How to diagnose and manage anemia in an adult with low hemoglobin and hematocrit?

Diagnosis and Management of Anemia with Hemoglobin 11.1 g/dL

This patient has confirmed anemia requiring immediate diagnostic workup, with the laboratory pattern (low MCH 26.9, microcytic picture) strongly suggesting iron deficiency as the primary etiology that must be confirmed with serum ferritin testing.

Confirming the Diagnosis of Anemia

Gender-specific thresholds determine anemia diagnosis:

• If this patient is male: Hemoglobin 11.1 g/dL is clearly anemic (threshold <13.5 g/dL for adult males) 1
• If this patient is female: Hemoglobin 11.1 g/dL is also anemic (threshold <12.0 g/dL for adult females) 1
• The World Health Organization defines anemia as Hb <130 g/L in men and <120 g/L in non-pregnant women, confirming this patient meets criteria regardless of sex 2, 3

Interpreting the Red Blood Cell Indices

The MCH of 26.9 pg is reduced and highly suggestive of iron deficiency:

• Low MCH has high sensitivity (97-100%) for identifying iron-deficient anemic individuals and is more reliable than MCV alone for diagnosing iron deficiency 2, 3
• MCH is less dependent on storage conditions and equipment variability, making it a superior marker 3
• The RDW of 14.3% (elevated) indicates increased variation in red cell size, consistent with evolving iron deficiency 4

However, low MCH alone is not diagnostic and requires ferritin confirmation before proceeding with treatment or investigation 2

Mandatory Next Step: Serum Ferritin Testing

Order serum ferritin immediately to confirm iron deficiency:

• Ferritin <15 μg/L is highly specific (specificity 0.99) for absolute iron deficiency 2, 3
• Ferritin <30 μg/L indicates low body iron stores 2, 3
• Ferritin <45 μg/L is the optimal diagnostic cutoff (specificity 0.92), especially if inflammation is suspected 2, 3
• Ferritin >150 μg/L makes absolute iron deficiency unlikely, even with concurrent inflammation 2, 3

Additional iron studies to order concurrently:

• Serum iron (normal 50-175 μg/dL) and transferrin saturation (normal 20-50%) 3
• Total iron binding capacity (TIBC, normal 250-370 μg/dL; elevated in iron deficiency) 3

Alternative Diagnoses to Consider

If ferritin is normal or elevated, obtain hemoglobin electrophoresis:

• Microcytosis with normal iron studies suggests thalassemia trait, particularly in patients of Mediterranean, African, Middle Eastern, or Southeast Asian descent 2
• This is critical to avoid misdiagnosing and inappropriately treating with iron 2

If the patient has chronic kidney disease:

• Anemia evaluation should be initiated at these hemoglobin levels regardless of CKD stage 1
• The severity of anemia correlates with both GFR decline and underlying kidney disease etiology 1

Management Based on Ferritin Results

If ferritin confirms iron deficiency (<45 μg/L):

Investigate the underlying cause based on patient demographics:

• Men of any age: Require gastrointestinal endoscopy (upper and lower) to exclude malignancy or bleeding source 4
• Postmenopausal women: Require gastrointestinal endoscopy similar to men 2, 4
• Premenopausal women: GI investigation generally not warranted unless patient has GI symptoms, family history of GI malignancy, or fails to respond to iron therapy 2
• Pregnant women: Screen routinely and treat, as pregnancy is a common cause of iron deficiency 4

Initiate oral iron replacement therapy:

• Start supplemental iron while awaiting or conducting further workup 4
• A therapeutic trial is both diagnostic and therapeutic: hemoglobin rise ≥10 g/L within 2 weeks strongly confirms absolute iron deficiency, even if iron studies were equivocal 2, 3
• If patient cannot tolerate or absorb oral iron, consider parenteral iron therapy 4

Common Pitfalls to Avoid

Do not treat empirically without ferritin confirmation:

• Low MCH suggests but does not diagnose iron deficiency; ferritin is mandatory 2
• Treating thalassemia trait with iron is inappropriate and potentially harmful 2

Do not skip malignancy workup in appropriate populations:

• Men and postmenopausal women with confirmed iron deficiency anemia require endoscopic evaluation regardless of symptom presence 4
• Iron deficiency in these populations may be the only presenting sign of gastrointestinal malignancy 4

Recognize that inflammation affects ferritin interpretation:

• Ferritin is an acute phase reactant; standard cutoffs become unreliable in inflammatory conditions 3
• Consider higher ferritin thresholds (up to 45 μg/L) or additional markers like soluble transferrin receptor in patients with chronic disease 3