Medical Laboratory Technician Exam Medical Laboratory Technician Hematology and Coagulation 1

Question 1

A peripheral blood smear shows target cells, sickle-shaped erythrocytes, and Howell-Jolly bodies. Which condition is most consistent with these findings?

Accepted Answer

Sickle cell disease with functional asplenia

Answer

Sickle cell disease causes sickling of RBCs under low-oxygen conditions. Repeated splenic infarctions lead to functional asplenia, allowing Howell-Jolly bodies (nuclear remnants normally removed by the spleen) to persist. Target cells are also characteristic of hemoglobin S disorders.

Question 2

Which platelet function test measures the time it takes for a platelet plug to form in a standardized capillary tube using whole blood, and is sensitive to both platelet number and vWF activity?

Accepted Answer

PFA-100 closure time

Answer

The PFA-100 (Platelet Function Analyzer-100) measures closure time using collagen/ADP or collagen/epinephrine cartridges. It is sensitive to defects in platelet number, platelet function, and von Willebrand factor, making it a useful initial screening tool for primary hemostasis disorders.

Question 3

A 35-year-old woman presents with recurrent miscarriages and a prolonged aPTT that does not correct on a 1:1 mix with normal plasma. Platelet count is normal. Which diagnosis should be suspected?

Accepted Answer

Lupus anticoagulant

Answer

Lupus anticoagulant is an antiphospholipid antibody that prolongs phospholipid-dependent clotting tests (aPTT) in vitro. Crucially, it does not correct on a 1:1 mix because it is an inhibitor, not a factor deficiency. It is associated with thrombosis and recurrent pregnancy loss despite prolonging the aPTT.

Question 4

In the coagulation cascade, which factor acts as the common pathway 'entry point' activated by both the intrinsic (contact) and extrinsic (tissue factor) pathways?

Accepted Answer

Factor X

Answer

Factor X (Stuart-Prower factor) is the junction where both pathways converge. The intrinsic pathway activates Factor X via the tenase complex (IXa + VIIIa), while the extrinsic pathway activates it via the extrinsic tenase complex (TF + VIIa). Activated Factor Xa then combines with Factor Va to form prothrombinase.

Question 5

A complete blood count reveals WBC 95 × 10⁹/L with 85% lymphocytes, many of which appear small and mature with scant cytoplasm and smudge cells on smear. RBC and platelets are mildly reduced. Which diagnosis is most likely?

Accepted Answer

Chronic lymphocytic leukemia (CLL)

Answer

CLL is characterized by a marked lymphocytosis of small, mature-appearing lymphocytes and is the most common adult leukemia. Smudge cells (ruptured lymphocytes during smear preparation due to fragile cytoplasm) are a hallmark finding. ALL typically presents with blasts, not mature-appearing cells.

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Medical Laboratory Technician Hematology and Coagulation 1