Simple, widely available lab tests could represent useful markers and predictors of outcome in ICU patients, especially when a strong rationale supports their potential prognostic value. For instance, eosinophil count is tightly and readily regulated by cytokines and is related to the stimulation of the adrenal axis. Likewise, the presence of eosinopenia has already been reported as a marker of infection. In a large prospective study, Abidi et al. [20] evaluated the prognostic value of serial eosinophil count measured daily from ICU admission until the seventh day of stay in 200 patients. The absolute eosinophil count was lower over the entire ICU stay in nonsurvivors. Eosinopenia (\40 cells/mm 3 ) was found to be an independent predictor of ICU mortality, with an area under the ROC curve of 0.82. These findings highlight the usefulness of the inexpensive and probably underused leukocyte formula in the ICU.