels compared with management without self monitoring, although the difference in HbA<sub>1c</sub> level between groups was statistically significant. The difference in levels was consistent across subgroups defined by personal and clinical characteristics.