Management of Microcytic Anemia

Diagnostic Approach

The American College of Physicians recommends serum ferritin as the most specific test for iron deficiency, with levels <15 μg/L indicating absent iron stores and <30 μg/L indicating low body iron stores 1
A ferritin cut-off of 45 μg/L provides optimal sensitivity and specificity for iron deficiency in clinical practice, according to the American Academy of Family Physicians 1
Transferrin saturation (TSAT) should be evaluated as it is more sensitive for detecting iron deficiency than hemoglobin concentration alone, as suggested by the American Society of Hematology 1
A low MCV with RDW >14.0% suggests iron deficiency anemia, while a low MCV with RDW ≤14.0% suggests thalassemia minor, based on guidelines from the College of American Pathologists 1
In patients with unexplained microcytic anemia with increased TSAT, genetic disorders such as SLC11A2 defects should be considered, as recommended by the National Institute of Health 2
For patients with unexplained hypochromic microcytic anemia with low iron binding capacity and increased ferritin, hypotransferrinemia should be considered, according to the European Hematology Association 3, 4

The American College of Cardiology recommends first-line treatment with oral iron supplementation with ferrous sulfate 200 mg three times daily for at least three months after correction of anemia 1
Alternative formulations include ferrous gluconate and ferrous fumarate if ferrous sulfate is not tolerated, as suggested by the American Gastroenterological Association 1
Adding ascorbic acid can enhance iron absorption, based on guidelines from the National Institutes of Health 1
A good response to iron therapy is defined as a hemoglobin rise ≥10 g/L within a 2-week timeframe, which confirms iron deficiency, according to the American Society of Clinical Oncology 1
For patients who fail to respond to oral iron therapy, consider intravenous (IV) iron if there is malabsorption, as recommended by the European Society for Medical Oncology 1

The American Academy of Pediatrics recommends monitoring hemoglobin concentration and red cell indices at three-monthly intervals for one year and then after a further year 1
Provide additional oral iron if hemoglobin or MCV falls below normal, as suggested by the American College of Physicians 1
For patients receiving iron therapy, monitor for iron overload, particularly in genetic disorders, according to the National Institute of Health 5
In cases of SLC11A2 defects, monitor iron status to detect toxic iron loading early; MRI of the liver should be considered since normal serum ferritin does not exclude liver iron loading, as recommended by the European Hematology Association 3, 5

Genetic testing should be considered in patients with refractory microcytic anemia despite adequate iron supplementation, according to the American Society of Human Genetics 6, 2
Family screening may be recommended for patients diagnosed with genetic disorders affecting iron metabolism, as suggested by the National Society of Genetic Counselors 3, 4
In children with severe unexplained microcytic sideroblastic anemia, defects in SLC25A38 should be considered, based on guidelines from the Pediatric Hematology/Oncology Society 5
In male patients presenting with mild microcytic anemia and ataxia, defects in ABCB7 should be considered, as recommended by the European Neurological Society 3
Avoid overlooking combined deficiencies, such as iron deficiency coexisting with B12 or folate deficiency, according to the American College of Physicians 1

In patients with unexplained microcytic anemia despite normal iron studies, consider genetic disorders of iron metabolism or heme synthesis 7

In men and post-menopausal women, iron deficiency anemia is most commonly caused by gastrointestinal blood loss or malabsorption 8
In an 18-year-old, common causes to investigate include menstrual blood loss if female, gastrointestinal blood loss, poor dietary intake, malabsorption, and NSAID use 8
For gastrointestinal blood loss, upper and lower gastrointestinal endoscopy may be necessary depending on risk factors and severity 8