First, plasma NGAL—in contrast with urinary NGAL—may not be a particularly appropriate tubular marker; it is strongly related to glomerular filtration rate, as reflected by its correlation with GFR and creatinine, and also involved in iron scavenging and immune response, as indicated by the correlation with markers such as CRP and markers of anemia [27,28]. Here, CRP is linked to anemia (phenotype).