7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
1/31
Bleeding Time, Clotting Time,
Prothrombin Time/PTT
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
2/31
Platelets (Thrombocytes)
Function interact with injured vascular wall
structures, plasma proteins, other circulating
blood cells
a. Adhesion: adhere to basement membrane of
injured blood vessel
b. Release action: release of alpha & dense
granules, & lysosomesc. Aggregation: formation of secondary, irreversible
platelet aggregation
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
3/31
Coagulation:
Starts with activation ofThromboplastin, from
injured tissue
Fibrinolytic System: Endothelial cells
Heparin
Antithrombin
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
4/31
Evaluation of Coagulation Factor Disorders
Medical History:
1. Symptoms
2. Onset of Bleeding
3. Location of Bleeding (?)
4. Family History
5. Drugs & Medications (?)
6. Other Systemic diseases
Physical Exam:
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
5/31
Laboratory Screening Tests
1. Prothrombin Time (Protime/PT)
2. Partial Thromboplastin Time (PTT)
3. Platelet count
*If abnormal add:
1. Bleeding Time2. Clotting Time
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
6/31
I. Prothrombin time /Protime/PT
Screen for deficiencies in: Extrinsic Pathway
FI, FII, V, VII, X
Test of choice for monitoring anticoagulant
therapy by Vit K antagonists (II, VII, IX, X)
Principle: Thromboplastin + Platelet-poorplasma & Ca++ react w/ FVII to activate FX ---
convert Prothrombin to Thrombin
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
7/31
Specimen source:
Citrated platelet-poor plasma (PPP) Reference Range: Values differ
10 12 seconds or 12 14 seconds
Reporting:
1. Patient time in sec w/ Ref range
2. Patient time in sec w/ control time
3. Prothrombin ratio (PT divided by mean of Ref
range multiplied by 100)
4. Percent Activity (outdated?)
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
8/31
5. International Normalized Ratio (INR):
- Widely used nowadays
- Comparison of Patient value with the normal value =
result is normalized to an international referencepreparation (IRP) of thromboplastin
- Values usually provided by manufacturers of
reagents
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
9/31
Interpretation of results:
Sensitivity: detect deficiencies of
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
10/31
II. Partial Thromboplastin Time (PTT)
Test of choice for factor deficiencies of the
Intrinsic & Common Pathway
Test of choice for monitoring Heparin therapy
PTT Reagent: 2 ocmponents
1. Platelet substitute (phospholipid) prepared from
brain & plant phospholipids
2.Activator- Kaolin, Celite, micronized silica, or
ellagic acid
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
11/31
Specimen source:
Citrated platelet-poor plasma (PPP)
Reagents:
Phospholipid w/ Activators (PTT reagent)
0.025 M CaCl2
Procedure: PPP (0.1mL) + 0.1mL PTT reagent,incubate at 37C for 3-5min, + 0.1mL warm CaCl2.
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
12/31
Reporting:
Reported in seconds, to the nearest tenth, along
with reference range.
Reference range: vary according to reagent,
method, instrument used
Lower limit of 20 sec to an upper limit of 45 sec
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
13/31
Interpretation:
Prolonged PTT in the absence of Heparin use
indicate:
Factor deficiency
Acquired circulating anticoagulant (e.g. Lupus inhibitor)
Antibody to a specific Factor (e.g. anti-FVIII)
Prolonged PTT if factor measured is
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
14/31
Sources of Error:
1. Sample collection & preparation
a. Improper collection & specimen processing
b. Incorrect anticoagulant-to-plasma ratio
c. Hemolysis
d. Platelets in plasma sample
e. Unexpected heparin contamination
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
15/31
2. Reagent preparation
a. Improper storage
b. Water impurities
c. Incorrect dilution
3. Instrumentation
a. Failing light source
b. Fluctuations in temperaturec. Loss of calibration of tubing
d. Contamination
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
16/31
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
17/31
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
18/31
III. Platelet Count
Formed in the BM from Megakaryocytes
Difficult to count:
a. Small & difficult to discern
b. Attached to surfaces/particles in diluting fluid
c. Disintegrate easily
d. Form clumps with other platelets
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
19/31
Specimen:
Capillary blood from finger puncture
Values are lower because of clumping at puncture site
Venous blood
EDTA (Lavender tube) as anticoagulant of choice
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
20/31
Method of Determination:
1. Manual Count
a. Unopette system
b. Hemacytometer
2. Automated Method
a. Optical methods
b. Impedance methods
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
21/31
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
22/31
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
23/31
Calculation: Manual Platelet Count
Ave # of Plt in 4 squares X 1mm2 x 100 X 106 = Platelets X 109/L
0.1 mm
Platelet Reference Range: 150 450 x 109/L
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
24/31
Clinical Significance:
Thrombocytopenia:
Platelet values lower than normal
Thrombocytosis:
Platelet values higher than normal
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
25/31
TESTS FOR PLATELET FUNCTION
1. Platelet Closure time
2. Platelet Aggregation Studies
3. Automated Platelet Function Analysis
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
26/31
Platelet closure time:
Assess platelet-related primary hemostasis; greateraccuracy & reliability than Bleeding Time (BT).
Instrument and test cartridge system which simulates theprocess of platelet adhesion and aggregation following avascular injury.
Rapid evaluation of platelet function on samples ofanticoagulated whole blood.
The time required to obtain full occlusion of the apertureis reported as the closure time (CT) in seconds.
Sensitive to platelet adherence and aggregation
abnormalities ; allows discrimination of aspirin-like defectsand intrinsic platelet disorder.
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
27/31
Platelet Aggregation Studies:
Measure response of platelet during hemostatic
process
Change in shape
Increase in surface adhesiveness Platelet plug formation
Use of Aggregating Agent
Measurement: Turbidimetry Method
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
28/31
CLOTTING TIME
Time required for a blood sample to coagulate/clot in
vitro under standard conditions.
Most common method: Capillary Tube Method.
Affected by calcium ion levels and many diseases.
Normal value: 5 to 8 minutes.
Time taken for blood to clot reflects time required for
the generation of thrombin
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
29/31
BLEEDING TIME
Principle: BT is the time it takes for a standard wound
to stop bleeding
Comprehensive test of platelet action in vivo & is
sensitive to the following abnormalities:1. Platelet numbers & function
2. Plasma VIII:vWF deficiencies
3. Vessel wall composition Standardization of Wound size is a problem
Employs BP cuff inflated at 40 mmHg
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
30/31
Reference range:
2 to 9 minutes
Considerations for the Test:
Volar skin must be dry Adequate incision/proper depth
Site should not touch filter paper
Aspirin& aspirin-containing meds must be discontinued 1
week prior to testing
NSAIDS must be discontinued 24 hrs prior to testing
7/28/2019 1. Dr. Agtuca - Bt, Ct, Pt & Ptt
31/31
Top Related