, Volume 52, Issue 10, pp 2234-2235
Date: 07 Aug 2009

The longest ever randomised controlled trial of insulin glargine: study design and HbA1c findings

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To the Editor: I would like to discuss the study design and reporting of the recent study by Rosenstock and colleagues that examined the long-term safety of insulin glargine (A21Gly,B31Arg,B32Arg human insulin) vs neutral protamine Hagedorn (NPH) insulin with respect to progression of retinopathy [1].

It is possible that the inclusion of individuals with type 2 diabetes who, at baseline, had a mean duration of prior exposure to insulin of 5 years, had an average duration of diabetes of almost 11 years, and had not developed anything more than non-proliferative retinopathy may have introduced bias in the form of a ‘survival effect’. That is, these patients could be those least likely to develop more severe visual loss, irrespective of their treatment regimen. This would have reduced the power of the study to detect any change resulting from insulin glargine exposure. There appeared to be considerable treatment heterogeneity in the respective treatment arms. For example, the mean total in