Welcome to Part 45 of our Free ASCP MLS Exam Practice Questions series. This section focuses on Coagulation Testing, one of the most important areas of hematology and clinical laboratory practice. Accurate assessment of the coagulation system is essential for diagnosing bleeding and thrombotic disorders, monitoring therapy, and guiding patient care.
🔹 Topics Covered in This Part
- Prothrombin Time (PT) and International Normalized Ratio (INR)
- Activated Partial Thromboplastin Time (aPTT)
- Mixing studies and interpretation of correction patterns
- Factor assays (quantitative and qualitative methods)
- Specialized coagulation studies (thrombin time, fibrinogen assay, D-dimer, lupus anticoagulant testing)
- Clinical applications: monitoring anticoagulant therapy (warfarin, heparin, DOACs)
60 MCQs (3641 – 3700):
📘 How to Use These Practice Questions
- This set tests your knowledge of principles, methods, and interpretation of coagulation tests.
- Numbering continues from the previous article — starting at Question 3641.
- Answer keys with explanations will follow at the end for effective review and exam readiness.
- The Prothrombin Time (PT) test is most sensitive to deficiencies in which coagulation pathway?
a) Intrinsic Pathway
b) Extrinsic Pathway
c) Common Pathway
d) Fibrinolytic Pathway - The Activated Partial Thromboplastin Time (aPTT) test is most sensitive to deficiencies in which coagulation pathway?
a) Intrinsic Pathway
b) Extrinsic Pathway
c) Common Pathway
d) Fibrinolytic Pathway - A patient on warfarin (Coumadin) therapy would be expected to have a prolonged:
a) Bleeding Time
b) Thrombin Time (TT)
c) Prothrombin Time (PT)
d) Activated Clotting Time (ACT) - Which of the following coagulation factors is Vitamin K dependent?
a) Factor V
b) Factor VIII
c) Factor XI
d) Factor II (Prothrombin) - The Thrombin Time (TT) test measures the final step of the coagulation cascade, which is:
a) The activation of Factor X
b) The conversion of prothrombin to thrombin
c) The conversion of fibrinogen to fibrin
d) The cross-linking of fibrin polymers - A prolonged Prothrombin Time (PT) and a normal Activated Partial Thromboplastin Time (aPTT) is most suggestive of a deficiency in which factor?
a) Factor VIII
b) Factor IX
c) Factor VII
d) Factor XI - A prolonged Activated Partial Thromboplastin Time (aPTT) that does not correct with mixing studies is most indicative of:
a) A specific factor deficiency
b) The presence of an inhibitor
c) Vitamin K deficiency
d) A problem with the sample collection - Hemophilia A is caused by a deficiency of which coagulation factor?
a) Factor VIII
b) Factor IX
c) Factor XI
d) Factor XII - The International Normalized Ratio (INR) was developed to:
a) Replace the Prothrombin Time test
b) Standardize PT results across different laboratories and reagents
c) Measure the activity of the intrinsic pathway
d) Assess platelet function - The test used to screen for the Lupus Anticoagulant (LA) is typically a(n):
a) Prolonged PT
b) Prolonged TT
c) Prolonged aPTT that does not correct with mixing
d) Shortened Bleeding Time - A patient with liver disease would most likely exhibit:
a) A prolonged PT and aPTT
b) A shortened PT and aPTT
c) A prolonged PT only
d) A prolonged aPTT only - Disseminated Intravascular Coagulation (DIC) is characterized by all of the following laboratory findings EXCEPT:
a) Prolonged PT and aPTT
b) Elevated fibrinogen levels
c) Decreased platelet count
d) Elevated D-dimer levels - The PFA-100 (Platelet Function Analyzer) is used to assess:
a) Specific coagulation factor levels
b) Primary hemostasis (platelet plug formation)
c) Fibrinolytic system activity
d) The presence of circulating anticoagulants - The mixing study is used to distinguish between:
a) Vitamin K deficiency and liver disease
b) Factor deficiency and inhibitor presence
c) Hemophilia A and Hemophilia B
d) DIC and primary fibrinolysis - Which of the following tests would be most sensitive to the presence of unfractionated heparin?
