ABIM Hematology — Questions and Answers
Question 1: Which lab pattern is most consistent with iron deficiency anemia?
- High ferritin, low TIBC
- Normal ferritin, high MCV
- Low ferritin, high TIBC (Correct answer)
- High ferritin, high transferrin saturation
Correct answer: Low ferritin, high TIBC
Iron deficiency causes low ferritin (low iron stores) and a high TIBC (more transferrin). Transferrin saturation is low and MCV is usually low. High ferritin with low TIBC suggests anemia of inflammation.
Question 2: On day 7 of unfractionated heparin, a patient's platelets drop 60% and a new DVT develops. After stopping heparin, what is the most appropriate next step?
- Switch to enoxaparin
- Transfuse platelets
- Start warfarin immediately
- Start argatroban (Correct answer)
Correct answer: Start argatroban
Suspected heparin-induced thrombocytopenia (HIT) with thrombosis requires a non-heparin anticoagulant such as argatroban, bivalirudin, or fondaparinux. LMWH cross-reacts with HIT antibodies. Starting warfarin alone can cause venous limb gangrene, and platelet transfusion is generally avoided.
Question 3: A patient has fever, confusion, thrombocytopenia, schistocytes on smear, and elevated LDH. Which underlying deficiency is most likely?
- ADAMTS13 activity (Correct answer)
- Factor VIII
- Antithrombin III
- Protein C
Correct answer: ADAMTS13 activity
Thrombotic thrombocytopenic purpura (TTP) results from severely reduced ADAMTS13 activity, usually from an autoantibody. Ultra-large von Willebrand multimers build up and cause microangiopathic hemolytic anemia. Urgent plasma exchange is the mainstay of treatment.
Question 4: A patient has macrocytic anemia. Which lab result best distinguishes vitamin B12 deficiency from folate deficiency?
- Elevated homocysteine
- Elevated methylmalonic acid (Correct answer)
- Hypersegmented neutrophils
- Elevated MCV
Correct answer: Elevated methylmalonic acid
Both deficiencies raise homocysteine and cause hypersegmented neutrophils and macrocytosis. Only B12 deficiency raises methylmalonic acid, because B12 is the cofactor for methylmalonyl-CoA mutase.
Question 5: A 50-year-old without cancer has an acute proximal DVT and normal renal function. Which anticoagulant class do CHEST guidelines suggest over warfarin?
- Unfractionated heparin long-term
- Aspirin
- Direct oral anticoagulant (e.g., apixaban) (Correct answer)
- No anticoagulation; compression stockings only
Correct answer: Direct oral anticoagulant (e.g., apixaban)
For VTE without cancer, CHEST guidelines suggest a direct oral anticoagulant (apixaban, rivaroxaban, dabigatran, or edoxaban) over a vitamin K antagonist. DOACs have similar efficacy, less major bleeding, and do not need INR monitoring. Treatment lasts at least 3 months.
Question 6: A 45-year-old man has elevated transferrin saturation and ferritin and is homozygous for HFE C282Y. What is the first-line treatment?
- Therapeutic phlebotomy (Correct answer)
- Oral deferasirox
- Liver transplantation
- Dietary iron restriction alone
Correct answer: Therapeutic phlebotomy
Therapeutic phlebotomy is first-line for hereditary hemochromatosis with iron overload. The usual target is a ferritin of about 50–100 ng/mL. Chelators are reserved for patients who cannot tolerate phlebotomy, such as those with anemia.
