A patient's prolonged APTT corrects fully when mixed 1:1 with normal plasma and tested at once, but becomes prolonged again after the mix is incubated for 2 hours at 37°C. This pattern indicates:

An acquired factor VIII inhibitor

An inherited factor IX deficiency

Heparin contamination of the sample

A 58-year-old man in the ICU on broad-spectrum antibiotics, with poor oral intake for two weeks, has: PT 26 s (control 13 s), APTT 44 s (26-36 s), thrombin time normal, fibrinogen 330 mg/dL, platelets 2.5 lakhs/µL, factor V 92% and factor VII 15%. The most likely cause is:

Disseminated intravascular coagulation

A patient with polycythaemia (PCV 68%) has blood drawn into a standard 3.2% citrate tube. The PT and APTT will be:

Falsely prolonged, from excess citrate in the plasma

Falsely shortened, from activation of platelets

Accurate, as the citrate ratio stays fixed

Falsely prolonged, from dilution of the factors

Haemostasis and coagulation tests

35 Kerala MSc MLT Entrance practice questions on Haemostasis and coagulation tests, part of Haematology and Blood Banking. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
A patient's prolonged APTT corrects fully when mixed 1:1 with normal plasma and tested at once, but becomes prolonged again after the mix is incubated for 2 hours at 37°C. This pattern indicates:
1. AA lupus anticoagulant
2. BAn acquired factor VIII inhibitor
3. CAn inherited factor IX deficiency
4. DHeparin contamination of the sample
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Answer: B · An acquired factor VIII inhibitor
A factor deficiency corrects both at once and after incubation, because normal plasma supplies at least 50% of every factor. Acquired factor VIII antibodies are typically time- and temperature-dependent, so the immediate mix may correct while the incubated mix lengthens as the antibody slowly inactivates factor VIII (an incubated normal control is run alongside). Lupus anticoagulant usually acts at once, so the immediate mix fails to correct. Heparin also prevents immediate correction, and a prolonged thrombin time points to it.
- A: Lupus anticoagulant usually prevents correction even in the immediate mix.
- C: A deficiency corrects both immediately and after incubation.
- D: Heparin prevents correction at once and prolongs the thrombin time.
Question 2 · Hard
A 58-year-old man in the ICU on broad-spectrum antibiotics, with poor oral intake for two weeks, has: PT 26 s (control 13 s), APTT 44 s (26-36 s), thrombin time normal, fibrinogen 330 mg/dL, platelets 2.5 lakhs/µL, factor V 92% and factor VII 15%. The most likely cause is:
1. AVitamin K deficiency
2. BDisseminated intravascular coagulation
3. CHeparin contamination
4. DAcute liver failure
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Answer: A · Vitamin K deficiency
A long PT with a milder rise in APTT, and normal fibrinogen, thrombin time and platelets, points to a fall in the vitamin K-dependent factors II, VII, IX and X. Factor VII has the shortest half-life, so it falls first and the PT lengthens before the APTT. Factor V is not vitamin K dependent, so a normal factor V separates vitamin K deficiency from liver failure, in which factor V also falls. Antibiotics that kill gut flora plus poor diet are a common ICU cause, and the PT improves within 12-24 hours of parenteral vitamin K.
- B: DIC consumes fibrinogen and platelets and raises D-dimer.
- C: Heparin prolongs the thrombin time, which here is normal.
- D: Liver failure lowers factor V as well as the vitamin K-dependent factors.
Question 3 · Easy
Tissue factor starts coagulation in vivo by forming a complex with which factor?
1. AActivated factor XII
2. BActivated factor VII
3. CThrombin
4. DActivated factor IX
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Answer: B · Activated factor VII
Injury exposes tissue factor on subendothelial cells; it binds factor VII and activates it, and the TF-VIIa complex then activates factors X and IX. The small burst of thrombin produced amplifies coagulation by activating factors V, VIII and XI and platelets. Factor XII deficiency prolongs the APTT but causes no bleeding, which shows that contact activation is not needed in vivo. The PT, which uses tissue factor as thromboplastin, tests this pathway in vitro.
- A: Factor XII starts the contact pathway in vitro and is not needed for haemostasis.
