Ferritin and transferrin saturation cannot be used to diagnose iron-deficiency anemia in critically ill patients

Abstract

Introduction: Iron-deficiency anemia (IDA) is the most common anemia globally. The frequency of IDA among critically ill patients is not known. The aim of our study was to analyse performance of standard iron metabolism parameters for diagnosis of IDA in the critically ill. Material and methods: We performed a retrospective analysis of consecutive anemic patients admitted to the intensive care unit. We based on various cut-off values for ferritin and/or transferrin saturation (TfS), determined the incidence of IDA. Results: The population consisted of 27 (53%) men and 24 (47%) women. The median hemoglobin concentration was 96 [interquartile range (IQR) 87–109] g/L. The studied population had markedly increased concentrations of C-reactive protein [119 (IQR 44–196) mg/L], and ferritin [686 (385–1,114) µg/L], whereas iron concentration and TfS were below reference values. Depending on the cut-off value chosen IDA could be diagnosed in between 7.8% (ferritin <100 µg/L +TfS <20%) and 56.9% (TfS <20%) of patients. Conclusions: Ferritin and transferrin saturation cannot be used for a precise diagnosis of IDA caused by absolute or functional iron deficiency in the critically ill.