A 3-Marker Index Improves the Identification of Iron Disorders in CKD Anaemia

Abstract

BACKGROUND Iron disorders are common and complex in chronic kidney disease (CKD). We sought to determine whether a 3-marker index would improve the classification of iron disorders in CKD anaemia. METHODS We studied the association between Hb level and iron indexes combining 2 or 3 of the following markers: serum ferritin (<40 ng/mL), transferrin saturation (TSAT<20%) and total iron binding capacity (TIBC<50 µmol/L) in 1011 outpatients with non-dialysis CKD participating in the Nephrotest study. All had glomerular filtration rates measured (mGFR) by (51)Cr-EDTA renal clearance; 199 also had hepcidin measures. RESULTS The TSAT-TIBC-ferritin index explained Hb variation better than indexes combining TSAT-TIBC or ferritin-TSAT. It showed hypotransferrinaemia and non-inflammatory functional iron deficiency (ID) to be more common than either absolute or inflammatory ID: 20%, 19%, 6%, and 2%, respectively. Hb was lower in all abnormal, compared with normal, iron profiles, and decreased more when mGFR was below 30 mL/min/1.73 m(2) (interaction p<0.0001). In patients with mGFR<30 mL/min/1.73 m(2), the Hb decreases associated with hypotransferrinaemia, non-inflammatory functional ID, and absolute ID were 0.83±0.16 g/dL, 0.51±0.18 and 0.89±0.29, respectively. Compared with normal iron profiles, hepcidin was severely depressed in absolute ID but higher in hypotransferrinaemia. CONCLUSIONS The combined TSAT-TIBC-ferritin index identifies hypotransferrinaemia and non-inflammatory functional ID as the major mechanisms of iron disorders in CKD anaemia. Both disorders were associated with a greater decrease in Hb when mGFR was <30 mL/min/1.73 m(2). Taking these iron profiles into account may be useful in stratifying patients in clinical trials of CKD anaemia and might improve the management of iron therapy.

DOI: 10.1371/journal.pone.0084144

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@inproceedings{Mercadal2014A3I, title={A 3-Marker Index Improves the Identification of Iron Disorders in CKD Anaemia}, author={Lucile Mercadal and Marie H{\'e}l{\`e}ne Metzger and Jean Philippe Haymann and Eric Thervet and J F Boffa and Martin Flamant and François Vrtovsnik and C{\'e}dric Gauci and Marc C Froissart and B{\'e}n{\'e}dicte Stengel}, booktitle={PloS one}, year={2014} }