Anemia: A Comprehensive Guide for MCCQE1
Introduction
Anemia is one of the most common clinical presentations encountered in Canadian medical practice, affecting a wide demographic from pediatric populations to the elderly. For MCCQE1 preparation, understanding the physiological basis, diagnostic approach, and management of anemia is critical.
In the context of the CanMEDS framework, managing anemia requires the role of a Medical Expert to diagnose correctly, but also a Health Advocate to address underlying social determinants of health (e.g., nutrition availability in remote Indigenous communities) and a Resource Steward to utilize blood products and investigations wisely.
Definition
Anemia is defined as a reduction in red blood cell (RBC) mass. practically defined by the World Health Organization (WHO) and widely accepted in Canada as:
- Men: Hemoglobin (Hb) < 130 g/L
- Non-pregnant Women: Hb < 120 g/L
- Pregnant Women: Hb < 110 g/L
Classification and Approach
The most effective way to approach anemia for the MCCQE1 is morphologic, based on the Mean Corpuscular Volume (MCV).
Microcytic (<80 fL)
Microcytic Anemia is characterized by small RBCs. It is usually due to a defect in hemoglobin synthesis (heme or globin).
- Iron Deficiency Anemia (IDA): Most common cause globally and in Canada.
- Thalassemia: Globin chain defects.
- Anemia of Chronic Disease (ACD): Early stages can be normocytic; late stages microcytic.
- Sideroblastic Anemia: Defect in heme synthesis (e.g., lead poisoning, alcohol, myelodysplasia).
Mnemonic for Microcytic Anemia (TAILS)
A classic mnemonic useful for Canadian medical students:
- T - Thalassemia
- A - Anemia of Chronic Disease
- I - Iron Deficiency
- L - Lead Poisoning
- S - Sideroblastic Anemia
Diagnostic Workup
Follow this step-by-step approach to evaluating a patient with anemia.
Step 1: History and Physical Examination
Focus on signs of bleeding (melena, menorrhagia), diet (veganism), alcohol intake, and family history.
- Physical Exam: Pallor, jaundice (hemolysis), koilonychia (spoon nails - iron deficiency), glossitis (B12/Iron), neurological changes (B12).
Step 2: Complete Blood Count (CBC) and Smear
Look at the Hb (severity), MCV (classification), and RDW (Red Cell Distribution Width).
- High RDW suggests Iron Deficiency (anisocytosis).
- Normal RDW suggests Thalassemia.
- Peripheral Smear: Look for specific shapes (e.g., bite cells in G6PD, spherocytes in Hereditary Spherocytosis, hypersegmented neutrophils in megaloblastic anemia).
Step 3: Reticulocyte Count
This determines if the bone marrow is responding appropriately.
- Corrected Reticulocyte Count > 2% (or absolute count high) indicates hemolysis or blood loss.
- Low count indicates production failure.
Step 4: Specific Metabolic Studies
Based on MCV:
- Microcytic: Ferritin, TIBC, Iron Saturation.
- Macrocytic: B12, RBC Folate, TSH, Liver enzymes.
- Normocytic: Creatinine (renal), Coombs test (if hemolysis suspected).
Interpreting Iron Studies
Differentiation between Iron Deficiency Anemia (IDA) and Anemia of Chronic Disease (ACD) is a high-yield MCCQE1 topic.
| Parameter | Iron Deficiency Anemia | Anemia of Chronic Disease | Thalassemia Trait |
|---|---|---|---|
| MCV | Low | Low or Normal | Very Low |
| Ferritin | Low (<30 ug/L) | Normal or High (Acute phase reactant) | Normal or High |
| TIBC | High | Low | Normal |
| Transferrin Saturation | Low (<20%) | Low or Normal | Normal or High |
| RDW | High | Normal | Normal |
MCCQE1 Tip: Ferritin is the most specific test for iron deficiency. However, because ferritin is an acute-phase reactant, it can be falsely elevated in inflammation. If ferritin is “normal” (e.g., 50-100 ug/L) but inflammation is present, IDA is not ruled out.
High-Yield Specific Anemias
1. Iron Deficiency Anemia (IDA)
- Etiology:
- Adult Men/Post-menopausal Women: GI blood loss (malignancy, ulcer, angiodysplasia) until proven otherwise.
- Reproductive Age Women: Menorrhagia.
- Children/Elderly: Nutritional deficiency (tea/coffee inhibits absorption).
- Management:
- Oral Iron (Ferrous fumarate/sulfate). Key: Take with Vitamin C (orange juice) to enhance absorption; avoid calcium/antacids.
- IV Iron (Monoferric, Venofer) if intolerant to oral or rapid correction needed.
- Treat the underlying cause (e.g., rule out colon cancer).
2. Vitamin B12 Deficiency
- Etiology: Pernicious anemia (Anti-intrinsic factor antibodies), terminal ileum resection, vegan diet.
- Features: Macrocytic anemia, neurological symptoms (paresthesias, subacute combined degeneration of the cord - loss of vibration/proprioception).
- Diagnosis: Low B12. If borderline, check Methylmalonic Acid (MMA) (High in B12 deficiency).