- C: Thrombin is formed downstream and amplifies the process.
- D: Factor IXa is produced by TF-VIIa and acts later with factor VIIIa.
Question 4 · Medium
A patient with polycythaemia (PCV 68%) has blood drawn into a standard 3.2% citrate tube. The PT and APTT will be:
1. AFalsely shortened, from activation of platelets
2. BFalsely prolonged, from excess citrate in the plasma
3. CAccurate, as the citrate ratio stays fixed
4. DFalsely prolonged, from dilution of the factors
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Answer: B · Falsely prolonged, from excess citrate in the plasma
The 9:1 ratio assumes a normal PCV. With a PCV of 68% there is much less plasma, so the citrate is excessive for that plasma; when calcium is added in the test, some is still bound by the extra citrate and clotting is delayed. The citrate volume should be reduced when the PCV is above 55%, using C = 0.00185 x (100 - PCV) x blood volume (mL). Polycythaemia does not dilute the factors; the error comes from the anticoagulant.
- A: A high PCV does not activate platelets; that follows poor collection technique.
- C: The citrate-to-plasma ratio rises as the PCV rises.
- D: The factors are not diluted; the plasma simply holds too much citrate.
Question 5 · Hard
A patient on warfarin has a PT of 26 s. The laboratory's mean normal PT is 13 s and the thromboplastin ISI is 1.5. What is the INR?
1. A1.6
2. B2.0
3. C3.0
4. D2.8
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Answer: D · 2.8
INR = (patient PT / mean normal PT) raised to the power ISI. The PT ratio is 26 / 13 = 2.0, and 2.0 to the power 1.5 is 2.83, reported as 2.8, within the usual warfarin target of 2.0-3.0. Multiplying the ratio by the ISI gives 3.0, and ignoring the ISI gives 2.0; both are common errors. The ISI expresses the thromboplastin's sensitivity relative to the WHO international reference, which has an ISI of 1.0.
- A: 1.6 comes from using 1/ISI as the power.
- B: 2.0 is the PT ratio, before the ISI is applied.
- C: 3.0 comes from multiplying the ratio by the ISI instead of using it as a power.
Question 6 · Easy
The Clauss method measures plasma fibrinogen from the:
1. AOptical clot curve of the prothrombin time
2. BClotting time of diluted plasma with excess thrombin
3. CWeight of the clot formed after recalcification
4. DTurbidity of plasma heated to 56°C
Answer and explanation in LearnFree account
Question 7 · Medium
Platelet aggregation shows normal responses to ADP, collagen and adrenaline but no response to ristocetin, and adding normal plasma does not correct it. The film shows giant platelets. What is the most likely diagnosis?
1. ABernard-Soulier syndrome
2. BVon Willebrand disease
3. CGlanzmann thrombasthenia
4. DAspirin ingestion
Answer and explanation in LearnFree account
Question 8 · Hard
A 19-year-old woman has heavy periods and frequent nosebleeds; her mother has the same problem. Platelet count 2.6 lakhs/µL, bleeding time prolonged, PT normal and APTT slightly prolonged. Which set of tests should come next?
1. AVWF antigen, VWF activity and factor VIII
2. BClot solubility in 5 M urea
3. CFactor IX assay and an inhibitor screen
4. DFibrinogen and a thrombin time
Answer and explanation in LearnFree account
Question 9 · Medium
Clot retraction is poor although the platelet count is normal. Which disorder fits?
1. AVon Willebrand disease
2. BHaemophilia A
3. CFactor XIII deficiency
4. DGlanzmann thrombasthenia
Answer and explanation in LearnFree account
Question 10 · Hard
Before dental surgery, a 60-year-old man has a bleeding time of 11 min (Ivy, 2-7 min), platelets 2.4 lakhs/µL, normal PT and APTT. Aggregation: absent with arachidonic acid, primary wave only with ADP and adrenaline, reduced with collagen, normal with ristocetin. The most likely cause is:
1. ARecent aspirin intake
2. BBernard-Soulier syndrome
3. CGlanzmann thrombasthenia
4. DVon Willebrand disease
Answer and explanation in LearnFree account
Question 11 · Hard
Before a hernia repair, a 40-year-old man with no bleeding history, even after a tooth extraction, has an APTT of 98 s (26-36 s) and a normal PT. The APTT corrects with a 1:1 mix, at once and after 2 hours' incubation. Factors VIII, IX and XI are normal; factor XII is under 1%. What should the report convey?
1. AHaemophilia; factor cover is needed
2. BLupus anticoagulant; give anticoagulant cover
