Oct 10, 2012 Do insulin pumps and continuous glucose monitors actually improve outcomes?
Nearly every day in my practice, a patient with diabetes asks me whether he or she should switch from multiple daily insulin injections to an insulin pump. I often have a discussion with patients about whether or not they should be using a CGM (continuous glucose monitor) to help monitor blood glucose instead of just using SMBG (self-monitoring of blood glucose). As an endocrinologist, it is very important to be able to advise patients about specifically what these new technologies have to offer them. Do they decrease mortality? Do they decrease long-term diabetes complications? Do they improve glycemic control? Do they improve quality of life for patients? Do they lower costs? All new medical technologies need to undergo a rigorous evaluation and testing with these types of questions in mind. This is critical not just so that I can be honest and helpful to my patients, but also from the overall perspective of the healthcare system.
In that vein, Yeh et al recently published a meta-analysis in the Annals of Internal Medicine called “Comparative Effectiveness and Safety of Methods of Insulin Delivery and Glucose Monitoring for Diabetes Mellitus: A Systematic Review and Meta-analysis.”
This meta-analysis, funded by AHRQ, looked at the differences between:
- MDI vs CSII (multiple daily injections vs continuous subcutaneous insulin infusion)
- Type 1 vs type 2 diabetes
- SMBG (self-monitoring of blood glucose) vs rt-CGM (real-time continuous glucose monitoring)
What types of studies did they include in their meta-analysis?
- Studies of adults, adolescents, or children with type 1 or type 2 diabetes mellitus
- Studies from 1966-2012
- 19 studies comparing CSII with MDI (>3 injections per day of either basal/bolus insulin or NPH/regular)
- 10 studies comparing CGM with SMBG (>3 fingersticks per day)
- 4 studies comparing SAP (Sensor-augmented pump) use with MDI + SMBG
* Studies were excluded if regular insulin was used in the CSII (pump) group (they felt this to be a weakness of prior analyses)
Here is the key data table:
A few things pop out from this table:
- Overall, they assessed the strength of evidence as relatively weak.
- In children and adolescents, CSII showed no difference in clinical outcomes from MDI. CSII was better in terms of quality-of-life.
- In adults with type 1 diabetes, CSII led to more symptomatic hypoglycemia, but better hemoglobin A1c and quality-of-life.
- There were no differences between CSII and MDI in adults with type 2 diabetes.
- CGM, whether with an insulin pump or not, led to a benefit in glycemic control without any difference in hypoglycemia.
Some concerns and words of caution when interpreting these results:
- Meta analyses can always suffer from publication bias. That is, studies are much more likely to be published if they show positive results. So it is possible that studies have been done that generated results that would have shown no difference between the two methods being studied, but these may never have been published and thus cannot be included in the meta-analysis.
- These studies all had durations of 12-52 weeks. There were no studies reporting on long-term outcomes like micro or macrovascular disease.
- 24 of the articles (approximately 2/3) were supported by pharmaceutical companies
What does this mean?
According to this meta-analysis, CGMs did improve glycemic control. Insulin pumps did not appear to have a significant effect on clinical outcomes, but did positively effect quality of life. Remember that the studies included were all between 12 and 52 weeks, so one major limitation is that any longer-term effects would not be teased out.
While some may discount the quality of life improvements seen with the pump as being less important than clinical outcomes, I caution people from doing so. In a condition as omnipresent as diabetes, maintaining good quality of life for the patient is critical and a very important goal.
In the end, the decision about whether or not to use one of these devices comes down to a conversation with the patient and their family, based on their personal preferences and what each device might offer them in terms of benefits and harms. This meta-analysis adds some more information to that conversation.
Finally, this meta-analysis shows that we simply need more data to study so that more concrete conclusions can be drawn.