How to diagnose and manage iron deficiency anemia?

From the Guidelines

Iron deficiency anemia should be diagnosed and managed through a combination of clinical assessment, laboratory testing, and treatment of the underlying cause, with oral iron supplementation as the first-line treatment, according to the most recent guidelines from the British Society of Gastroenterology 1.

Diagnosis

The diagnosis of iron deficiency anemia involves:

• A complete blood count showing low hemoglobin (typically <13 g/dL in men, <12 g/dL in women)
• Low mean corpuscular volume
• Blood smear revealing microcytic, hypochromic red cells
• Confirmatory tests include low serum ferritin (<30 ng/mL), low transferrin saturation (<16%), elevated total iron-binding capacity, and increased soluble transferrin receptor levels
• Serum ferritin is the single most useful marker of iron deficiency anemia, but other blood tests can be helpful if a false-normal ferritin is suspected 1

Management

Management begins with identifying and treating the underlying cause, commonly:

• Blood loss (menstrual, gastrointestinal)
• Poor dietary intake
• Malabsorption
• Oral iron supplementation is the first-line treatment, typically ferrous sulfate 325 mg (containing 65 mg elemental iron) taken 1-3 times daily between meals with vitamin C to enhance absorption
• Side effects include gastrointestinal distress, constipation, and black stools
• If oral therapy fails or isn't tolerated, intravenous iron formulations like iron sucrose (100-200 mg per dose) or ferric carboxymaltose (up to 1000 mg per dose) can be administered
• Response to therapy should be monitored with hemoglobin checks after 2-4 weeks, with expected increases of 1-2 g/dL per month
• Treatment should continue for 3-6 months after hemoglobin normalizes to replenish iron stores
• Dietary counseling to increase iron-rich foods (red meat, leafy greens, legumes) should complement pharmacological treatment
• In patients with inflammatory bowel disease, intravenous iron may be more effective and better tolerated than oral iron, and should be considered as first-line treatment in certain situations 1

Special Considerations

• In the presence of inflammation, a serum ferritin up to 100 mg/L may still be consistent with iron deficiency 1
• The diagnostic criteria for anemia of chronic disease are a serum ferritin >100 mg/L and transferrin saturation <20% 1
• Wireless capsule endoscopy plays an important role in assessment of the small bowel in recurrent or refractory iron deficiency anemia 1

From the Research

Diagnosis of Iron Deficiency Anemia

To diagnose iron deficiency anemia, the following steps can be taken:

• Measure hemoglobin concentration, hematocrit, mean cellular volume, mean cellular haemoglobin, percentage of hypochromic erythrocytes, and serum ferritin levels 2
• Exclude acute phase reaction by history and measurement of C-reactive protein to avoid false negative results 2
• Use an algorithm to lead through the diagnostic process and decision making for possible treatment 2
• Consider the patient's age and sex when interpreting ferritin levels, with cut-offs of 30 µg/l for healthy males and females aged >15 years, 15 µg/l for children from 6-12 years, and 20 µg/l for younger adolescents from 12-15 years 2

Evaluation of Iron Deficiency

Evaluation of iron deficiency status should include:

• Total complete blood count (CBC) test accompanied by other tests of iron status, such as serum iron and ferritin, to pinpoint true iron deficiency 3
• Measurement of serum ferritin as the first laboratory test in the evaluation of microcytosis, with low ferritin levels suggesting iron deficiency 4
• Consideration of underlying sources for iron deficiency, such as blood loss, and investigation of possible gastrointestinal malignancy 4

Management of Iron Deficiency Anemia

Management of iron deficiency anemia includes:

• Counselling and oral iron therapy as a first step in treatment, with preparations containing reasonable but not excessive elemental iron content (28-50 mg) to minimize gastrointestinal side effects 2
• Integration of haem and free iron into the diet, and identification of enhancers and inhibitors of iron uptake 2
• Intravenous iron injection in exceptional cases, such as concomitant disease needing urgent treatment or repeated failure of first-step therapy 2, 5, 6
• Monitoring of treatment success through repeat blood tests after 8 to 10 weeks, and long-term follow-up with regular blood tests to monitor iron stores 2, 5