What is the appropriate management for a patient with elevated RDW and MPV in the context of a normal CBC?

Management of Elevated RDW and MPV with Otherwise Normal CBC

In a patient with isolated elevations of RDW (15.5%) and MPV (12.1 fL) but otherwise normal complete blood count parameters, the appropriate management is to obtain serum ferritin, transferrin saturation, vitamin B12, folate, and CRP to identify occult iron deficiency, early vitamin deficiency, or underlying inflammation before these conditions manifest as overt anemia. 1

Initial Diagnostic Approach

The combination of elevated RDW with elevated MPV in the context of normal hemoglobin and cell counts represents an early warning pattern that warrants investigation rather than reassurance:

• Elevated RDW (15.5%) indicates increased variation in red blood cell sizes (anisocytosis), which most commonly reflects early nutritional deficiency states, mixed deficiency patterns, or chronic inflammation before frank anemia develops 1

• Elevated MPV (12.1 fL) suggests increased platelet turnover or activation, which can accompany inflammatory conditions, though its clinical significance is less established than RDW 2, 3

• The normal hemoglobin (implied by "normal CBC") does not exclude early or evolving hematologic abnormalities, as RDW typically rises before hemoglobin falls in deficiency states 1

Essential Laboratory Workup

Order the following tests to identify the underlying cause:

• Serum ferritin and transferrin saturation to detect iron deficiency (ferritin <30 μg/L confirms deficiency; <100 μg/L with inflammation may still indicate deficiency; transferrin saturation <30% supports iron deficiency) 4, 1

• Vitamin B12 and folate levels to identify macrocytic deficiency states that can present with elevated RDW before MCV rises 1

• C-reactive protein (CRP) to assess for inflammation, which affects ferritin interpretation and can cause elevated RDW through anemia of chronic disease 4, 1, 3

• Reticulocyte count to distinguish between decreased production (deficiency states, bone marrow disorders) versus increased destruction or loss (hemolysis, bleeding) 1

Interpretation Algorithm

If reticulocytes are low or normal:

• Consider early vitamin B12 or folate deficiency, evolving iron deficiency, combined deficiencies, early myelodysplastic syndrome, or medication effects 1
• The normal hemoglobin suggests you are catching the process early, before overt anemia develops 1

If reticulocytes are elevated:

• Consider compensated hemolytic process, recent occult bleeding with marrow response, or early recovery from acute blood loss 1
• Add haptoglobin and LDH to assess for hemolysis 1

If ferritin is low (<30 μg/L or <100 μg/L with inflammation):

• Initiate iron supplementation and investigate the source of iron loss, particularly gastrointestinal bleeding in men and postmenopausal women 4, 1
• Both upper and lower endoscopy should be performed to exclude malignancy in these populations 5

If vitamin B12 is low:

• Immediate treatment is critical to prevent irreversible neurologic damage 1

Clinical Context Considerations

The specific pattern in this patient (neutrophils 42.5%, lymphocytes 44.5%) shows a relative lymphocytosis that is still within normal range but may suggest:

• Chronic inflammatory or autoimmune conditions where RDW correlates with disease activity 3, 6
• Viral recovery states
• Early nutritional deficiency affecting both red cell and potentially immune function 4

Common pitfalls to avoid:

• Do not dismiss elevated RDW as clinically insignificant simply because hemoglobin is normal—RDW rises early in deficiency states and inflammatory conditions 1, 6

• Do not attribute findings to "normal variation" without excluding treatable causes, as early intervention prevents progression to symptomatic anemia 1

• Do not overlook combined deficiencies (e.g., iron plus B12 or folate), which can result in normal MCV and hemoglobin despite significant depletion of multiple nutrients 1, 5

When to Refer to Hematology

Immediate hematology consultation is required if:

• The cause remains unclear after complete workup 1
• There is no response to appropriate vitamin or iron replacement after 2-3 weeks 1
• Suspicion for myelodysplastic syndrome arises (particularly in older patients with unexplained cytopenias or dysplastic features) 1
• Pancytopenia develops 1

Monitoring Strategy

After initiating treatment based on laboratory findings:

• Repeat CBC with RDW in 4-6 weeks to confirm response to therapy 4
• RDW should normalize with successful treatment of the underlying deficiency 1
• Persistent elevation despite adequate replacement warrants hematology evaluation 1