Objectives: To assess the clinical and cost-effectiveness of continuous subcutaneous insulin infusion (CSII) compared with multiple daily injections (MDI) in the delivery of intensive insulin therapy for the treatment of diabetes mellitus.
Data sources: Electronic databases, references of retrieved articles and manufacturer submissions. Experts in the field were consulted.
Review methods: For the systematic review of clinical and cost-effectiveness, studies were assessed for inclusion according to predefined criteria by two reviewers. Data extraction and quality assessment were undertaken by one reviewer and checked by a second reviewer. Data on clinical effectiveness were synthesised through a narrative review with full tabulation of all eligible studies, with meta-analysis performed where appropriate.
Results: Twenty studies comparing CSII with MDI were identified. Quality was generally poor. In adults with Type 1 diabetes, glycated haemoglobin improved by 0.61% (95% CI -1.29 to 0.07) in longer term studies, although this improvement was smaller when a study using bovine ultralente was excluded. A reduction in insulin dose with CSII of about 12 units per day (-11.90, 95% CI -18.16 to 5.63) was found in short-term studies, with smaller differences in longer term studies. Body weight and cholesterol levels were similar between treatments. Hypoglycaemic events did not differ significantly between CSII and MDI in most trials, but some found fewer events with CSII and one found more hypoglycaemia and hypoglycaemic coma with CSII. There was no consistency between the studies in patient preference, but progress has been made both with insulin pumps and injector pens since the publication of many of the older studies. No difference in glycated haemoglobin between CSII and MDI was found in pregnancy; one study found less insulin was required by patients with CSII, but two other studies found no significant difference. One study of adolescents found lower glycated haemoglobin and insulin dose with CSII whereas a second study found no significant difference. In CSII analogue insulin was associated with lower glycated haemoglobin levels than soluble insulin. No economic evaluations comparing CSII with MDI were identified. The estimated additional cost of CSII compared to MDI varies from GBP1091 per annum to GBP1680 per annum, according to the make of the insulin pump and the estimated life of the device. These estimates include the costs for the insulin pump, the consumables associated with delivery of CSII, and an allowance for the initial education required when patients switch from MDI to CSII. The largest component of the annual cost for CSII is the cost of consumable items (e.g. infusion sets).
Conclusions: When compared with optimised MDI, CSII results in a modest but worthwhile improvement in glycated haemoglobin in adults with Type 1 diabetes. It has not been possible to establish the longer term benefits of such a difference in glycated haemoglobin, although there is an expectation that it would be reflected in a reduction in long-term complications. More immediate primary benefits from CSII may be associated with an impact on the incidence of hypoglycaemic events and the dawn phenomenon, and greater flexibility of lifestyle. However, there is limited evidence on this, and information presented to offer context on quality-of-life is based on testimonies from those patients who have had a positive experience of CSII. The estimated cost to the NHS per year for CSII would be around GBP3.5 million in England and Wales if 1% of people with Type 1 diabetes used CSII, GBP10.5 million for 3%, and GBP17.5 million for 5%. Further research should focus on wider benefits of CSII, such as flexibility of lifestyle and quality of life, and on the psychological impact of wearing a device for 24 hours every day. Research into the use of CSII in children of different ages is also needed.