Editor—We have three comments about Pickup et al's meta-analysis comparing insulin infusion with injection, which may cast a different light on their main conclusion.1
Firstly, the results of the largest study in the meta-analysis, the so called Dusseldorf study, needs careful interpretation. The authors have estimated this study to show a positive result for continuous subcutaneous insulin infusion, with an advantage in percentage of glycated haemoglobin of 0.68%. This figure will be an estimation made from a graph, as exact data are not given in the original paper. This seems to be a correct interpretation of the six month data of this study, but the total duration of the study was two years. At 12, 18, and 24 months the “advantage” of continuous subcutaneous insulin infusion can be estimated to be 0.35%, -0.1%, and -0.2%, respectively. Thus another interpretation of this one study, representing 918 months of the meta-analysis's total of 2522 patient months of pump treatment, will have a substantial impact on the overall outcome of the meta-analysis.
Secondly, the authors did not include the study of Reeves et al in their analysis. This study, albeit small, did not show a difference in glycated haemoglobin between intensified injection therapy and insulin pump therapy.2
Thirdly, modified rapid acting insulins have recently been shown to be advantageous with respect to glycated haemoglobin.3,4 The most relevant comparison is therefore between continuous subcutaneous insulin infusion and multiple injection therapy, both using rapid acting insulin analogues.
Only two such studies have been published. The first, by Hanaire-Broutin et al and included in the meta-analysis, found a 0.35% lower glycated haemoglobin with insulin pump therapy than with injection therapy in 41 patients using a crossover design. However, patients had been receiving insulin pump therapy with human regular insulin for a mean of 5.5 years before entering the trial, which limits the external validity of this study. The second study, by Tsui et al, was published too recently to be included in the meta-analysis but did not show a difference in glycated haemoglobin over nine months in 21 patients.5
We consider that the case for insulin pump treatment in type 1 diabetes has still to be decided. Two large multicentre trials comparing this treatment with optimised injection schemes with rapid acting analogues have been recently completed and should provide clinically useful information.
References
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