MLPAO Hematology and Coagulation Case Studies 2

Question 1

A patient has hemoglobin 70 g/L, MCV 110 fL, hypersegmented neutrophils, and elevated methylmalonic acid. What is the most likely diagnosis?

Accepted Answer

Vitamin B12 deficiency

Answer

Macrocytic anemia with hypersegmented neutrophils indicates megaloblastic anemia. The elevated methylmalonic acid (MMA) specifically distinguishes vitamin B12 deficiency from folate deficiency, as MMA requires B12-dependent methylmalonyl-CoA mutase. MMA is normal in folate deficiency but elevated in B12 deficiency.

Question 2

A patient has WBC 150 × 10⁹/L with a differential showing a full spectrum of myeloid maturation from blasts to mature neutrophils, basophilia, and splenomegaly. What is the most likely diagnosis?

Accepted Answer

Chronic myeloid leukemia

Answer

The hallmark of CML is an extremely elevated WBC with a complete spectrum of myeloid maturation ('pathological left shift'), basophilia, and massive splenomegaly. Unlike AML (blast predominance) or leukemoid reaction (no basophilia, positive LAP score), CML shows orderly maturation. Philadelphia chromosome/BCR-ABL1 testing confirms the diagnosis.

Question 3

A sample has a platelet count of 50 × 10⁹/L by impedance but the smear shows platelet clumps. What should the technologist do?

Accepted Answer

Recollect in a sodium citrate tube to rule out EDTA-dependent pseudothrombocytopenia

Answer

Platelet clumping in EDTA is a well-known cause of pseudothrombocytopenia. EDTA can cause antibody-mediated platelet clumping in some patients. Recollection in sodium citrate (blue-top) often resolves the clumping. The platelet count from the citrate tube must be multiplied by 1.1 to correct for the dilution factor.

Question 4

A patient has pancytopenia with 25% blasts in the peripheral blood. What is the most likely category of disease?

Accepted Answer

Acute leukemia

Answer

The presence of ≥20% blasts in peripheral blood or bone marrow defines acute leukemia (by WHO classification). Pancytopenia results from marrow replacement by leukemic blasts, suppressing normal hematopoiesis. Flow cytometry and cytogenetics are needed to classify as AML or ALL and determine prognosis.

Question 5

A patient taking unfractionated heparin develops a platelet drop from 250 to 100 × 10⁹/L on day 7 with a new DVT. The 4T score is 7. What is the next step?

Accepted Answer

Immediately stop all heparin, start alternative anticoagulant, and send HIT antibody testing

Answer

A high 4T score (6-8) with >50% platelet drop, timing on day 7, and new thrombosis strongly suggests HIT type II. All heparin must be stopped immediately (including flushes), an alternative non-heparin anticoagulant started (argatroban or fondaparinux), and HIT antibody testing sent. LMWH cross-reacts with HIT antibodies and is contraindicated.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Hematology and Coagulation Case Studies 2