a) Prothrombin Time (PT)
b) Activated Partial Thromboplastin Time (aPTT)
c) Thrombin Time (TT)
d) Bleeding Time - A deficiency of Factor XIII is best detected by:
a) Prolonged PT
b) Prolonged aPTT
c) Clot solubility test in 5M urea
d) Prolonged Thrombin Time - The reptilase time is used to differentiate heparin effect from other causes of a prolonged thrombin time because reptilase:
a) Is inhibited by heparin
b) Is not inhibited by heparin
c) Measures fibrinogen levels directly
d) Activates Protein C - The D-dimer test is a measure of:
a) Platelet activation
b) Fibrinogen degradation
c) Cross-linked fibrin degradation
d) Thrombin generation - In a patient with a suspected bleeding disorder, a normal PT and aPTT would most likely rule out a deficiency in which of the following?
a) Factor VIII
b) Factor XIII
c) Vitamin K dependent factors
d) Factors in the intrinsic and extrinsic pathways - The primary role of Protein C and Protein S in the coagulation system is to:
a) Activate Factor V and Factor VIII
b) Act as cofactors for thrombin
c) Inactivate Factor Va and Factor VIIIa
d) Promote platelet aggregation - The test of choice for monitoring low molecular weight heparin (LMWH) therapy is:
a) Activated Partial Thromboplastin Time (aPTT)
b) Anti-Factor Xa assay
c) Prothrombin Time (PT)
d) Thrombin Time (TT) - A patient with a prolonged aPTT has a normal PT. A mixing study with normal plasma corrects the aPTT. This indicates:
a) The presence of a Lupus Anticoagulant
b) A specific factor deficiency
c) The presence of a Factor VIII inhibitor
d) Heparin contamination - Which of the following conditions is associated with a prolonged bleeding time but normal platelet count?
a) Immune Thrombocytopenic Purpura (ITP)
b) Von Willebrand Disease (vWD)
c) Hemophilia A
d) Vitamin K deficiency - The principle of the clot-based PT test involves the addition of which reagent to citrated plasma?
a) Kaolin and phospholipid
b) Tissue factor (thromboplastin) and calcium
c) Thrombin and calcium
d) Russell’s viper venom and calcium - The most common cause of an error in coagulation testing is:
a) Instrument malfunction
b) Improper sample collection (e.g., underfilled tube)
c) Reagent degradation
d) Incorrect incubation time - The Activated Protein C Resistance (APCR) test is most commonly associated with a mutation in:
a) Prothrombin
b) Factor V (Factor V Leiden)
c) MTHFR
d) Protein S - A falsely prolonged PT and aPTT in a patient with no bleeding symptoms could be caused by:
a) Hemophilia A
b) A high hematocrit (>55%) leading to excess citrate
c) Liver failure
d) Disseminated Intravascular Coagulation (DIC) - The test used to confirm the presence of Heparin-Induced Thrombocytopenia (HIT) antibodies is:
a) Serotonin release assay
b) Anti-Factor Xa assay
c) D-dimer
d) Fibrinogen level - In the coagulation cascade, calcium ions are required for:
a) The activation of Factor XII
b) The binding of vitamin K to its dependent factors
c) The binding of coagulation factors to phospholipid surfaces
d) The inhibition of Protein C - A patient with a family history of thrombosis is found to have decreased levels of free Protein S antigen. This is most consistent with:
a) Factor V Leiden mutation
b) Protein S deficiency
c) Antithrombin III deficiency
d) Prothrombin G20210A mutation - Prothrombin time (PT) primarily evaluates which pathway?
a) Intrinsic
b) Extrinsic and common
c) Fibrinolytic
d) Platelet adhesion - Activated partial thromboplastin time (aPTT) primarily evaluates which pathway?
a) Intrinsic and common
b) Extrinsic only
c) Platelet function
d) Fibrinolysis - Which reagent is required in PT testing?
a) Calcium chloride and tissue factor (thromboplastin)
b) Platelet-rich plasma
c) Kaolin and phospholipid
d) Collagen - Which reagent is required in aPTT testing?
a) Tissue factor
b) Kaolin, phospholipid, and calcium chloride
c) Platelet-rich plasma only
d) D-dimer reagent\ - Which condition typically prolongs PT but not aPTT?
a) Factor VII deficiency
b) Hemophilia A
c) Hemophilia B
d) Factor XI deficiency - Which condition prolongs aPTT but not PT?
a) Factor VIII deficiency
b) Factor VII deficiency
c) Vitamin K deficiency
d) Warfarin therapy - Which condition prolongs both PT and aPTT?
