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Data Interpretation > Coagulation > Flashcards

Coagulation Flashcards

1
Q

What are the 2 main components required to achieve haemostasis (clotting)

A

Functioning platelets
Functioning coagulation cascade

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2
Q

What is meant by primary and secondary haemostasis

A

Damage to blood vessels exposes collagen to platelets which then aggregate to form a platelet clot. This is primary haemostasis

Damage to blood vessels also activates the coagulation cascade where the end product of the common pathway being Fibrin. This is secondary haemostasis

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3
Q

Give 3 examples of mucocutaneous bleeds

Are these types of bleeds associated with platelet disorders or coagulation disorders?

A

Epistaxis
Gingival bleed
Menorrhagia
ecchymosis/bruising

Platelet disorder or extrinsic pathway (e.g Alexander’s)

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4
Q

A patient presenting with haemarthrosis of the knee after a fall with a history of muscle haematomas is consistent with platelet disorders or coagulation disorders?

A

Coagulation disorders/intrinsic pathway

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5
Q

When taking a history regarding coagulation what is important to elicit?

A

Type: Mucocutaneous (platelet disorder OR EXTRINSIC PATHWAY) vs Haemarthrosis/muscle haematoma (coagulation disorder)
Severity: Anaemic? Required transfusions before?
Age of onset
Family hx of inherited disorders such as Factor V Liden, Factor VII (alexander’s disease), Haemophilia, menorrhagia
Drugs: DOAC, Heparin, Warfarin, Aspirin

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6
Q

What test will you order for a suspected deficiency in the intrinsic pathway?

What factors are included in the intrinsic pathway

A

PTT/aPTT

TENET: Twelve, eleven, nine, eight, ten (common)

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7
Q

What test will you order for a suspected deficiency in the extrinsic pathway?

What factors are included in the extrinsic pathway

A

PT

7 + tissue factor activating 10 (common)

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8
Q

Where are clotting factors produced?

A

Liver

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9
Q

What factors are included in the common pathway?

A

X, V, I, II

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10
Q

What are factors I and II called?

A

Factor I = fibrinogen
Factor II = Prothrombin

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11
Q

Go over the common pathway of the coagulation cascade

A

10 requires cofactor V to activate it into 10a which then activates Factor II or Prothrombin into Thrombin which then activates Factor I or fibrinogen into Fibrin which is the final product

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12
Q

A 51 year old patient is transferred to your haematology clinic with a known history of factor VII deficiency (Alexander’s Disease).

What blood test would you like to send?
What result will you expect

A

7 is part of the extrinsic pathway => PT showing a prolonged PT time (PTT time not affected)

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13
Q

You would like to order a coagulation screen to investigate unexplained bleeding but your examiner tells you that these tests are typically ordered separately. What are these separate tests theyre referring to? (6)

A

PT- prothrombin time
Thrombin time
aPTT - activated partial thromboplastin time
Fibrinogen
D-dimers
Bleeding time
INR (but only if warfarin is involved)

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14
Q

What is Thrombin time?

A

This measures the final step of coagulation which is the conversion from fibrinogen to fibrin (not prothrombin to thrombin)

Note: This test is not routinely used in initial screening

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15
Q

What drug primarily affects PT and what drug primarily affects aPTT

A

PT: Warfarin (Vitamin K antagonist and vitamin K primarily affects the extrinsic pathway)
aPTT: Heparin

FYI: DOACs are variable

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16
Q

A 35 year old patient with a metallic aortic valve presents to your clinic. Which coagulation study will be used to monitor his warfarin therapy?

A

INR

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17
Q

What is INR and what is the target range in:
Normal individual not on warfarin:
On warfarin for A.fib:
On warfarin for prosthetic valves:

A

INR is a standardized parameter only used to monitor warfarin and hence should only be used when discussing management on warfarin. It is derived from the patient’s PT and calculated as a ratio to a control PT using a formula

Normal individual not on warfarin: 1
On warfarin for A.fib: 2-3
On warfarin for prosthetic valves: 2.5-3.5/3-4

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18
Q

Give 5 indications for ordering a PT and 5 indications for ordering aPTT

A

PT: Suspected abnormalities in extrinsic pathway and to monitor warfarin therapy
aPTT: Suspected abnormalities in the intrinsic pathway and to monitor heparin therapy

Both: To investigate unexplained bleeding, Assess synthetic function of the liver, and the diagnosis of DIC

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19
Q

Give 5 causes of prolonged PT with normal aPTT

A

Factor VII deficiency (Alexander’s disease)
Mild vit.K deficiency
Mild liver disease
DIC
Warfarin

20
Q

Give 3 causes of prolonged aPTT but normal PT

A

Factors TENET deficiency
Von Willebrand disease
Heparin

21
Q

Briefly explain why Von Willebrand disease would only prolong aPTT but not PT

A

VW disease is a deficiency of VWF which serves as a carrier protein for factor VIII => intrinsic pathway (Part of TENET)

22
Q

Give 5 causes of prolonged PT AND aPTT

A

Collagen disorders: Marfan and Ehler danlos
Factor V Leiden
Severe vitamin K deficiency
Liver disease
DIC
Supratherapeutic doses of any anticoagulant (incluiding heparin and warfarin)

23
Q

What is the effect of antiplatelets on PT and aPTT

A

No effect

24
Q

How do collagen disorders affect PT and aPTT

A

Extend both as they are defined by abnormal collagen production => platelets wont aggregate as part of primary haemostasis requiring exposure of collagen to platelets.

