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February 4, 2004

Exogenous Insulin and Hypoglycemia as Prognostic Factors in Critically Ill Patients

Author Affiliations

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2004;291(5):558. doi:10.1001/jama.291.5.558-b

To the Editor: We agree with Dr Finney and colleagues1 that current evidence suggests that higher levels of exogenous insulin do not, in themselves, reduce mortality. However, their conclusion that glucose regulation to levels below 145 mg/dL (8.0 mmol/L) was responsible for the beneficial effect reported was too strong.

In the authors' regression analysis, glucose regulation was stratified as tertiles of time spent in 6 predefined glucose bands. When compared with patients whose majority of glucose levels were above the upper limit of the 111- to 144-mg/dL (6.1-8.0 mmol/L) band, patients in and below this band were more likely to survive. Glucose level, however, is actually a continuous variable. Stratification may entail a loss of information that inflates P values and also may arbitrarily group patients together. By contrast, the authors could have used their data to discover the exact threshold level in a certain population, perhaps by calculating the coefficient of variance of the mean glucose level or a time-averaged glucose level.

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