To the Editor.
—In a cohort analyis, Dr Levy and associates1 found that comorbidities alone did not explain the high mortality rate seen in the setting of acute renal failure. They compared 183 patients who developed acute renal failure after intravenous contrast administration with a cohort matched for age, baseline creatinine levels, and type of contrast study. They examined 20 demographic and clinical variables and a number of physiological characteristics and determined that, after adjustment for these factors, the development of acute renal failure was still associated with a significant increase in mortality (odds ratio of 5.5).Unfortunately, we do not know why renal failure developed in the index patients and not in the matched cohort. As a result, a confounding variable could easily have been missed—one or more factors, not measured here, responsible for both the development of renal failure and the excess in mortality. The authors would
Jacobson M. Acute Renal Failure and Mortality. JAMA. 1996;276(7):529. doi:10.1001/jama.1996.03540070025024