The predictive value of plasma neutrophil gelatinase-associated lipocalin on cardiovascular death and all-cause mortality might be mediated by leukocytosis

摘要

We read with interest the paper by Daniels et al. (1), who concluded that higher levels of plasma neutrophil gelatinase-associated lipocalin (NGAL) are associated independently with an increased risk of cardiovascular death and all-cause mortality in a cohort of older community-dwelling adults. The lack of correlation with renal function led the authors to conclude that plasma NGAL provides prognostic information that is independent of glomerular filtration rate, and the modest correlation with C reactive protein also underlines that NGAL would reflect a pathophysiological process distinct from inflammation. We (2), as well as others (3), have shown independently that serum, but not urinary, NGAL levels are influenced dramatically by leukocytosis, especially by a high neutrophil count. The paper by Daniels et al. (1) lacks data regarding leukocyte or neutrophil counts, and therefore, it cannot be excluded that the significant role of plasma NGAL in predicting mortality and cardiovascular outcomes observed in this study might have been mediated largely by these untested parameters, because leukocytosis is per se a significant predictor of noninfective mortality and morbidity, particularly resulting from cardiovascular or cerebrovascular causes (4), thereby biasing their results.