25
Q

Haemophilia A is a deficiency in what clotting factor? How about haemophilia B?
Will they prolong PT, aPTT or both?

A

A = factor VIII
B = Factor IX
=> both are part of the intrinsic pathway => prolong aPTT

26
Q

A 4 year old child presents to your clinic with
a history of easy bruising and profound
bleeding after minor trauma. His mother
reports that her father (maternal grandfather)
died of heavy blood loss after a minor trauma. The child is diagnosed with Factor VIII deficiency (haemophilia A). Which coagulation test is most likely to be abnormal

A

aPTT

27
Q

A 20 year old man presents to your clinic. His mother had a diagnosis of Factor V Leiden deficiency. He reports that he suffers from easy bruising, but
has never had a major bleeding episode. He has never had a surgery, involved in a trauma or been to the dentist.

Which coagulation test(s) will you order?
Which coagulation test(s) are likely to be abnormal

A

factor V is part of the common pathway => both PT and aPTT are likely to be prolonged

28
Q

What is meant by a mixing study? Explain its use

A

A mixing study is used to determine if the patient has a clotting factor deficiency or if there is an “inhibitor” preventing clotting. It is conducted by mixing the patient’s plasma 50:50 with normal plasma

If there is a substantial increase in clotting => it is a clotting factor deficiency
If there is no substantial change => inhibitor preventing clotting even in the normal plasma

29
Q

Briefly explain what DIC is including:
Abbreviation
Causes
Pathogenesis
Treatment

A

Disseminated intravascular coagulation
Typically secondary to sepsis, burns, severe allergy, and malignancy. This causes clot formation in blood vessels leading to multiorgan failure. Due to the widespread nature of DIC, this consumes clotting factors most notably fibrinogen. Treatment is based on the identification and treatment of the underlying cause as well!! as transfusion of blood products by haematologists due to the risk of further clotting when these factors are replaced.

30
Q

In DIC what are the expected findings of each:
Platelets:
Fibrinogen:
D-dimer:

A

Platelets: low
Fibrinogen: low
D-dimer: high

31
Q

Your colleague orders the most hated test in the hospital, D-dimer. They tell you they hate it because it can be positive for multiple different reasons so then we would have to investigate as per guidelines. It is good at excluding PE/DVT though.

What is a D-Dimer?

When is it raised? Give 3/4

A

D-Dimer is one of the major fibrin degradation products which is produced during clot degeneration and hence the breakdown of fibrin.

It is raised in
1) Acute venous thromboembolism (PE/DVT)
2) DIC (low platelets and fibrinogen, high D-dimer)
3) Inflammation (infection, malignancy)
4) Hyperfibrinolysis (rare)

32
Q

Where is calf swelling measured in a case of DVT?

A

10cm below tibial tuberosity

33
Q

A 34 year old woman presents to the emergency department with a mildly swollen left lower limb. You calculate her Well’s Score as 6.

What are the components of the Well’s score used in this case? (including what to do based on results)

What are the components of the other Well’s score?

What are your next steps?

A

DVT Well’s score:
1) Active Cancer (treatment of Palliation within 6 months)
2) Bedridden >3 days or major surgery within 12 weeks
3) Calf swelling >3cm from other side (10cm below tibial tuberosity)
4) Entire Leg Swollen
5) Collateral (non-vericose) superficial veins present
6) Localized tenderness along deep venous system
7) Pitting oedema confined to symptomatic leg
8) Paralysis, paresis, or recent plaster immobilization of symptomatic leg
9) Previously documented DVT
10) Alternative diagnosis equally or more likely than DVT (-2)
0 or 1 => D-dimer to exclude. If +ve arrange Doppler US within 4hrs
2+ => Doppler US within 4 hours +/- D-dimer + Must arrange empiric anticoagulation (This case)

PE Well’s score:
1) Signs and symptoms of DVT (3)
2) Alternative diagnosis less likely (3)
3) HR >100 (1.5)
4) Immobilization >3 days or recent surgery within 4 weeks (1.5)
5) Previous PE/DVT (1.5)
6) Haemoptysis (1)
7) Active cancer (treatment or palliation within 6 months) (1)
4 or less: D-dimer to exclude. If +ve arrage CT angiogram
>4: Immediate CT angiogram

34
Q

What is the first line empiric anticoagulation for a suspected DVT?

A

DOAC e.g. apixaban, rivaroxaban

35
Q

What are the 2 most likely causes for Fibrinogen deficiency?

