Screening Tests

Question 1

What is the work-up of a patient for bleeding disorder according to patient history

Answer 1

Look for past bleeding episodes, past surgeries, family history, drug history
- Has the bleeding been out of proportion to the challenge/injury

Question 2

What is the work-up of a patient for bleeding disorder according to physical examination

Answer 2

Does type of bleed point to a disorder? (primary, secondary, both?)

Question 3

What is the work-up of a patient for bleeding disorder according to lab testing

Answer 3

• Manual
• Mechanical
• Photo-optical
• Chromogenic
• Immunological

Question 4

Screening tests v.s definitive test

Answer 4

Screening:

• Platelet Count
• Bleeding Time
• Prothrombin Time
• INR
• APTT
• Activated Clotting Time (ACT)
• Thrombin Clotting Time (TCT or TT)

Question 5

PT:

- principle

Answer 5

Tissue thromboplastin (containing calcium) is added to patient plasma; time required for a clot to form is measured

Question 6

PT:

- method of activation

Answer 6

Addition of the reagent - tissue thromboplastin + calcium

Question 7

PT:

- factors being measured

Answer 7

Extrinsic Pathway: VII, X, V, II, I

Question 8

PT:

- factor deficiencies/conditions yielding abnormal results

Answer 8

• Deficiency of factor(s)
• Liver disease
• Vit K deficiency
• Coumadin anticoagulant therapy
• Excessive amounts of heparin
• “circulating anticoagulants” aka “inhibitors to coagulation”
• DIC

Question 9

PT:

- Reference range

Answer 9

10-13 seconds

Question 10

APTT:

- principle

Answer 10

A phospholipid substitute for platelets (“partial thromboplastin”) along with a negatively charged particulate activator is added to patient plasma to activate contact factors
- Calcium is re-added and time required to clot is measured

Question 11

APTT:

- method of activation

Answer 11

Particulate activator (neg charged surface)

Question 12

APTT:

- factors being measured

Answer 12

Intrinsic Pathway:

XII (Fletcher and Fitzgerald), XI, IX, VIII, X, V, II, I

Question 13

APTT:

- factor deficiencies/conditions yielding abnormal results

Answer 13

• Deficiency of factor(s)
• Liver disease
• Heparin anticoagulant therapy
• Long term Coumadin anticoagulant therapy
• “circulating anticoagulants” aka “inhibitors to coagulation”
• DIC

Question 14

APTT:

- Reference range

Answer 14

20-35 seconds

Question 15

ACT:

- principle

Answer 15

An activator added to fresh whole blood and clotting time is measured (used in surgery to monitor heparin therapy)

Question 16

ACT:

- method of activation

Answer 16

Diatomaceous earth

Question 17

ACT:

- factors being measured

Answer 17

Heparin inactivated serine proteases in the intrinsic pathway:

XIIa, Fletcher, XIa, IXa, Xa, Thrombin

Question 18

ACT:

- factor deficiencies/conditions yielding abnormal results

Answer 18

?

Question 19

INR:

- definition

Answer 19

ratio between the time it takes normal blood to clot and “Coumadin blood” to clot

Question 20

INR:

- anticoagulant therapy that it manages

Answer 20

Manages coumadin anticoagulant therapy (along with the prothrombin time)

Question 21

INR:

- implications of an INR less than two

Answer 21

at risk to from new clot

Question 22

INR:

- implication of an INR over 4

Answer 22

bleeding risk

Question 23

Thrombin Clotting Time:

- principle

Answer 23

The reagent thrombin is added to plasma and the time required for clot formation is measured

Question 24

Thrombin Clotting Time:

- conditions yielding prolonged results

Answer 24

• Afribrinogenemia, Hypofibrinogenemia, Dysfibrinogenemia
• “Antithrombins” (Heprin and FDPs)
• “circulating anticoagulants”
• DIC
• Thrombin inhibitors (Pradaxa)
• NOT COUMADIN

Question 25

Thrombin Clotting Time:

- purpose of substituting reptiles for thrombin (Reptilase time)

Answer 25

It is capable of converting fibrinogen to fibrin (like thrombin) but it is unaffected by heparin. So it is helpful in testing for functional fibrinogen when the TCT is prolonged due to heparin.