It is now clear that hyperglycaemia of even short duration can be associated with adverse outcome in the acutely ill. Thus, the hyperglycaemic state has been associated with increased mortality in patients undergoing cardiothoracic surgery or suffering acute myocardial infarction, in victims of major trauma and those sustaining brain injury, and in association with community acquired pneumonia.^1–5 In this issue of Thorax Baker and colleagues extend this list, having performed a retrospective analysis of outcome in patients admitted to hospital with an acute exacerbation of chronic obstructive pulmonary disease (COPD).⁶ Multivariate analysis revealed that hyperglycaemia held more adverse prognostic significance even than spirometry. Not surprisingly, the authors propound the hypothesis that rigorous glycaemic control should improve mortality and/or reduce the length of hospital stay in this patient population which is so commonly encountered during the acute general medical take. To this end, they propose that a randomised trial of insulin therapy should be undertaken.

How robust are the data presented in this potentially important study? Although the authors are commendably open about the limitations of their study, these may be significant. Firstly, their (retrospective) identification of patients relied entirely on clinical coding, audits of which have suggested levels of accuracy as low as 60%.⁷ It is therefore unlikely that the study population was both complete and homogeneous. Indeed, the microbiological data presented suggest that a degree …