What clotting factor is fibrinogen?

What results are expected from PT and aPTT

A

DIC and Liver disease

Clotting factor I (common pathway)

Since it is part of the common pathway, both will be prolonged

36
Q

What are the most common drugs that may cause thrombocytopaenia? (5)

A

Heparin
Antiplatelets (clopidogrel/tecagrelor)
Quinines/anti-malarial medication
Antibiotics (vancomycin)
DMARDs/Chemotherapy drugs (methotrexate, cisplatin)
NSAIDs

37
Q

What infections (3) may lead to thrombocytopaenia?

A

HIV
EBV
Malaria

38
Q

A 78 year old gentleman is admitted to ICU with a severe community acquired pneumonia on a background of COPD. His condition does not improve despite aggressive antibiotic therapy. On the fourth day in the unit the nursing staff note bleeding around his indwelling venous lines. Lab results show:
PT 29.5s (13-17s)
aPTT 66s (26-39s)
Ddimer 5μg/mL (<0.5 μg/mL)
Platelets 30 x 109/L (140 x 109/L)

What is the most likely diagnosis?
What additional tests (2) as part of the coagulation screen may inform treatment? Include expected results

A

DIC
Fibrinogen (low)
Thrombin time (prolonged)

39
Q

A 34 year old pilot is noted on routine screening to have a platelet count of 55 (normal range 150-400). He has no history of bleeding disorders, no personal
medical history, or relevant family history).

Give 5 ddx for the possible causes

A

Thrombocytopaenia ddx: Must either be

I - Reduced production of platelets
Leukemia
Metastatic Cancer
Aplastic anaemia

II- Increased consumption of platelets:
Immune: autoimmune thrombocytopenia, TTP
Infection: HIV, EBV, malaria
Splenomegaly/hypersplenism
DIC

III- Drug-induced (heparin, antiplatelets, vancomycin, anti-malarial, methotrexate, cisplatin, NSAIDs)

40
Q

The most common agents for Anticoagulation are heparin, warfarin, and DOACs. What are 5 indications?

A

1) Tx of PE/DVT (venous thromboembolism)
2) Prevention of PE/DVT post-op/high risk patients
3) Treatment of ACS
4) Primary/secondary stroke prevention in patients with A.fib
5) Prevention of valve thrombosis and stroke in patients with mechanical heart valves

41
Q

What is the MOA of Warfarin?
How is it monitored?
Give the 2 main indications?
How is it administered

A

Inhibits Vitamin K epoxide
Monitored via INR

Primary/secondary stroke prevention in patients with A.fib (2-3)
Prevention of valve thrombosis and stroke in patients with mechanical heart valves (2.5-3.5/3-4)

Administered orally OD

42
Q

Give the MOA of LMWH
How is LMWH monitored?
How is it administered?

A

Inactivates Factor Xa

No monitoring required but if needed, anti-factor Xa activity

Adminsterd SC OD/BD

43
Q

Give the MOA of Unfractionated Heparin
How is it administered? (specifics)
How is it monitored? (specifics)

A

Inhibits factor IXa, Xa, and Thrombin by binding to Antithrombin
Administered as 5000IU bolus followed by 1000IU/hr

Monitored by aPTT (intrinsic pathway) every 4-6 hours

44
Q

Give the MOA of DOACs
Do they require monitoring?

A

Factor Xa “xabans” inhibitors (no monitoring needed)
Dabigatran is a Direct thrombin inhibitor (needs monitoring)

45
Q

A 23 year old male presents with a painful knee joint following a minor fall at home. Examination demonstrates crepitus, severe tenderness and a positive patellar tap. An aspiration is performed which reveals frank blood. He tells you his brother had a similar problem last year. Which of the following investigation results is likely to be found in this case?
A. Normal PT, prolonged APTT
B. Normal APTT, prolonged PT
C. Normal PT, normal APTT
D. Prolonged PT, Prolonged APTT
E. Decreased PT, Decreased APTT

A

A

Have arthritis is characteristic of haemophilia (factors 8 or 9 deficiency)

A platelet disorder on the other hand or Alexander’s disease (factor 7) more so has mucocutaneous bleeds

46
Q

A 67 year old man is admitted for elective repair of an abdominal aortic aneurysm. He has a history of atrial fibrillation and is on warfarin therapy for this. His warfarin is discontinued on admission and he is placed on unfractionated heparin. You are the intern on call and are asked to titrate his heparin dosage. Which of the following investigations will you perform prior to changing the prescription?
A. APTT
B. PT
C. INR
D. Factor Xa levels
E. Thrombin

A

A

47
Q

What are the contraindications to using anticoagulants? Give 5

A

Recent Haemorrhagic CVA
Recent major trauma
Active gastroduodenal ulcer
Bleeding disorders/ coagulopathy/ haemophilia
Severe hypertension
Thrombocytopaenia
WARFARIN ONLY - Teratogenic => CI in pregnancy

Data Interpretation (9 decks)

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