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This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
Patients with type 2 diabetes who monitor their blood glucose themselves may see small, short-term improvements in blood sugar control. This is not enough to be clinically important or outweigh the costs and personal inconvenience of long-term self-testing.
Self-monitoring is a well-established strategy for type 1 diabetes and for people with type 2 who need insulin. The benefit for all people with type 2 is debatable. This review pooled 24 randomised controlled trials comparing self-monitoring with any control strategy for people not taking insulin.
Self-monitoring gave a 0.3 percentage point reduction in glycated haemoglobin (HbA1c) at six months. This is just below the 0.4% threshold for a meaningful clinical difference in this measure of average 3-month sugar control. People who had poorer blood glucose control at the start saw a greater benefit. However, there was no difference between the self-monitoring and control groups by 12 months.
The review supports current guideline recommendations that self-monitoring is not routinely used for people with type 2 diabetes controlled on diet or tablets.
Why was this study needed?
There are around 3.7 million people living with diabetes in the UK. Around 90% of those affected have type 2 diabetes.
Management of type 2 diabetes usually begins with lifestyle changes, followed by the addition of oral blood-glucose-lowering medications, progressing to additional drugs and insulin if needed. Blood glucose is monitored by measuring HbA1c every three to six months. The aim is to keep HbA1c ideally below 6.5% or 48mmol/mol.
Self-monitoring of blood glucose is important for patients treated with insulin. A 2012 Cochrane review identified 12 trials assessing benefit for people with type 2 diabetes who are not taking insulin. It found that monitoring gave only small improvements in blood glucose that were not maintained beyond six months.
This review took another look at the topic to establish whether there is now enough evidence to revise clinical practice.
What did this study do?
This systematic review identified 24 recent randomised controlled trials involving 5,454 people with type 2 diabetes. Average HbA1c at baseline was 8.1% (65-66mmol/mol).
The majority of trials compared self-monitoring of blood glucose with no intervention, two compared with urine glucose monitoring and two compared with once-weekly monitoring. Twelve studies took ≥seven glucose measures per week, others took daily measures, and some took multiple daily measures on a few days per week.
The reviewers excluded trials of continuous self-monitoring; where monitoring was part of a more complex intervention (such as education); and where patients were taking several daily insulin injections (basal bolus). Four studies included people on less intensive insulin.
The evidence was judged as low to moderate quality, mainly because participants and assessors were aware of the treatment they were allocated to and study results were variable.
What did it find?
- At three months, HbA1c was 0.31% lower (95% confidence interval [CI]: -0.57 to -0.05) in the self-monitoring compared with the control group. This is just below the 0.4% threshold considered to be a meaningful clinical difference. The meta-analysis included 11 studies (2,558 patients) with highly variable results giving less confidence in the pooled estimate.
- A similar difference was maintained at six months: HbA1c 0.34% lower (95% CI -0.52 to -0.17) in the self-monitoring group. This meta-analysis included 19 studies (4,338 patients), again with mixed results.
- After 12 months, there was no difference between the self-monitoring and control groups (HbA1c -0.10%; 95% CI -0.28 to +0.08), based on 10 studies (2,427 patients).
- Patients whose HbA1c was higher than 8% at baseline benefited more from self-monitoring. They showed 0.83% greater reduction in HbAc1 at three months (95% CI -1.55 to -0.11; four studies) and -0.48% at six months (95% CI -0.77 to -0.19; 11 studies). However, they too showed no benefit after 12 months (0.01%; 95% CI -0.10 to +0.12; four studies).
What does current guidance say on this issue?
The 2015 NICE guideline on management of type 2 diabetes recommends that self-monitoring should not be routinely offered unless the person:
- is taking insulin,
- has low blood glucose (hypoglycaemia),
- is taking oral medication that may increase their risk of hypoglycaemia while driving or operating machinery,
- is pregnant or planning to become pregnant.
Doctors may consider offering self-monitoring of blood glucose in the short-term for people starting treatment with steroids or to confirm suspected hypoglycaemia.
What are the implications?
This study finds an additional 12 trials compared with a 2012 Cochrane review and arrives at broadly the same conclusion. For people with type 2 diabetes who are not using insulin, any benefit from self-monitoring is small and doesn’t last beyond six months.
There are some limitations to the evidence in terms of the diversity of the trials, patient groups and monitoring regimens. But overall it supports guideline recommendations that self-monitoring is not used routinely for people with type 2 diabetes unless there is a specific reason to do so.
Citation and Funding
Machry RV, Rados DV, Gregório GR, Rodrigues TC. Self-monitoring blood glucose improves glycemic control in type 2 diabetes without intensive treatment: A systematic review and meta-analysis. Diabetes Res Clin Pract. 2018;142:173-87.
Funded by Fundo de Incentivo a Pesquisa do Hospital de Clinicas de Porto Alegre, Brazil.
Bibliography
Diabetes UK. Diabetes prevalence 2017. London: Diabetes UK; 2017.
NICE. Type 2 diabetes in adults: management. NG28. London: National Institute for Health and Care Excellence; 2015.
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