10.16.18 Hemostasis Assays

Question 1

What are the routine coagulation tests?

Answer 1

1. Prothrombin Time (PT)
2. Activated Partial Thromboplastin Time (aPTT)
3. Thrombin Time (TT/TCT)

Question 2

What is measured in TT

Answer 2

Formation of fibrin by adding thrombin (DON’T NEED Ca, or PL)

Question 3

What causes a prolonged TT?

Answer 3

1. Low fibrinogen
2. Abnormal fibrinogen
3. Inhibitor of added thrombin- heparin, dabigatran, argatroban

Question 4

What is measured in PT?

Answer 4

Extrinsic pathway

- Add thromboplastin (TF and PL) and Calcium and measure until clot forms

Question 5

What causes prolonged PT?

Answer 5

1. Anything that prolongs TT
2. Anything that inhibits the common pathway factors (10,5,2,1)
3. Low levels of F7

Question 6

How do we get low levels of factor 7?

Answer 6

1. Congenital
2. Deficiency of Vit K
3. Vit K Inhibitors
4. DIC
5. Liver Disease

Question 7

What are sources of Vit K and what causes deficiency?

Answer 7

Source

1. Green leafy veggies
2. Gut flora

Deficiency

1. Being a newboard
2. Diet
3. Antibiotics
4. Fat malabsorption

Question 8

What is a normal value for INR?

Answer 8

1

Question 9

What is measured in aPTT?

Answer 9

Intrinsic pathway; partial thromboplastin is missing TF but has PL
- Add Ca and Partial Thromboplastin to plasma till clot forms

Question 10

What causes a prolonged aPTT?

Answer 10

1. Problems with factors in common pathway (2,5,10,1)
2. Problems with contact factors (7, HMWK, PK)
3. Problems with Hemophilia
   (11-C, 9-B, 8-A)
4. Warfarin/severe Vit K deficiency
5. Heparin
6. Lupus inhibitor

Question 11

Autoantibody directed against PL; prolongs coagulation reactions in test tube and prolongation is blocked by adding more PL to reaction mix

Answer 11

Lupus inhibitor

Question 12

What is the broad differential for a prolonged aPTT?

Answer 12

1. Factor deficiency

2. Inhibitor

Question 13

If a 1:1 mixture of a normal plasma with patient plasma decreases aPTT what caused the long aPTT?

Answer 13

Factor deficiency

Question 14

For factor deficiencies, the higher up the PTT pathway you go, the _____ the PTT value

Answer 14

higher

also less clinically significant in terms of bleeding risk

Question 15

What if both PT and PTT are prolonged?

Answer 15

1. Deficiency of common pathway factor
2. Excess warfarin/heparin
3. Multiple factor deficiency (liver disease, DIC)

Question 16

How long it takes for flow in Platelet Function Analyzer (PFA-100) to stop which gives diagnostic information

Answer 16

Closure time

Question 17

What makes PFA-100 prolonged?

Answer 17

1. Low platelet count
2. Low Hb
3. Low VWF
4. Abnormal platelet function