Table 1.

Markers of Fe stores in patients with CKDa

Fe Stores MarkerAdvantagesLimitations
Bone marrow Fe via biopsyGold standardInvasive, painful, semiquantitative
Liver Fe via biopsyGold standardInvasive, risk for complications, semiquantitative
Liver Fe via SQUIDNoninvasive, safeInvestigational; limited experience in CKD
Serum ferritinLow levels are highly specific for Fe deficiencyModerately high levels are mostly due to non–Fe-related conditions
Serum transferrin saturation ratio (ISAT)More reliable than ferritin, higher sensitivity than ferritinDenominator (TIBC) can be low in malnutrition and/or inflammation
Serum FeDirect measurement of circulating FeDiurnal fluctuation, can be low in inflammation
CHrMeasures immediate incorporation of Fe into reticulocytesLimited data in CKD, cutoff level debatable
PHRCSimilar to CHr (see above)Samples cannot be shipped to outside laboratories
sTfRCorrelates with transferrin receptors on erythroblastsMixed results, unknown cutoff levels
ZnPPMay be less confounded by inflammationAffected by non–Fe-related factors such as lead level
HepcidinMay detect the presence of functional Fe deficiencyCurrently no reliable assay for its serum measurement
  • a CHr, reticulocyte hemoglobin content; CKD, chronic kidney disease; Fe, iron; ISAT, iron saturation ratio; PHRC, Percentage of hypochromic red cells; SQUID, superconducting quantum interference device; sTfR, Soluble transferrin receptor; TIBC, total iron binding capacity; ZnPP, erythrocyte zinc protoporphyrin.