a) Hemophilia A
b) Liver disease
c) Factor VII deficiency
d) von Willebrand disease - The INR (International Normalized Ratio) is used to monitor therapy with:
a) Heparin
b) Warfarin
c) Aspirin
d) Direct Xa inhibitors - Heparin therapy is best monitored using:
a) PT/INR
b) aPTT
c) D-dimer
d) Platelet count - The thrombin time (TT) evaluates:
a) Conversion of prothrombin to thrombin
b) Conversion of fibrinogen to fibrin
c) Platelet aggregation
d) Factor XIII activity - A prolonged thrombin time with normal reptilase time suggests:
a) Heparin contamination
b) Dysfibrinogenemia
c) Factor VII deficiency
d) Vitamin K deficiency - The mixing study helps distinguish between:
a) Platelet vs coagulation disorders
b) Factor deficiency vs inhibitor
c) Primary vs secondary hemostasis
d) Intrinsic vs extrinsic pathway - If a prolonged aPTT corrects after mixing study, the cause is most likely:
a) Lupus anticoagulant
b) Specific factor inhibitor
c) Factor deficiency
d) Vitamin K deficiency - If a prolonged aPTT does not correct after mixing study, the cause is most likely:
a) Factor deficiency
b) Lupus anticoagulant or inhibitor
c) Vitamin K deficiency
d) Platelet dysfunction - Factor VIII assays are typically performed using:
a) PT method
b) aPTT-based clotting assay
c) Platelet aggregation test
d) Chromogenic anti-Xa assay - Factor IX assays are important for diagnosis of:
a) Hemophilia A
b) Hemophilia B
c) von Willebrand disease
d) Factor VII deficiency - Reptilase time differs from thrombin time because:
a) It is not affected by heparin
b) It is faster than thrombin time
c) It uses platelet factor 3
d) It requires calcium - Which factor deficiency leads to prolonged clotting but no bleeding symptoms?
a) Factor VIII
b) Factor IX
c) Factor XII
d) Factor VII - Which assay is used to detect lupus anticoagulant?
a) Platelet function test
b) Dilute Russell viper venom test (dRVVT)
c) PT/INR
d) Thrombin time - Which coagulation factor is most sensitive to vitamin K deficiency?
a) Factor IX
b) Factor VII
c) Factor X
d) Factor II - In DIC, laboratory findings usually include:
a) Normal PT, aPTT, and fibrinogen
b) Prolonged PT and aPTT, low fibrinogen, high D-dimer
c) Isolated prolonged PT
d) Isolated prolonged aPTT - Which coagulation test uses optical density to measure clot formation?
a) Mechanical clot detection
b) Photo-optical method
c) Chromogenic substrate assay
d) Flow cytometry - Chromogenic factor assays measure:
a) Cell granularity
b) Enzyme activity of specific coagulation factors
c) Platelet aggregation
d) Hemoglobin electrophoresis - The Bethesda assay is used to measure:
a) Platelet antibodies
b) Factor VIII inhibitors
c) Heparin concentration
d) Fibrinogen level - The anti-Xa assay is commonly used to monitor therapy with:
a) Warfarin
b) Unfractionated and low-molecular-weight heparin
c) Aspirin
d) Vitamin K - Which test evaluates fibrinolysis by measuring plasminogen activity?
a) Thrombin time
b) Euglobulin clot lysis time
c) Mixing study
d) dRVVT - Which factor deficiency causes both prolonged PT and aPTT but normal thrombin time?
a) Factor V
b) Factor VIII
c) Factor XII
d) Factor VII - Which laboratory abnormality is most consistent with vitamin K deficiency?
a) Prolonged PT, prolonged aPTT, low factor VII
b) Normal PT, prolonged aPTT
c) Prolonged thrombin time only
d) Isolated prolonged reptilase time - Which condition may interfere with PT/INR monitoring due to prolonged baseline clotting?
a) Lupus anticoagulant
b) Hemophilia A
c) vWD
d) Aspirin therapy - Which coagulation test is most sensitive to fibrinogen deficiency?
a) PT
b) aPTT
c) Thrombin time
d) dRVVT
📌 How to Use This Practice Set
- Answer each question before checking the key.
- Focus on why the correct answer is right and the others are wrong.
- Use this set as timed practice to simulate the real exam environment.
