What is the plan of care for a patient with microcytic anemia (small red blood cells) and elevated Red Cell Distribution Width (RDW)?

Plan of Care for Microcytic Anemia with Elevated RDW

This patient's laboratory values (MCH 23.7, MCHC 30.0, RDW 15.6) indicate microcytic hypochromic anemia with elevated RDW, which strongly suggests iron deficiency anemia and requires immediate confirmatory testing followed by investigation for the underlying cause. 1

Immediate Diagnostic Workup

Confirmatory Iron Studies

• Obtain serum ferritin as the most powerful confirmatory test, with <12 μg/dL being diagnostic of iron deficiency, though in the presence of inflammation, ferritin up to 100 μg/L may still indicate iron deficiency 1
• Measure transferrin saturation (<30% supports iron deficiency), serum iron (low in iron deficiency), and total iron binding capacity (increased in iron deficiency) 1
• Check C-reactive protein (CRP) to assess for concurrent inflammation that may affect ferritin interpretation 2

Diagnostic Significance of RDW

• The elevated RDW (15.6%, above the normal threshold of 14.0%) combined with microcytosis is highly indicative of iron deficiency anemia, with studies showing 90% sensitivity for iron deficiency when RDW is elevated 3, 4
• This pattern distinguishes iron deficiency from thalassemia trait, which typically presents with low or normal RDW due to homogeneous microcytic cells 2, 5

Investigation for Underlying Cause

Adult Men and Post-Menopausal Women

• Perform both upper and lower endoscopy to exclude gastrointestinal malignancy, as GI blood loss is the most common cause in this population 1, 2
• Evaluate for colonic cancer/polyps, NSAID use, gastric cancer, angiodysplasia, and inflammatory bowel disease 1
• Test for celiac disease with tissue transglutaminase antibodies, as malabsorption is an important treatable cause 1

Pre-Menopausal Women

• Assess menstrual blood loss history (quantity, duration, frequency), as this is the most common cause in this population 1
• If menstrual losses do not adequately explain the degree of anemia, proceed with GI evaluation as above 1
• Consider celiac disease screening 1

All Patients

• Obtain dietary history focusing on iron intake 1
• Review medications, particularly NSAIDs and anticoagulants 1

Treatment Protocol

Iron Supplementation

• Initiate oral iron supplementation as first-line treatment (typically ferrous sulfate 325 mg daily to three times daily) 1
• A therapeutic response to three weeks of oral iron confirms the diagnosis of iron deficiency 1
• For patients with inflammatory bowel disease or malabsorption, consider intravenous iron if oral therapy fails 1

Monitoring Response

• Recheck hemoglobin, MCV, and RDW after 4 weeks to assess response 1
• Continue iron therapy for 3-6 months after normalization of hemoglobin to replenish iron stores 1
• If no response after 4 weeks, reassess diagnosis, check adherence, and consider alternative diagnoses 1

Critical Pitfalls to Avoid

Do Not Miss Combined Deficiencies

• Combined iron, B12, or folate deficiency can mask typical findings and may present with normal MCV despite iron deficiency 1, 2
• If response to iron is suboptimal, check B12 and folate levels 1

Do Not Assume Thalassemia Without Testing

• While thalassemia trait typically has low RDW, some patients with beta-thalassemia trait can have elevated RDW (66% in one study) 4
• Never give iron supplementation for presumed thalassemia without documenting iron status with ferritin, as this can cause iron overload 2
• If ferritin is normal/high and RDW remains elevated, obtain hemoglobin electrophoresis 2

Do Not Overlook Anemia of Chronic Disease

• Anemia of chronic disease can coexist with iron deficiency, particularly in patients with inflammatory conditions 1, 2
• In these patients, ferritin may be falsely elevated; transferrin saturation <30% and elevated CRP suggest combined pathology 1

Do Not Delay Malignancy Workup

• Even mild anemia warrants investigation in adult men and post-menopausal women, as severity does not correlate with likelihood of serious underlying disease 2
• The presence of iron deficiency in these populations mandates endoscopic evaluation regardless of symptom severity 2