Previous studies have suggested that the EPO response in AUE is inappropriately low however methodological limitations did not allow for definitive conclusions.[19] In the present study linear regression analysis showed that EPO levels in the CKD, ACD and AUE groups were lower by 48%, 46% and 27%, respectively, compared to IDA patients even after adjusting for hemoglobin, eGFR and comorbidities. This evidence concerns the gene EPO and chronic kidney disease.