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Iron deficiency anemia

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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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 European Society of Gastrointestinal Endoscopy (ESGE 2023), the British Society of Gastroenterology (BSG 2021; 2011), the American College of Obstetricians and Gynecologists (ACOG 2021), the American Gastroenterological Association (AGA 2020), the U.S. Preventive Services Task Force (USPSTF 2015), the Royal College of Obstetricians and Gynaecologists (RCOG 2015), the European Crohn's and Colitis Organisation (ECCO 2015), and the American Academy of Family Physicians (AAFP 2013).
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Guidelines

1.Screening and diagnosis

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

  • Indications for screening (pregnancy)

  • Diagnostic criteria

2.Classification and risk stratification

Cancer risk assessment: 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.
A

3.Diagnostic investigations

General principles: evaluate all levels of anemia in the presence of iron deficiency.
B

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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

4.Diagnostic procedures

Gastric biopsy: do not perform a routine gastric biopsy to diagnose atrophic gastritis in patients with IDA.
D

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  • Small bowel biopsy

5.Medical management

Iron supplementation: as per BSG 2021 guidelines, do not defer iron replacement therapy while awaiting investigations for IDA unless colonoscopy is imminent.
D
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  • H. pylori eradication

6.Therapeutic procedures

Red blood cell transfusion
Consider administering limited transfusion of packed red cells in patients with symptomatic IDA. Continue iron replacement therapy after transfusion.
B
Consider administering limited transfusion of packed red cells in patients with symptomatic IDA. Continue iron replacement therapy after transfusion.
B

7.Specific circumstances

Pregnant patients, screening, RCOG: obtain screening for anemia in pregnant patients at 28 weeks of gestation. Obtain an additional CBC at 20-24 weeks in patients with multiple pregnancies.
B

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  • Pregnant patients (diagnosis)

  • Pregnant patients (prevention)

  • Pregnant patients (iron supplementation)

  • Young patients (female)

  • Young patients (male)

  • 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 of recurrence)

  • Patients with IBD (management of recurrence)

  • Patients with comorbidities

8.Follow-up and surveillance

Follow-up
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.
B
Consider obtaining periodic blood count monitoring in non-anemic patients with iron deficiency.
C

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  • Management of recurrent disease

9.Quality improvement

Care pathways: all service providers should have clear points of referral and management pathways in patients with IDA.
B
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