Answer Key
Answer Key:
- b) Extrinsic Pathway
- a) Intrinsic Pathway
- c) Prothrombin Time (PT)
- d) Factor II (Prothrombin)
- c) The conversion of fibrinogen to fibrin
- c) Factor VII
- b) The presence of an inhibitor
- a) Factor VIII
- b) Standardize PT results across different laboratories and reagents
- c) Prolonged aPTT that does not correct with mixing
- a) A prolonged PT and aPTT
- b) Elevated fibrinogen levels
- b) Primary hemostasis (platelet plug formation)
- b) Factor deficiency and inhibitor presence
- b) Activated Partial Thromboplastin Time (aPTT)
- c) Clot solubility test in 5M urea
- b) Is not inhibited by heparin
- c) Cross-linked fibrin degradation
- d) Factors in the intrinsic and extrinsic pathways
- c) Inactivate Factor Va and Factor VIIIa
- b) Anti-Factor Xa assay
- b) A specific factor deficiency
- b) Von Willebrand Disease (vWD)
- b) Tissue factor (thromboplastin) and calcium
- b) Improper sample collection (e.g., underfilled tube)
- b) Factor V (Factor V Leiden)
- b) A high hematocrit (>55%) leading to excess citrate
- a) Serotonin release assay
- c) The binding of coagulation factors to phospholipid surfaces
- b) Protein S deficiency
- b) Extrinsic and common
- a) Intrinsic and common
- a) Calcium chloride and tissue factor (thromboplastin)
- b) Kaolin, phospholipid, and calcium chloride
- a) Factor VII deficiency
- a) Factor VIII deficiency
- b) Liver disease
- b) Warfarin
- b) aPTT
- b) Conversion of fibrinogen to fibrin
- a) Heparin contamination
- b) Factor deficiency vs inhibitor
- c) Factor deficiency
- b) Lupus anticoagulant or inhibitor
- b) aPTT-based clotting assay
- b) Hemophilia B
- a) It is not affected by heparin
- c) Factor XII
- b) Dilute Russell viper venom test (dRVVT)
- b) Factor VII
- b) Prolonged PT and aPTT, low fibrinogen, high D-dimer
- b) Photo-optical method
- b) Enzyme activity of specific coagulation factors
- b) Factor VIII inhibitors
- b) Unfractionated and low-molecular-weight heparin
- b) Euglobulin clot lysis time
- a) Factor V
- a) Prolonged PT, prolonged aPTT, low factor VII
- a) Lupus anticoagulant
- c) Thrombin time
Top 8 Medical Laboratory Scientist (MLS) Exams:
Top 8 Medical Laboratory Scientist (MLS) Exams that are recognized globally and can help professionals validate their credentials and enhance their career opportunities:
1. ASCP – American Society for Clinical Pathology (USA)
- Exam Name: MLS(ASCP)
- Eligibility: Bachelor’s degree with clinical laboratory experience.
- Global Recognition: High
- Purpose: Certifies Medical Laboratory Scientists in the United States and internationally.
2. AMT – American Medical Technologists (USA)
- Exam Name: MLT(AMT) or MT(AMT)
- Eligibility: Academic and/or work experience in medical laboratory technology.
- Global Recognition: Moderate
- Purpose: Credentialing for medical technologists and technicians.
3. AIMS – Australian Institute of Medical and Clinical Scientists
- Exam Name: AIMS Certification Exam
- Eligibility: Assessment of qualifications and work experience.
- Recognition: Required for practice in Australia.
- Purpose: Certification and registration in Australia.
4. CSMLS – Canadian Society for Medical Laboratory Science
- Exam Name: CSMLS General or Subject-specific Exams
- Eligibility: Graduation from a CSMLS-accredited program or equivalent.
- Recognition: Canada
- Purpose: Entry-to-practice certification in Canada.
5. IBMS – Institute of Biomedical Science (UK)
- Exam Name: Registration and Specialist Portfolio Assessment
- Eligibility: Accredited degree and lab experience.
- Recognition: UK and some Commonwealth countries.
- Purpose: Biomedical Scientist registration with the HCPC (UK).
6. HAAD / DOH – Department of Health, Abu Dhabi (UAE)
- Exam Name: DOH/HAAD License Exam
- Eligibility: Degree in medical laboratory science and experience.
- Recognition: UAE (Abu Dhabi)
- Purpose: Licensure for medical laboratory practice in Abu Dhabi.
7. DHA – Dubai Health Authority (UAE)
- Exam Name: DHA License Exam for Medical Laboratory Technologists
- Eligibility: Relevant degree and experience.
- Recognition: Dubai, UAE
- Purpose: Professional license for clinical laboratory practice in Dubai.
8. MOH – Ministry of Health (Gulf Countries like UAE, Saudi Arabia, Kuwait)
- Exam Name: MOH License Exam
- Eligibility: BSc/Diploma in Medical Laboratory + experience.
- Recognition: Varies by country.
- Purpose: Required for practicing in public and private sector labs.
Tags:
#ASCPMLS #MLSexam #LabTech #MedicalLaboratory #BOCexam #FreePracticeQuestions #QualityControl #LaboratorySafety
