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Iron deficiency anemia

Background

Overview

Definition
IDA is a form of anemia that results from inadequate iron supply for erythropoiesis, and is defined as a hemoglobin two SDs below normal with evidence of low body iron stores.
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Pathophysiology
IDA can be caused by increased iron demand (pregnancy, infancy), insufficient iron intake, decreased iron absorption (IBD, gastrectomy), chronic blood loss (menorrhagia, systemic bleeding, hookworm infection), drugs (NSAIDs, corticosteroids), genetics (iron-refractory IDA), and iron-restricted erythropoiesis (CKD).
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Epidemiology
In the US, the prevalence of iron deficiency ranges from 4.5-18.0%., while the prevalence of IDA is estimated at 2.9%.
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Disease course
IDA typically presents with hypochromic, microcytic erythrocytes. Clinical manifestations are related to the severity of the anemia, and may additionally include restless leg syndrome, decreased QoL, and increased maternal and newborn mortality.
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Prognosis and risk of recurrence
Iron deficiency is an independent predictor of cardiovascular events in patients with coronary artery disease. Iron deficiency is a risk factor for all-cause mortality in patients with CKD. IDA is also associated with morbidity and mortality in pregnant women.
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Guidelines

Key sources

The following summarized guidelines for the evaluation and management of iron deficiency anemia are prepared by our editorial team based on guidelines from the American Academy of Family Physicians (AAFP 2024,2013), the American Gastroenterological Association (AGA 2024,2020), the British Society for Haematology (BSH 2024), the Society of Cardiovascular Computed Tomography (SCCT/SVM/SCMR/SCA/AHA/ASNC/HRS/ACC/ACS 2024), the U.S. Preventive Services Task Force (USPSTF 2024,2015), ...
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Screening and diagnosis

Etiology: as per BSG 2021 guidelines, recognize that IDA is common following resection or bypass surgery involving the stomach and/or small bowel, including bariatric surgery.
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  • Indications for screening (children)

  • Indications for screening (pregnancy)

  • Diagnostic criteria

Classification and risk stratification

Cancer risk assessment: as per BSG 2021 guidelines, use age, sex, hemoglobin concentration and mean cell volume as independent predictors of risk of gastrointestinal cancer in patients with IDA, as part of a holistic risk assessment.
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Diagnostic investigations

General principles: as per BSG 2011 guidelines, evaluate all levels of anemia in the presence of iron deficiency.
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  • History and physical examination

  • CBC

  • Hemoglobin electrophoresis

  • Iron studies

  • Urinalysis and microscopy

  • Fecal immunochemical testing

  • Screening for celiac disease

  • Screening for H. pylori infection

  • Upper and lower gastrointestinal investigations

  • Small bowel investigations

Diagnostic procedures

Gastric biopsy: as per AGA 2020 guidelines, do not perform a routine gastric biopsy to diagnose atrophic gastritis in patients with IDA.
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  • Small bowel biopsy

Medical management

Iron supplementation, initiation: as per BSG 2021 guidelines, do not defer iron replacement therapy while awaiting investigations for IDA unless colonoscopy is imminent.
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  • Iron supplementation (choice of formulation)

  • H. pylori eradication

Therapeutic procedures

RBC transfusion: as per BSG 2021 guidelines, consider administering limited transfusion of packed red cells in patients with symptomatic IDA. Continue iron replacement therapy after transfusion.
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Specific circumstances

Pregnant patients, prevention: as per USPSTF 2024 guidelines, insufficient to assess the balance of benefits and harms of routine supplementation for iron deficiency and IDA in pregnant females to prevent adverse maternal and infant health outcomes.
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  • Pregnant patients (screening)

  • Pregnant patients (diagnosis)

  • Pregnant patients (iron supplementation)

  • Pediatric patients

  • Young patients (female)

  • Young patients (male)

  • Patients with comorbidities

  • Patients with IBD (screening)

  • Patients with IBD (diagnosis)

  • Patients with IBD (evaluation)

  • Patients with IBD (iron supplementation)

  • Patients with IBD (RBC transfusion)

  • Patients with IBD (monitoring for recurrence)

  • Patients with IBD (management of recurrence)

  • Patients with celiac disease

  • Patients with portal hypertension

  • Patients with gastric antral vascular ectasia

  • Patients with small bowel angioectasia

  • Patients undergoing surgery (assessment and timing of surgery)

  • Patients undergoing surgery (thresholds)

  • Patients undergoing surgery (iron supplements and EPO-stimulating agents)

  • Patients undergoing surgery (RBC transfusion)

Follow-up and surveillance

Follow-up
As per BSG 2021 guidelines:
Monitor patients in the first 4 weeks for hemoglobin response to oral iron and continue treatment for a period of around 3 months after normalization of hemoglobin level to ensure adequate repletion of the marrow iron stores.
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Consider obtaining periodic blood count monitoring in non-anemic patients with iron deficiency.
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  • Management of recurrent disease

Quality improvement

Care pathways: as per BSG 2021 guidelines, all service providers should have clear points of referral and management pathways in patients with IDA.
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