Laboratory Evaluation of Hemostasis

Question 1

Hemostasis is dependent upon which factors?

5

Answer 1

1. Vessel Wall Integrity
2. Adequate Numbers of Platelets
3. Proper Functioning Platelets
4. Adequate Levels of Clotting Factors
5. Proper Function of Fibrinolytic Pathway

Question 2

Which three ways does the body achieve and make a stable hemostatic plug?3

Answer 2

1. Blood Vessel Constriction (vasoconstriction)
2. Platelet Aggregation (ahesion and activation too)
3. Coagulation Cascade

Question 3

What lab tests do we want to do for evaluation of hemostasis?
5

Answer 3

PLATELET COUNT (plt)
BLEEDING TIME (BT)
PROTHROMBIN TIME (PT/INR)
ACTIVATED PARTIAL THROMBOPLASTIN TIME (aPTT)
THROMBIN TIME (TT)

Question 4

What is the platelet count measuring?

What tube is it collected in?

Answer 4

The number of platelets per cubic millimeter of whole blood

Its on the CBC

Lavender top (EDTA)

Question 5

What are the different ways to count platelets?

Answer 5

1. Manual platelet counting
2. Automated cell counter methods
   - Optical counting methods
   - Flow cytometric methods
3. Platelet count ratio method for platelet function testing

Question 6

Whats a normal platelet count?

What platelet count is considered thrombocytopenia?

What is considered mild thrombocytopenia?

What is consodered severe thrombocytopenia?

Answer 6

Adults: 150,000-450,000/mm3
Peds: 150,000-350,000 /mm3

Below 150,000

50,000-99,999 Mild

Question 7

At what platelet count do you start experiencing symtpoms?

What count is potentially life threatening?

At what count are you at high risk for spontaneous bleeding and intracranial hemorrhage?

Answer 7

50,000 - 20,000: first symptoms

20,000-10,000

Below 10,000

Question 8

If you have a high platelet count what could be happening?

5

Answer 8

1. Acute phase reaction (most prominent is C reaction protein CRP)
2. Early CML
3. Essential thrombocytosis
4. Polycythemia vera
5. Post splenectomy (very common)

Question 9

If you have a low platelet count what could be happening?

7

Answer 9

1. DIC (sepsis and trauma)
2. Hemolytic anemia
3. Hypersplenism
4. ITP
5. Leukemia
6. Prosthetic heart valve
7. Recent transfusion

Question 10

What does bleeding time measure?

Whats it a screening test for?

What is it useful for and what is it not useful for?

Answer 10

A measurement of the time required for bleeding from a superficial puncture to stop.

Platelet funtion

Not a reliable predictor of post-op bleeding

Useful in the diagnosis of Von Willebrand’s

Question 11

What does bleeding time really measure?

Answer 11

how well platelets interact with blood vessel walls to form blood clots.

Question 12

How often should we blot in a bleeding time test?

Answer 12

Blot incision q 30 seconds until bleeding stops

Question 13

What should we avoid 2 weeks prior to a bleeding time test?

Whats the normal bleeding time?

Answer 13

Avoid aspirin 2 weeks prior to test

Normal: 3-8 minutes

Question 14

What could indicate a high bleeding time?

7

Answer 14

1. Platelet dysfunction
2. DIC (but probably won’t do the test here)
3. Leukemia
4. Liver disease
5. Thrombocytopenia
6. Von Willebrand’s
7. Vasculitis

Question 15

What does prothrombin time measure?

Answer 15

Measures vitamin K dependent clotting ability, and extrinsic pathway

Question 16

What is PT used to screen and monitor?

2

Answer 16

Used to screen for bleeding disorders

Used to monitor patients on warfarin

Question 17

What is prothrombin time lab filled in and how do we need to fill it?

Answer 17

Light blue top (citrate)
Fill tube completely
Avoid prolonged tourniquet use (hemoconcentration, hemolysis, lactic acid buildup. no more than 1 minute)
Correct ratio of blood to citrate is critical
prolonged storage of plasma shortens PT

Question 18

Whats a normal PT?

For DVT prophylaxis what do we want the INR to be?

For Mechanical valve and anti-phospholipid antibody syndrome what do we want the INR at?

What should we treat pregnant women with?

What should AFIB pts INR be at?