3. CNo bleeding risk; surgery can go ahead
4. DInhibitor present; surgery must be delayed
Answer and explanation in LearnFree account
Question 12 · Easy
The plasma fibrinogen concentration of a healthy adult is about:
1. A20-40 mg/dL
2. B6-8 g/dL
3. C2-4 g/dL
4. D200-400 mg/dL
Answer and explanation in LearnFree account
Question 13 · Hard
A 7-year-old boy has had two knee bleeds after minor falls but no spontaneous bleeds. APTT 58 s (26-36 s), normal PT, factor VIII 3% and factor IX 95%. How is his disease classified?
1. AModerate haemophilia B
2. BMild haemophilia A
3. CSevere haemophilia A
4. DModerate haemophilia A
Answer and explanation in LearnFree account
Question 14 · Medium
A citrated sample for APTT was left at room temperature overnight before testing, and the APTT is prolonged. Loss of which factors best explains this?
1. AFactors VII and IX
2. BFactors V and VIII
3. CFactors II and X
4. DFactors XI and XII
Answer and explanation in LearnFree account
Question 15 · Easy
During fibrinolysis, which enzyme digests fibrin into degradation products?
1. AKallikrein
2. BFactor XIIIa
3. CPlasmin
4. DThrombin
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Question 16 · Medium
A man with haemophilia A and a woman with normal genes have children. How many of their daughters will be carriers?
1. AAll of them
2. BOne in four
3. CHalf of them
4. DNone of them
Answer and explanation in LearnFree account
Question 17 · Medium
Plasma for routine PT and APTT should be platelet-poor. By CLSI guidance, its platelet count after centrifugation should be below:
1. A1,00,000/µL
2. B50,000/µL
3. C10,000/µL
4. D1,50,000/µL
Answer and explanation in LearnFree account
Question 18 · Medium
Low-molecular-weight heparin is monitored, when needed, by an anti-factor Xa assay rather than the APTT. Why?
1. AIt acts without antithrombin, so the APTT cannot detect it
2. BIt binds the APTT phospholipid, so the APTT is always shortened
3. CIt lowers the vitamin K-dependent factors, prolonging only the PT
4. DIt inhibits Xa far more than thrombin, so the APTT barely changes
Answer and explanation in LearnFree account
Question 19 · Easy
How many parts of blood are added to one part of 0.109 M sodium citrate in a tube for clotting tests?
1. AOne
2. BNine
3. CNineteen
4. DFour
Answer and explanation in LearnFree account
Question 20 · Medium
In the Ivy method of bleeding time, the sphygmomanometer cuff on the upper arm is kept at:
1. A80 mmHg
2. B120 mmHg
3. C40 mmHg
4. D20 mmHg
Answer and explanation in LearnFree account
Question 21 · Medium
A patient has a prolonged prothrombin time, but the APTT, thrombin time and platelet count are normal. The deficiency most likely involves:
1. AFibrinogen
2. BFactor VII
3. CFactor VIII
4. DFactor X
Answer and explanation in LearnFree account
Question 22 · Medium
The PT, APTT and thrombin time are all prolonged, and heparin has been excluded. The defect most likely lies at which step?
1. AActivation of factor X by factor VIIa
2. BConversion of fibrinogen to fibrin
3. CActivation of factor IX by factor XIa
4. DActivation of factor XII by contact
Answer and explanation in LearnFree account
Question 23 · Medium
A raised plasma D-dimer, unlike a raised level of total fibrinogen degradation products, specifically shows that:
1. AThrombin generation has been blocked
2. BPlasmin has digested intact fibrinogen
3. CPlasmin has digested cross-linked fibrin
4. DPlatelets have failed to aggregate
Answer and explanation in LearnFree account
Question 24 · Hard
An ICU sample drawn through a central line gives APTT over 150 s, thrombin time over 100 s (control 15 s), PT 16 s (control 13 s) and fibrinogen 320 mg/dL. A reptilase time is normal. The patient is not prescribed heparin and is not bleeding. What is the most likely explanation?
1. ADisseminated intravascular coagulation
2. BHeparin from the line flush contaminated the sample
3. CSevere congenital deficiency of fibrinogen
4. DA lupus anticoagulant in the patient
Answer and explanation in LearnFree account
Question 25 · Easy
In the Hess (tourniquet) test, a blood pressure cuff is inflated on the arm and the petechiae below it are counted. The test assesses:
1. AThe rate of fibrinolysis
2. BThe intrinsic pathway of coagulation
3. CCapillary fragility and platelet function
4. DThe plasma fibrinogen level
Answer and explanation in LearnFree account

