Medical Laboratory TechnicianĀ Exam Medical Laboratory Technician Hematology and Coagulation 1 ā Questions and Answers
Question 1: A peripheral blood smear shows target cells, sickle-shaped erythrocytes, and Howell-Jolly bodies. Which condition is most consistent with these findings?
- Iron deficiency anemia
- Sickle cell disease with functional asplenia (Correct answer)
- Hereditary spherocytosis
- Warm autoimmune hemolytic anemia
Correct answer: Sickle cell disease with functional asplenia
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?
- Platelet aggregation study
- PFA-100 closure time (Correct answer)
- Ristocetin cofactor assay
- Thromboelastography (TEG)
Correct answer: PFA-100 closure time
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?
- Hemophilia A
- Factor XII deficiency
- Lupus anticoagulant (Correct answer)
- Vitamin K deficiency
Correct answer: Lupus anticoagulant
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?
- Factor VII
- Factor X (Correct answer)
- Factor IX
- Factor XI
Correct answer: Factor X
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 Ć 10ā¹/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?
- Acute lymphoblastic leukemia (ALL)
- Chronic lymphocytic leukemia (CLL) (Correct answer)
- Infectious mononucleosis
- Hairy cell leukemia
Correct answer: Chronic lymphocytic leukemia (CLL)
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.
Question 6: A patient on warfarin therapy has an INR of 5.8 with active bleeding. Which product provides the most rapid reversal of warfarin's anticoagulant effect?
- Fresh frozen plasma (FFP)
- Vitamin K (IV)
- 4-factor prothrombin complex concentrate (4F-PCC) (Correct answer)
- Cryoprecipitate
Correct answer: 4-factor prothrombin complex concentrate (4F-PCC)
4-factor PCC (containing Factors II, VII, IX, and X) provides immediate reversal of warfarin by directly replacing all vitamin K-dependent clotting factors. It acts faster than FFP (no thawing delay, smaller volume) and far faster than IV Vitamin K, which requires hours for hepatic synthesis of new factors. Cryoprecipitate does not contain the relevant factors.
Medical Laboratory TechnicianĀ Exam Medical Laboratory Technician Hematology and Coagulation 1
A peripheral blood smear shows target cells, sickle-shaped erythrocytes, and Howell-Jolly bodies.
Which condition is most consistent with these findings?