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Flashcards in Screening Tests Deck (25):
1

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

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

2

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

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

3

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

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

4

Screening tests v.s definitive test

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

5

PT:
- principle

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

6

PT:
- method of activation

Addition of the reagent - tissue thromboplastin + calcium

7

PT:
- factors being measured

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

8

PT:
- factor deficiencies/conditions yielding abnormal results

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

9

PT:
- Reference range

10-13 seconds

10

APTT:
- principle

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

11

APTT:
- method of activation

Particulate activator (neg charged surface)

12

APTT:
- factors being measured

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

13

APTT:
- factor deficiencies/conditions yielding abnormal results

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

14

APTT:
- Reference range

20-35 seconds

15

ACT:
- principle

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

16

ACT:
- method of activation

Diatomaceous earth

17

ACT:
- factors being measured

Heparin inactivated serine proteases in the intrinsic pathway:

XIIa, Fletcher, XIa, IXa, Xa, Thrombin

18

ACT:
- factor deficiencies/conditions yielding abnormal results

?

19

INR:
- definition

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

20

INR:
- anticoagulant therapy that it manages

Manages coumadin anticoagulant therapy (along with the prothrombin time)

21

INR:
- implications of an INR less than two

at risk to from new clot

22

INR:
- implication of an INR over 4

bleeding risk

23

Thrombin Clotting Time:
- principle

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

24

Thrombin Clotting Time:
- conditions yielding prolonged results

- Afribrinogenemia, Hypofibrinogenemia, Dysfibrinogenemia
- "Antithrombins" (Heprin and FDPs)
- "circulating anticoagulants"
- DIC
- Thrombin inhibitors (Pradaxa)
- NOT COUMADIN

25

Thrombin Clotting Time:
- purpose of substituting reptiles for thrombin (Reptilase time)

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.