- Treatment: IM B12 (Cyanocobalamin) or high-dose oral B12.
3. Hemolytic Anemias
- Labs: Increased LDH, Increased Unconjugated Bilirubin, Decreased Haptoglobin, Increased Reticulocytes.
- Immune: Positive Direct Coombs Test (Autoimmune Hemolytic Anemia).
- Non-Immune: Microangiopathic (TTP/HUS/DIC) - look for Schistocytes.
Canadian Guidelines & Choosing Wisely
Understanding Canadian-specific practice patterns is essential for the MCCQE1.
Choosing Wisely Canada: Transfusion
Transfusion Thresholds
Don’t transfuse red blood cells for iron deficiency anemia without hemodynamic instability.
- Restrictive Strategy: For stable, non-bleeding hospitalized patients, transfuse only if Hb < 70 g/L.
- Target: Maintain Hb 70-90 g/L. Single unit transfusions are preferred (“One and done”, then reassess).
Screening in Pregnancy
Canadian guidelines recommend screening all pregnant women for anemia (CBC) in the first trimester and at 24-28 weeks. Routine iron supplementation is not universal but recommended for those with ferritin < 30 ug/L.
Indigenous Health Considerations
Be aware of higher prevalence of nutritional anemia in remote communities due to food insecurity (high cost of perishable foods). Also, recognize that H. pylori infection (causing gastritis and malabsorption of iron) is more prevalent in some Northern populations.
Key Points to Remember for MCCQE1
-
Checklist for Study:
- Differentiate Micro/Normo/Macro based on MCV.
- Memorize the iron study patterns for IDA vs. ACD.
- Recognize “Pancytopenia” requires a bone marrow biopsy (rule out Leukemia/Aplastic Anemia).
- Identify neurological signs as unique to B12 deficiency (vs. Folate).
- Remember: In an elderly patient with new IDA, Colonoscopy is the mandatory next step, even if they have hemorrhoids.
-
Formulas:
Transferrin Saturation = (Serum Iron / TIBC) x 100
Sample Question
Clinical Scenario
A 68-year-old male presents to his family physician complaining of increasing fatigue and shortness of breath on exertion over the past 3 months. He has no chest pain. Past medical history is significant for osteoarthritis, for which he takes naproxen occasionally. He denies melena or hematochezia.
Vitals: BP 130/80 mmHg, HR 92 bpm, RR 18/min. Physical Exam: Conjunctival pallor is noted. Abdomen is soft and non-tender. No organomegaly. Labs:
- Hemoglobin: 85 g/L
- MCV: 72 fL
- Ferritin: 8 ug/L
- Platelets: 450 x 10^9/L
Which one of the following is the most appropriate next step in the management of this patient?
- A. Prescribe oral ferrous sulfate and recheck hemoglobin in 3 months
- B. Order a colonoscopy and gastroscopy
- C. Transfuse 1 unit of packed red blood cells
- D. Reassure the patient that this is a side effect of naproxen and discontinue the medication
- E. Order a bone marrow biopsy
Explanation
The correct answer is:
- B. Order a colonoscopy and gastroscopy
Detailed Explanation: This patient presents with a classic picture of Iron Deficiency Anemia (IDA) in an elderly male, evidenced by microcytic anemia (MCV < 80 fL), low ferritin (diagnostic of IDA), and reactive thrombocytosis (elevated platelets are common in active bleeding/IDA).
- Option B (Correct): In any man or post-menopausal woman with confirmed iron deficiency anemia, gastrointestinal malignancy must be ruled out regardless of the presence or absence of overt bleeding symptoms. The use of NSAIDs (naproxen) also raises the possibility of peptic ulcer disease or gastritis. Therefore, endoscopic evaluation (upper and lower) is the standard of care.
- Option A (Incorrect): While iron replacement is part of the treatment, it is negligent to treat the anemia without identifying the underlying cause in this demographic. Delaying diagnosis of a potential colorectal cancer is a critical error.
- Option C (Incorrect): Per Choosing Wisely Canada, transfusion is generally reserved for patients with Hb < 70 g/L or those who are hemodynamically unstable/symptomatic with chest pain. This patient is stable.
- Option D (Incorrect): While NSAIDs can cause bleeding, assuming this is the sole cause without visualization is dangerous.
- Option E (Incorrect): Bone marrow biopsy is invasive and reserved for cases where the cause is unclear after non-invasive workup or if aplastic anemia/leukemia is suspected (usually associated with pancytopenia, not isolated anemia with thrombocytosis).
References
- Medical Council of Canada. (n.d.). MCCQE Part I Clinical Decision-Making and Multiple-Choice Questions Objectives. Retrieved from mcc.ca.
- Choosing Wisely Canada. (2023). Transfusion Medicine: Ten Things Physicians and Patients Should Question. Retrieved from choosingwiselycanada.org.
- Goldman, L., & Schafer, A. I. (2020). Goldman-Cecil Medicine (26th ed.). Elsevier.
- BC Guidelines. (2019). Iron Deficiency - Investigation and Management. Guidelines & Protocols Advisory Committee.
- Toronto Notes. (2023). Hematology Chapter. Toronto Notes for Medical Students, Inc.