10 more Haemostasis and coagulation tests questions

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Haemostasis and coagulation tests

A patient's prolonged APTT corrects fully when mixed 1:1 with normal plasma and tested at once, but becomes prolonged again after the mix is incubated for 2 hours at 37°C. This pattern indicates:

A 58-year-old man in the ICU on broad-spectrum antibiotics, with poor oral intake for two weeks, has: PT 26 s (control 13 s), APTT 44 s (26-36 s), thrombin time normal, fibrinogen 330 mg/dL, platelets 2.5 lakhs/µL, factor V 92% and factor VII 15%. The most likely cause is:

Tissue factor starts coagulation in vivo by forming a complex with which factor?

A patient with polycythaemia (PCV 68%) has blood drawn into a standard 3.2% citrate tube. The PT and APTT will be:

A patient on warfarin has a PT of 26 s. The laboratory's mean normal PT is 13 s and the thromboplastin ISI is 1.5. What is the INR?

The Clauss method measures plasma fibrinogen from the:

Platelet aggregation shows normal responses to ADP, collagen and adrenaline but no response to ristocetin, and adding normal plasma does not correct it. The film shows giant platelets. What is the most likely diagnosis?

A 19-year-old woman has heavy periods and frequent nosebleeds; her mother has the same problem. Platelet count 2.6 lakhs/µL, bleeding time prolonged, PT normal and APTT slightly prolonged. Which set of tests should come next?

Clot retraction is poor although the platelet count is normal. Which disorder fits?

Before dental surgery, a 60-year-old man has a bleeding time of 11 min (Ivy, 2-7 min), platelets 2.4 lakhs/µL, normal PT and APTT. Aggregation: absent with arachidonic acid, primary wave only with ADP and adrenaline, reduced with collagen, normal with ristocetin. The most likely cause is:

The plasma fibrinogen concentration of a healthy adult is about:

A 7-year-old boy has had two knee bleeds after minor falls but no spontaneous bleeds. APTT 58 s (26-36 s), normal PT, factor VIII 3% and factor IX 95%. How is his disease classified?

A citrated sample for APTT was left at room temperature overnight before testing, and the APTT is prolonged. Loss of which factors best explains this?

During fibrinolysis, which enzyme digests fibrin into degradation products?

A man with haemophilia A and a woman with normal genes have children. How many of their daughters will be carriers?

Plasma for routine PT and APTT should be platelet-poor. By CLSI guidance, its platelet count after centrifugation should be below:

Low-molecular-weight heparin is monitored, when needed, by an anti-factor Xa assay rather than the APTT. Why?

How many parts of blood are added to one part of 0.109 M sodium citrate in a tube for clotting tests?

In the Ivy method of bleeding time, the sphygmomanometer cuff on the upper arm is kept at:

A patient has a prolonged prothrombin time, but the APTT, thrombin time and platelet count are normal. The deficiency most likely involves:

The PT, APTT and thrombin time are all prolonged, and heparin has been excluded. The defect most likely lies at which step?

A raised plasma D-dimer, unlike a raised level of total fibrinogen degradation products, specifically shows that:

An ICU sample drawn through a central line gives APTT over 150 s, thrombin time over 100 s (control 15 s), PT 16 s (control 13 s) and fibrinogen 320 mg/dL. A reptilase time is normal. The patient is not prescribed heparin and is not bleeding. What is the most likely explanation?

In the Hess (tourniquet) test, a blood pressure cuff is inflated on the arm and the petechiae below it are counted. The test assesses: