What is the appropriate management for a patient with anemia, low MCHC, and high RDW?

Management of Anemia with Low MCHC and High RDW

This patient requires immediate iron studies (serum ferritin, transferrin saturation, TIBC) and comprehensive gastrointestinal evaluation to identify the underlying cause of what appears to be iron deficiency anemia. 1

Diagnostic Interpretation

Your laboratory findings reveal:

• Anemia: Hemoglobin 10.4 g/dL (below normal for both men and women) 1
• Low MCHC (29.1): Indicates hypochromic red blood cells, characteristic of iron deficiency 2
• Elevated RDW (17.0% and 58.8 SD): Reflects significant red cell size variation (anisocytosis), highly suggestive of iron deficiency 3, 2
• Normal MCV (94.0): Does not exclude iron deficiency, as 35% of patients with pernicious anemia and nearly half of iron-deficient patients can have normal MCV 4, 5

The combination of low MCHC with high RDW has 73% sensitivity for detecting iron deficiency, making this the most sensitive screening parameter available 3, 2. The normal MCV should not provide false reassurance—combined deficiencies (iron plus B12/folate) can mask each other and produce a normal MCV with elevated RDW 6.

Immediate Diagnostic Workup

Iron Studies (obtain immediately):

• Serum ferritin: <30 μg/L confirms iron deficiency in the absence of inflammation; <100 μg/L suggests iron deficiency when inflammation is present 6, 1
• Transferrin saturation: <20% indicates iron deficiency 6
• Total iron-binding capacity 1

Additional Essential Tests:

• Reticulocyte count to assess bone marrow response and distinguish regenerative from non-regenerative anemia 6, 1
• C-reactive protein (CRP) to evaluate for anemia of chronic disease 6, 1
• Vitamin B12 and folate levels (given normal MCV with high RDW, suggesting possible combined deficiency) 6, 1
• Serum creatinine to exclude renal causes 6, 1
• Celiac serology (tissue transglutaminase antibody), particularly important in premenopausal women 1

Gastrointestinal Evaluation

Both upper and lower GI investigations are mandatory for adults with new iron deficiency anemia without obvious explanation 1:

• Upper endoscopy with duodenal biopsies: Evaluate for peptic ulcer disease, gastritis, celiac disease, gastric cancer, and NSAID-related damage 6, 1
• Colonoscopy: Exclude colorectal cancer, polyps, angiodysplasia, and inflammatory bowel disease 6, 1

This dual evaluation is critical because 10-15% of patients have pathology in both upper and lower GI tracts 1. Document any NSAID or aspirin use and discontinue if possible 6.

Iron Replacement Therapy

Initiate oral iron supplementation immediately while awaiting diagnostic workup 1:

• First-line: Ferrous sulfate 325 mg (65 mg elemental iron) two to three times daily 1
• Treatment duration: Continue for 3 months after hemoglobin normalization to replenish iron stores 1
• Expected response: Hemoglobin should increase by at least 2 g/dL within 4 weeks 6

Parenteral iron indications:

• Intolerance to oral iron (GI side effects occur commonly) 1
• Malabsorption (celiac disease, inflammatory bowel disease) 6
• Inadequate response to oral therapy after 4 weeks 6
• Active inflammation with elevated hepcidin (impairs oral iron absorption) 6

Critical Red Flags

Urgent evaluation required if:

• Hemoglobin <7.5 g/dL or hemodynamic instability 1
• Alarm symptoms: unintentional weight loss, dysphagia, melena, hematochezia 1
• Men with hemoglobin <12 g/dL or postmenopausal women with hemoglobin <10 g/dL warrant more urgent investigation 1

Transfusion threshold: Reserve blood transfusions for patients with or at risk of cardiovascular instability; use restrictive strategy (hemoglobin <7-8 g/dL) 1

Common Pitfalls to Avoid

• Do not assume dietary insufficiency alone: Even with positive dietary history, complete GI investigation remains mandatory 6
• Do not rely on MCV alone: Normal MCV occurs in 35% of deficiency states and does not exclude iron deficiency 4, 5
• Do not overlook combined deficiencies: Normal MCV with high RDW suggests coexisting iron and B12/folate deficiency 6
• Do not stop at ferritin >100 μg/L: In the presence of inflammation (check CRP), ferritin up to 100 μg/L can still represent iron deficiency 6