ABIM Hematology

Question 1

Which lab pattern is most consistent with iron deficiency anemia?

Accepted Answer

Low ferritin, high TIBC

Answer

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?

Accepted Answer

Start argatroban

Answer

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?

Accepted Answer

ADAMTS13 activity

Answer

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?

Accepted Answer

Elevated methylmalonic acid

Answer

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?

Accepted Answer

Direct oral anticoagulant (e.g., apixaban)

Answer

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.

ABIM - American Board of Internal Medicine Practice Test

ABIM - American Board of Internal Medicine Practice Test

ABIM Hematology