Answer 18

Adults PT/INR: 11-13 seconds 1-2

DVT prophylaxis (INR): 2-3

2.5-3.5

(can cause a lot of complications in pregnancy. treat with warfarin or aspirin but in pregnant women go for heparin)

2-3

Question 19

What conditions would be indicated with a high PT/INR?

5

Answer 19

1. Anti-phospholipid antibody syndrome
2. DIC
3. Liver disease
4. Vitamin K deficiency
5. Factor II, V, VII, or X deficiency

Question 20

What is PTT?

What does it measure?
Which is generally measuring what?

Answer 20

ACTIVATED PARTIAL THROMBOPLASTIN TIME

A measure of the time taken for a clot to form in citrated blood following the addition of calcium and a phospholipid platelet substitute.

Effectiveness of the intrinsic pathway

Question 21

What is PTT used to work up, monitor, and screen?

3

Answer 21

Used to work up bleeding disorders
Used to monitor heparin therapy
Screen for lupus anticoagulant

Question 22

What do we collect PTT in and what do we need to remember to do while filling it?

Answer 22

Light blue top (citrate)
Fill tube completely
Avoid prolonged tourniquet use
Correct ratio of blood to citrate is critical 
prolonged storage of plasma shortens PTT

Question 23

Whats the normal PTT in adults?

What about on antocoagulation therapy?

What is the normal PTT in peds?
Newborns:
1-6 yrs old:

Answer 23

Adults: 25-35 secs

On anticoagulant therapy: 1.5-2.5 x the control value

Newborn: 31-54 secs
1-6 yrs: 24-36

Question 24

What conditions would be indicated in a high PTT?

5

Answer 24

Hemophilia
DIC
Liver disease
Vitamin K deficiency
Heparin therapy

Question 25

What lab is associated with the intrinsic pathway and what factors is it associated with? 4

Answer 25

``` Think PTT (partial thromboplastin time) Think VIII, IX, XI, and XII ```

Question 26

What lab is associated with the extrinsic pathway and what factors is it associated with?2

Answer 26

Think PT(INR) (prothrombin time) Think II and VII

Question 27

What factors are vitamin K dependent?

Answer 27

Factors VII, X, and prothrombin (Factor II)

Question 28

What is thrombin time measuring? Whats the normal thrombin time?

Answer 28

The rate of conversion of fibrinogen to fibrin in the final stage of coagulation as measured by the addition of thrombin to citrated blood. Fibrinolytic pathway 15-20 secs

Question 29

What do we collect thrombin time in?

Answer 29

Light blue top (citrate) Fill tube completely Avoid prolonged tourniquet use Correct ratio of blood to citrate is critical

Question 30

What would indicate a high thrombn time? | 6

Answer 30

1. DIC 2. Liver disease 3. Dysfibrinogenemia (abnirmal fibrinogen funtion- could cause 4. bleeding or thrombosis) 5. Paraprotienemia-monoclonal gammapathy 6. Uremia

Question 31

What would a low thrombin time? | 2

Answer 31

Erythrocytosis | Dysfibrinogenemia

Question 32

Indications to order coagulation studies ? | 5

Answer 32

1. Work-up of suspected bleeding disorders 2. Screening before major surgery, part of pre-op evaluation 3. Monitoring of medications (warfarin, heparin) 4. Monitoring of bleeding disorders 5. Monitoring of liver disease

Question 33

What pathway are we monitoring with heparin?

Answer 33

intrinsic/pt

Question 34

What pathway are we monitoring with warfarin?

Answer 34

extrinsic and ptt

Question 35

Whatdo we really want to know when someone presents with abnormal bleeding?

Answer 35

What is the bleeding site? ``` Multiple vs single sites Joints Deep muscle Superficial cut Skin or mucus membrane Epistaxis Gingivae Urine, GI tract, Menstrual ```

Question 36

Platelet/cellular deficiency or malfunction will show bleeding where? 5 What will be normal and abnormal? 2

Answer 36

``` Gum bleeding Easy bruising Epistaxis Petechiae Prolonged bleeding from minor cuts ``` Abnormal bleeding time, normal PT/PTT

Question 37

Factor deficiencies (hemophilia) will show bleeding where? 5 What will normal and abnormal in the lab tests? 2

Answer 37

``` Hemarthroses Easy bruising Delayed bleeding Postop hemorrhage Muscle hematoma ``` Normal bleeding time, abnormal PTT