Background: Self-monitoring of blood glucose (SMBG) has been found to be effective for patients with type 1 diabetes and for patients with type 2 diabetes using insulin. There is much debate on the effectiveness of SMBG as a tool in the self-management for patients with type 2 diabetes who are not using insulin.
Objectives: To assess the effects of SMBG in patients with type 2 diabetes mellitus who are not using insulin.
Search methods: Multiple electronic bibliographic and ongoing trial databases were searched supplemented with handsearches of references of retrieved articles (date of last search: 07 July 2011).
Selection criteria: Randomised controlled trials investigating the effects of SMBG compared with usual care, self-monitoring of urine glucose (SMUG) or both in patients with type 2 diabetes who where not using insulin. Studies that used glycosylated haemoglobin A(1c) (HbA(1c)) as primary outcome were eligible for inclusion.
Data collection and analysis: Two authors independently extracted data from included studies and evaluated the studies' risk of bias. Data from the studies were compared to decide whether they were sufficiently homogeneous to pool in a meta-analysis. Primary outcomes were HbA(1c), health-related quality of life, well-being and patient satisfaction. Secondary outcomes were fasting plasma glucose level, hypoglycaemic episodes, morbidity, adverse effects and costs.
Main results: Twelve randomised controlled trials were included and evaluated outcomes in 3259 randomised patients. Intervention duration ranged from 6 months (26 weeks) to 12 months (52 weeks). Nine trials compared SMBG with usual care without monitoring, one study compared SMBG with SMUG, one study was a three-armed trial comparing SMBG and SMUG with usual care and one study was a three-armed trial comparing less intensive SMBG and more intensive SMBG with a control group. Seven out of 11 studies had a low risk of bias for most indicators. Meta-analysis of studies including patients with a diabetes duration of one year or more showed a statistically significant SMBG induced decrease in HbA(1c) at up to six months follow-up (-0.3; 95% confidence interval (CI) -0.4 to -0.1; 2324 participants, nine trials), yet an overall statistically non-significant SMBG induced decrease was seen at 12 month follow-up (-0.1; 95% CI -0.3 to 0.04; 493 participants, two trials). Qualitative analysis of the effect of SMBG on well-being and quality of life showed no effect on patient satisfaction, general well-being or general health-related quality of life. Two trials reported costs of self-monitoring: One trial compared the costs of self-monitoring of blood glucose with self-monitoring of urine glucose based on nine measurements per week and with the prices in US dollars for self-monitoring in 1990. Authors concluded that total costs in the first year of self-monitoring of blood glucose, with the purchase of a reflectance meter were 12 times more expensive than self-monitoring of urine glucose ($481 or 361 EURO [11/2011 conversion] versus $40 or 30 EURO [11/2011 conversion]). Another trial reported a full economical evaluation of the costs and effects of self-monitoring. At the end of the trial, costs for the intervention were £89 (104 EURO [11/2011 conversion]) for standardized usual care (control group), £181 (212 EURO [11/2011 conversion]) for the less intensive self-monitoring group and £173 (203 EURO [11/2011 conversion]) for the more intensive self-monitoring group. Higher losses to follow-up in the more intensive self-monitoring group were responsible for the difference in costs, compared to the less intensive self-monitoring group.There were few data on the effects on other outcomes and these effects were not statistically significant. None of the studies reported data on morbidity.
Authors' conclusions: From this review, we conclude that when diabetes duration is over one year, the overall effect of self-monitoring of blood glucose on glycaemic control in patients with type 2 diabetes who are not using insulin is small up to six months after initiation and subsides after 12 months. Furthermore, based on a best-evidence synthesis, there is no evidence that SMBG affects patient satisfaction, general well-being or general health-related quality of life. More research is needed to explore the psychological impact of SMBG and its impact on diabetes specific quality of life and well-being, as well as the impact of SMBG on hypoglycaemia and diabetic complications.