What is the best course of action for a patient with microcytic anemia, elevated reticulocyte count, normal WBC and differential, and increased platelets?

Microcytic Anemia with Elevated Reticulocytes and Thrombocytosis

This patient requires immediate investigation for gastrointestinal blood loss with bidirectional endoscopy (upper endoscopy and colonoscopy), as the combination of microcytic anemia with elevated reticulocytes indicates active bleeding with compensatory bone marrow response, and the thrombocytosis (reactive thrombocytosis) further supports ongoing blood loss. 1

Interpretation of Laboratory Findings

The laboratory pattern reveals critical diagnostic information:

• Microcytic hypochromic anemia (low MCV, MCH, MCHC) with severely low hemoglobin (8.2 g/dL) indicates iron deficiency as the most likely etiology 1
• Elevated reticulocyte count (1.5% with absolute count 55,050) demonstrates appropriate bone marrow response, which excludes nutritional deficiencies as the sole cause and instead indicates active blood loss or hemolysis 2
• Reactive thrombocytosis (platelets 470) is a common finding in iron deficiency anemia and supports chronic blood loss 1
• Normal WBC and differential excludes bone marrow failure, infiltrative processes, or hematologic malignancy 2

Immediate Diagnostic Workup

Order the following tests immediately:

• Serum ferritin and transferrin saturation (TSAT) to confirm iron deficiency: ferritin <30 μg/L confirms iron deficiency in the absence of inflammation, while TSAT <20% indicates functional iron deficiency 3, 1
• Red cell distribution width (RDW): elevated RDW >14.0% strongly supports iron deficiency anemia rather than thalassemia trait 3, 1
• Haptoglobin, LDH, and indirect bilirubin to exclude hemolysis, though the microcytic pattern makes this less likely 2
• Stool guaiac testing for occult gastrointestinal bleeding 1

Critical Source Investigation

The elevated reticulocyte count with microcytic anemia mandates investigation for the source of blood loss:

• Gastrointestinal blood loss is the most common cause in adults with iron deficiency anemia, and bidirectional endoscopy is required to exclude malignancy 3, 1
• In men or non-menstruating women with confirmed iron deficiency, fast-track gastrointestinal referral is warranted regardless of hemoglobin level 1
• Consider celiac disease screening if malabsorption is suspected 1
• Evaluate for menstrual blood loss in premenopausal women, though the severity here suggests additional sources 1

Treatment Algorithm

Initiate oral iron supplementation immediately while investigating the source:

• Ferrous sulfate 200 mg three times daily for at least 3 months after hemoglobin correction to replenish iron stores 3, 1
• Add ascorbic acid (vitamin C) to enhance iron absorption 3
• Expected response: hemoglobin should rise ≥10 g/L within 2 weeks if iron deficiency is the cause 1
• Switch to intravenous iron (iron sucrose or iron gluconate) if malabsorption is present, patient fails oral therapy, or ongoing losses exceed oral replacement capacity 3, 1

Monitoring and Follow-up

• Recheck hemoglobin and reticulocyte count in 2 weeks to confirm response to iron therapy 1
• Monitor hemoglobin and red cell indices at 3-month intervals for 1 year, then annually 3
• Continue iron supplementation for at least 3 months after hemoglobin normalization to replenish iron stores 1

Common Pitfalls to Avoid

Do not assume this is simple iron deficiency without investigating the source:

• The elevated reticulocyte count indicates active ongoing blood loss, not just chronic depletion 2
• Failure to investigate for gastrointestinal malignancy in adults with iron deficiency anemia is a critical error 3, 1
• Do not delay endoscopy while waiting for iron supplementation response—investigate concurrently 1

Consider alternative diagnoses if iron studies are normal:

• If ferritin is normal/high with low TSAT, consider anemia of chronic disease or mixed picture 2, 1
• If MCV is disproportionately low relative to degree of anemia with normal iron studies, order hemoglobin electrophoresis to exclude thalassemia trait 1
• If patient fails to respond to adequate iron supplementation after 3 months, consider genetic disorders of iron metabolism (IRIDA) or malabsorption disorders (celiac disease, H. pylori, atrophic gastritis) 1

Hematology Referral Indications

Refer to hematology if:

• Refractory microcytic anemia despite adequate iron supplementation for 3 months 3
• Suspected genetic disorders (thalassemia, sideroblastic anemia, IRIDA) requiring genetic testing 3, 1
• Unexplained microcytosis with normal iron studies and no clear diagnosis after comprehensive workup 3