Complete learning materials
Review each topic, apply the clinical case, then complete the linked ten-question assessment.
Clinical reasoning with a CBC
- Read hemoglobin, hematocrit, MCV, RDW, WBC differential and platelets together; use the local laboratory reference interval, age, pregnancy status and clinical context.
- Confirm unexpectedly critical findings, assess symptoms and compare with prior results. Do not interpret a single value in isolation.
- Classify anemia as microcytic, normocytic or macrocytic while recognizing mixed deficiencies may normalize MCV. Reticulocytes help distinguish low production from blood loss or hemolysis.
Microcytic and macrocytic patterns
- Microcytosis: evaluate ferritin and iron studies in context of inflammation; consider thalassemia when RBC count is relatively preserved and microcytosis is disproportionate.
- Macrocytosis: consider B12/folate deficiency, alcohol use, hepatic disease, hypothyroidism, medications and marrow disorders; examine smear and reticulocyte response.
- B12 deficiency with neurologic features warrants prompt clinical assessment; normal hemoglobin does not exclude clinically relevant deficiency.
White cells and platelets
- Neutrophilia may reflect infection, inflammation, corticosteroids or stress. Marked leukocytosis with blasts or systemic illness requires escalation.
- Neutropenia with fever is an urgent emergency concern, especially with immunosuppression.
- Interpret thrombocytopenia alongside bleeding, smear and possible pseudothrombocytopenia from platelet clumping; severe bleeding or suspected TTP needs emergency care.
Hemostasis and safety
- PT/INR and aPTT are pathway-oriented tests, not universal bleeding risk tests; indications include anticoagulant monitoring and selected bleeding disorders.
- Evaluate unexpected bleeding with medication review, platelet count, PT/aPTT, liver disease and targeted assessment.
- A peripheral smear can identify schistocytes and other clues; schistocytes with thrombocytopenia and organ injury are a medical emergency.
Applied clinical case
Case: A patient with fatigue has Hb 93 g/L, MCV 70 fL and low ferritin. Assess iron deficiency and investigate the cause of blood loss where appropriate, rather than assuming dietary deficiency alone.
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