Continuous subcutaneous insulin infusion (CSII) versus multiple insulin injections for type 1 diabetes mellitus

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Type 1 diabetes arises from a failure of insulin secretion, which leads to elevated blood glucose and disturbances in carbohydrate, fat and protein metabolism. There is no means of either preventing or curing type 1 diabetes. Instead, life-long insulin replacement and monitoring of blood glucose levels are required. The conventional means for taking insulin has for some time involved several injections each day, usually two, three or four. However, continuous subcutaneous insulin infusion provides an alternative. Our Cochrane review compares multiple injections with continuous subcutaneous insulin infusion (1). Continuous subcutaneous insulin infusion, or CSII, involves attachment, via a catheter, to an insulin pump. The pump is programmed to deliver insulin to match the person's needs. They can also deliver extra doses themselves to cover meals and correct blood glucose fluctuations. Before starting the review, we knew of numerous studies that had evaluated the two ways of administering insulin but many of these were of poor quality and previous reviews were either out of date or had not used rigorous methodology. This meant that there was uncertainty about which treatment is better. To overcome this, we used a carefully prespecified methodology and searched the literature up to July of 2009. We found and reviewed 23 studies, published from 1982 to 2008. These had recruited a total of 976 patients from a dozen different countries across Europe, North America and the Middle East. Most of the studies had been done in adults, but seven were performed in children. Compared to multiple injections, CSII led to a slight improvement in overall blood glucose control and reduced the frequency of severe hypoglycaemia by at least 50% in most studies. We were not able to investigate short and long term adverse effects, and late complications of diabetes or mortality, because of a lack of data in the trials. While our Cochrane review presents a rigorous and comprehensive analysis of the evidence, there are still many issues that need to be addressed in future trials. Type 1 diabetes may occur at any age and it is one of the most common chronic diseases of childhood and adolescence, so it is interesting that so few patients took part in these trials comparing CSII with multiple injections. Although there is a relatively large number of studies, 23, these tended to be fairly small. The largest recruited 275 patients, but eighteen of the studies had fewer than 50 participants. It is important to be cautious about conclusions drawn from such small trials. Evidence about adverse effects, late complications and mortality is also essential to well informed decision making and needs to be gathered in large scale methodologically rigorous trials. Information about cost effectiveness would also help in making the choice between these two types of insulin therapy.