What is the diagnosis and management for a patient with microcytic hypochromic anemia and a high RDW?

Diagnosis and Management of Microcytic Hypochromic Anemia with Elevated RDW

Primary Diagnosis

This patient most likely has iron deficiency anemia, as indicated by the combination of low MCH (26.9), low MCHC (30.2), borderline low-normal MCV (88.8), and markedly elevated RDW-CV (16.2) and RDW-SD (52.7). 1, 2

Diagnostic Reasoning

The laboratory pattern is highly characteristic of iron deficiency:

• The elevated RDW (>14.0%) combined with microcytic indices strongly suggests iron deficiency anemia, with this combination being the most powerful discriminator from other microcytic conditions like thalassemia trait 1, 2
• The hypochromia (low MCH and MCHC) with increased red cell size variation (anisocytosis) reflects the heterogeneous population of red cells at different stages of iron depletion 1
• While the hemoglobin (13.7) appears "normal," this does not exclude iron deficiency, as compensatory mechanisms may maintain hemoglobin despite depleted iron stores 1

Required Confirmatory Testing

Order the following tests immediately to confirm iron deficiency:

• Serum ferritin - the single most powerful confirmatory test, with <12 μg/dL being diagnostic of iron deficiency; if inflammation is present, ferritin up to 100 μg/L may still indicate iron deficiency 1, 2
• Transferrin saturation - <30% supports iron deficiency 1
• C-reactive protein (CRP) - to assess for inflammation that may elevate ferritin 2
• Serum iron (low in iron deficiency) and total iron binding capacity (increased in iron deficiency) 1

Investigation for Underlying Cause

For this patient, the following investigations are mandatory:

• Gastrointestinal evaluation is essential - if the patient is male or post-menopausal female, both upper and lower endoscopy should be performed to exclude malignancy (colonic cancer/polyps, gastric cancer) 1, 2
• Screen for celiac disease with tissue transglutaminase antibodies, as malabsorption is a common cause 1
• Assess for NSAID use, which can cause occult GI bleeding 1
• In pre-menopausal women, menstrual blood loss is the most common cause 1
• Evaluate dietary iron intake 1

Treatment Protocol

Initiate oral iron supplementation as first-line therapy:

• Start oral iron (ferrous sulfate 325 mg daily or equivalent) 1, 2
• A therapeutic response after three weeks of oral iron confirms the diagnosis of iron deficiency 1
• Continue iron therapy for 3-6 months after hemoglobin normalization to replenish iron stores 1

Alternative approaches if oral iron fails:

• If no response after 4 weeks, reassess diagnosis and adherence 1
• For malabsorption, intolerance to oral iron, or inflammatory bowel disease, intravenous iron may be necessary 1

Monitoring Strategy

• Monitor hemoglobin, MCV, and RDW at 4 weeks to assess treatment response 1
• Serial RDW monitoring is valuable for assessing response to therapy 2
• Expect reticulocytosis within 1-2 weeks and hemoglobin rise within 4 weeks of adequate iron replacement

Critical Pitfalls to Avoid

• Do not assume thalassemia trait based solely on ethnicity without laboratory confirmation - the elevated RDW makes thalassemia trait unlikely, as thalassemia typically has normal or only mildly elevated RDW 2, 3
• Do not overlook combined deficiencies (iron plus B12 or folate), which may mask typical findings and result in normal MCV despite abnormal RDW 1, 2
• Do not fail to investigate for GI malignancy in adult men and post-menopausal women with confirmed iron deficiency 2
• Anemia of chronic disease can coexist with iron deficiency and may complicate interpretation 1