Do an RBC count of 3.72 ×10⁶/µL, hematocrit 33.2 %, and hemoglobin 11.1 g/dL indicate anemia, and what work‑up is recommended?

Anemia Diagnosis and Recommended Work-Up

Yes, these values indicate anemia, and you should initiate a systematic work-up starting with mean corpuscular volume (MCV), reticulocyte count, serum ferritin, transferrin saturation, and C-reactive protein (CRP).

Confirming Anemia

Your patient's hemoglobin of 11.1 g/dL and hematocrit of 33.2% both fall below the WHO-defined thresholds for anemia 1. The RBC count of 3.72 ×10⁶/µL is also reduced. These values definitively establish anemia regardless of the patient's sex, as they fall below cutoffs for both women (Hb <12.0 g/dL, Hct <36%) and men (Hb <13.0 g/dL, Hct <39%) 1.

Essential Initial Work-Up

The minimum diagnostic work-up must include 1:

• Complete blood count with red cell indices - specifically MCV and red cell distribution width (RDW)
• Reticulocyte count - to assess bone marrow response
• Serum ferritin - the most powerful test for iron deficiency 2
• Transferrin saturation - to evaluate available iron for erythropoiesis
• CRP concentration - to detect inflammation that affects ferritin interpretation

Morphologic Classification Approach

Use the MCV to categorize the anemia 3:

• Microcytic (MCV <80 fL): Most commonly iron deficiency; also consider thalassemia, anemia of chronic disease, or sideroblastic anemia
• Normocytic (MCV 80-100 fL): Suggests hemorrhage, hemolysis, bone marrow failure, chronic inflammation, or renal insufficiency
• Macrocytic (MCV >100 fL): Indicates vitamin B12 or folate deficiency (megaloblastic), or less commonly alcoholism, myelodysplastic syndrome, or certain drugs

Kinetic Assessment

The reticulocyte index (RI) distinguishes production versus destruction problems 3:

• Low RI (<1.0): Decreased RBC production from iron deficiency, vitamin B12/folate deficiency, aplastic anemia, or bone marrow dysfunction
• High RI (>2.0): Normal/increased production suggests blood loss or hemolysis

Iron Status Interpretation

Critical caveat: Ferritin interpretation depends on inflammatory status 1:

• Without inflammation: Ferritin <30 μg/L indicates iron deficiency
• With inflammation present: Ferritin up to 100 μg/L may still represent iron deficiency, as inflammation falsely elevates ferritin
• Transferrin saturation <15% supports absolute iron deficiency 3

Extended Work-Up When Indicated

If the cause remains unclear after initial testing, obtain 1:

• Vitamin B12 and folate levels (if macrocytic)
• Haptoglobin, lactate dehydrogenase, indirect bilirubin (if hemolysis suspected)
• Creatinine and glomerular filtration rate (if renal disease suspected)
• Stool guaiac or endoscopy (if gastrointestinal bleeding suspected)
• Coombs test (if autoimmune hemolysis suspected)

Population-Specific Considerations

For postmenopausal women and all men: Upper and lower gastrointestinal investigations should be considered to exclude malignancy, as colorectal and gastric cancers are critical causes 2. All patients should be screened for celiac disease 2.

For premenopausal women: Screen for celiac disease, but additional GI investigations depend on clinical judgment, severity of anemia, and menstrual history 2.

Common Pitfalls to Avoid

• Don't assume anemia equals iron deficiency - only 37% of anemic women and 25% of anemic children are actually iron deficient 4
• Don't rely on the "rule of 3" (Hct = 3 × Hb) - this relationship is not accurate and varies with age 5
• Don't ignore inflammation - it elevates ferritin and can mask true iron deficiency 1
• Don't skip the peripheral blood smear - visual confirmation of RBC morphology is critical 3

The lower the hemoglobin, the more urgent the investigation, as severe anemia correlates with serious underlying pathology 2.