Iron Deficiency and Anemia, Inflammatory Bowel Disease (IBD) — Iron Deficiency — Clinical Pathway: Outpatient Specialty Care and Primary Care

Inflammatory Bowel Disease with Iron Deficiency and Anemia Clinical Pathway — All Settings

Iron Deficiency

Anemia is the ultimate consequence of ID. However, iron is essential to the functioning of all organs and providers should recognize ID as a clinical condition distinct from anemia and treat accordingly. ID independent from anemia has been related to decrease physical performance and cognitive function, chronic fatigue, and headache, all of which are responsive to iron replacement therapy.

Diagnosis of Iron Deficiency in IBD

The analysis of iron storage in patients with IBD is complicated by the fact that ferritin is an acute phase protein and can be increased in the setting of chronic inflammation, whereas transferrin is a negative acute phase protein and can be decreased in the inflammatory state. Therefore, given the possibility of ongoing inflammation in IBD, markers of stored iron should be interpreted with reference to the patient's disease activity at the time and optimization of anti‐inflammatory therapy and iron supplementation should go hand in hand.

Iron Storage Indices

  • Serum ferritin is a measure of total body iron stores.
    Ferritin < 30 ug/L reflects iron store depletion.
  • Transferrin saturation (TSAT) measures the iron content of circulating transferrin and its availability for erythropoiesis.
    A TSAT < 20% reflects a reduced availability of iron for erythropoiesis, either due to total iron deficiency or due to functional iron deficiency.

Definition of Iron Deficiency in IBD

  • In the absence of inflammation, serum ferritin level < 30 ug/L indicates absolute lack of iron stores.
  • In patients with active disease, a serum ferritin level < 100 μg/L and TSAT < 20% indicate iron deficiency. A combination of absolute and functional iron deficiency is likely in this scenario and supplementation with iron is indicated.
  • In patients with active disease, a serum ferritin level > 100 ug/L and TSAT < 20% indicate functional iron deficiency. This term refers to the iron sequestration occurring at times of inflammation and mediated by increased hepcidin levels. Although iron store may be adequate, the iron is not readily available for synthesis of new hemoglobin.

Stages of Iron Depletion

Deplete iron stores Iron deficiency without anemia Iron deficiency anemia
  • ↓ Serum ferritin
  • ↓ TSAT
  • ↓ Hemoglobin
  • ↓ MCV

Definitions Used for Assessing Iron Status

Assessment of Iron Store
Iron deficiency in relation to disease activity Inactive IBD Ferritin < 30 ug/L
Active IBD Ferritin < 100 ug/L and TSAT < 20%
Iron overload Serum ferritin > 800 ug/L

Measurement of soluble transferrin receptor (sTfR) level, sTfR/log ferritin index, percentage of hypochromic red cells and reticulocyte hemoglobin content may be considered to determine iron deficiency in state of inflammation. These labs are not available at all laboratories.