Medical Laboratory Technician Hematology and Coagulation Questions and Answers — Questions and Answers
Question 1: A patient is receiving unfractionated heparin therapy for deep vein thrombosis. The clinical protocol requires maintaining the aPTT at 1.5 to 2.5 times the mean of the normal range. The laboratory's normal aPTT range is 28-38 seconds. Which of the following results is within the therapeutic range for this patient?
- 40 seconds
- 80 seconds (Correct answer)
- 100 seconds
- 25 seconds
Correct answer: 80 seconds
The mean of the normal range is (28+38)/2 = 33 seconds. The therapeutic range is 1.5 to 2.5 times this mean. Therefore, the lower limit is 33 * 1.5 = 49.5 seconds, and the upper limit is 33 * 2.5 = 82.5 seconds. A result of 80 seconds falls within this therapeutic window.
Question 2: A peripheral blood smear shows red blood cells arranged in stacks, resembling coins. This finding is best described as:
- Agglutination
- Spherocytosis
- Rouleaux (Correct answer)
- Anisocytosis
Correct answer: Rouleaux
Rouleaux formation is the stacking of erythrocytes, which is often seen in conditions with increased plasma proteins, such as multiple myeloma. Agglutination involves irregular clumping of red cells due to antibodies. Spherocytosis refers to spherical red cells, and anisocytosis indicates variation in red cell size.
Question 3: Which of the following laboratory tests is most crucial for monitoring the effectiveness of warfarin (Coumadin®) therapy?
- Activated Partial Thromboplastin Time (aPTT)
- Fibrinogen Level
- Thrombin Time (TT)
- Prothrombin Time / International Normalized Ratio (PT/INR) (Correct answer)
Correct answer: Prothrombin Time / International Normalized Ratio (PT/INR)
Warfarin is a vitamin K antagonist that inhibits the synthesis of clotting factors II, VII, IX, and X. The Prothrombin Time (PT) test evaluates the extrinsic and common coagulation pathways, which include these factors. The International Normalized Ratio (INR) standardizes the PT result, making it the primary test for monitoring warfarin therapy.
Question 4: Given the following patient data, calculate the Mean Corpuscular Hemoglobin (MCH): Hemoglobin: 15 g/dL RBC Count: 5.0 x 10^12/L Hematocrit: 45%
- 33.3 g/dL
- 90 fL
- 30 pg (Correct answer)
- 10 g/dL
Correct answer: 30 pg
The formula for MCH is (Hemoglobin x 10) / RBC Count (in millions/µL). The RBC count of 5.0 x 10^12/L is equivalent to 5.0 million/µL. Therefore, MCH = (15 x 10) / 5.0 = 30 pg.
Question 5: A patient presents with mucocutaneous bleeding. Laboratory findings include a normal platelet count, giant platelets on the peripheral smear, and impaired platelet aggregation with ristocetin. Aggregation with ADP, collagen, and epinephrine is normal. These findings are most consistent with which platelet disorder?
- Glanzmann Thrombasthenia
- von Willebrand Disease
- Bernard-Soulier Syndrome (Correct answer)
- Idiopathic Thrombocytopenic Purpura (ITP)
Correct answer: Bernard-Soulier Syndrome
Bernard-Soulier Syndrome is characterized by a defect in the GPIb/IX/V complex on the platelet surface, which is the receptor for von Willebrand factor. This leads to defective platelet adhesion. Key lab findings include thrombocytopenia (often mild), giant platelets, and a lack of aggregation with ristocetin, while aggregation to other agonists like ADP is normal.
Question 6: An elevated D-dimer test is most clinically significant for which of the following applications?
- Confirming a diagnosis of Deep Vein Thrombosis (DVT)
- Ruling out venous thromboembolism (VTE) in a low-probability patient (Correct answer)
- Monitoring heparin therapy effectiveness
- Diagnosing Hemophilia A
Correct answer: Ruling out venous thromboembolism (VTE) in a low-probability patient
The D-dimer test measures a specific fibrin degradation product. It has a high negative predictive value, meaning a normal result makes a venous thromboembolism (like DVT or pulmonary embolism) highly unlikely. However, it has low specificity, as many other conditions can cause an elevated level. Therefore, its primary clinical utility is to rule out VTE in patients with a low pretest probability.
Medical Laboratory Technician Hematology and Coagulation Questions and Answers
A patient is receiving unfractionated heparin therapy for deep vein thrombosis.
The clinical protocol requires maintaining the aPTT at 1.5 to 2.5 times the mean of the normal range.
The laboratory's normal aPTT range is 28-38 seconds.
Which of the following results is within the therapeutic range for this patient?