Section 3

Question 1

Define plasma

Answer 1

liquid portion of blood; including water, proteins, salts, hormones

not clotted

Question 2

Define serum

Answer 2

• Fluid portion of the blood that remains after the blood has clotted.

Question 3

What is EDTA?

Answer 3

• color stopper is lav/purple
• function: mostly used in hematology (CBC, IPF, PFA, whole blood aggregometry) and molecular testing
• It is used to prevent blood from clotting by chelates calcium

Question 4

What is Sodium citrate?

Answer 4

• color stopper: light blue
• function: most commonly used in hemostasis
• binds calcium
• CBC reports only WBC and plts, we can use Sodium citrate as a substitute will multiply all values by 1.1 to correct dilution

Question 5

Why dos a sodium citrate tube must be full?

Answer 5

• needs to be at full for set anticoagulant in order to bind calcium . Ratio is 9 parts blood and 1 part citrate

Question 6

Discuss how an increase or decrease hematocrit can affect a coagulation specimen

Answer 6

• When a patient has a hematocrit greater than 55%, the plasma volume will be too low for the amount of sodium citrate solution in the tube. This may lead to false increase of the Protime INR or aPTT results because of excess anticoagulant.

Question 7

Differentiate the uses of platelet poor plasma (PPP) and platelet rich plasma (PRP) in coagulation studies.

Answer 7

Optical Aggregometry (Light Transmittance)
* Add aggregating agent to PRP
* PPP is a blank

Principle:
* Platelets aggregate
* Plasma becomes clearer as platelets aggregate
* Turbidity decreases and light transmitted increases

Question 8

List test abbreviations. State reference ranges (see OHSU reference ranges and class notes). Discuss the principle and purpose of test. List the factors or components measured as well as those that are added as reagents or part of reagents. Interpret results: Immature Platelet Fraction (IPF)

Answer 8

• Measure of immature (reticulated) platelets in the peripheral blood
• Reflects presence of RNA

Low to normal IPF = decreased production
* Aplastic anemia, leukemia, bone marrow suppression, drug effect
Increased IPF= platelet destruction
* ITP, TTP, DIC, drug effect, etc.

Good to know if the bone marrow is responding to bleeding

Question 9

List test abbreviations. State reference ranges (see OHSU reference ranges and class notes). Discuss the principle and purpose of test. List the factors or components measured as well as those that are added as reagents or part of reagents. Interpret results: Capillary fragility

Answer 9

Evaluates vascular integrity- can suggest Dangi fever

Procedure:
* Examine arm and back of hand for any petechiae.
* Apply blood pressure cuff. Apply pressure midway between systolic and diastolic pressures. (usually between 70 -90 mm Hg)
* Leave cuff on for 5 minutes.
* Remove cuff and wait 5 -10 minutes before looking for petechiae. Count # on forearm 1/2 inch below cuff and just above the wrist. May also use back of hand.

Question 10

List test abbreviations. State reference ranges (see OHSU reference ranges and class notes). Discuss the principle and purpose of test. List the factors or components measured as well as those that are added as reagents or part of reagents. Interpret results: Closure time - Platelet Function Anaylzer (PFA-100)

Answer 10

Tests primary (plt) hemostasis in an artificial vessel, simulating the in vivo process of platelet adhesion, activation and aggregation
* Tests whole blood
* Test cartridges with biochemically active membranes
* Collagen /ADP
* Collagen / epinephrine

Question 11

List test abbreviations. State reference ranges (see OHSU reference ranges and class notes). Discuss the principle and purpose of test. List the factors or components measured as well as those that are added as reagents or part of reagents. Interpret results: Platelet aggregation

Answer 11

Adding an aggregating agent such as Thrombin, Collagen, Epinephrine, ADP etc. to patients PRP.
* The primary phase of aggregation is initiated by adding the agent.
* The second phase of aggregation is achieved after a successful platelet release reaction.

Question 12

List test abbreviations. State reference ranges (see OHSU reference ranges and class notes). Discuss the principle and purpose of test. List the factors or components measured as well as those that are added as reagents or part of reagents. Interpret results: von Willebrand factor activity - Ristocetin co-factor (vWF: RCo)

Answer 12

It is not actually accomplishing aggregation. The platelets are sticking together with vWF. Thus it more closely mimics the process of platelet adhesion.
* This is why the Ristocetin aggregation curve is abnormal in von Willebrands disease and Bernard Soulier.
* If the patient has von Willebrands disease this curve will be abnormal but their plt curve will be normal. This will also happen if the pt lacks GP1b.

Question 13

List disorders that can cause a prolonged closure time (PFA-100)

Answer 13

Platelet defect/ vW disease
Asprin/ drug-like effect

Question 14

State two patient factors that can influence the PFA assay.

Answer 14

a HCT< 35% or a PLT <150,000

Question 15

Discuss reasons why the PFA closure time has replaced the historic Bleeding Time assay.

Answer 15

Bleeding time assay is very hard to standardize (blood pressure, plt numbers, size, depth and placement of the cut, subjective)
Bleeding time only looks at plts and fibrinogen since its the microvasculature

Question 16

Platelet Aggregation

Answer 16

GP2b/3a to Fibrinogen (Factor 1)

Question 17

Discuss the principle of the platelet aggregometer.

Answer 17

• Shape Change
• Primary aggregate- direct aggregation by agent
• Release reaction (blue shoulder in picture)
• Secondary aggregation- mediated by release rxn
• Plasma becomes clearer as platelets aggregate
• Turbidity decreases and light transmitted increases

Question 18

Optical (light transmission) - reference method

Answer 18

Add aggregating agent to PRP
PPP is blank

Principle:
* Platelets aggregate
* Plasma becomes clearer as platelets aggregate
* Turbidity decreases and light transmitted increases

Question 19

Whole Blood (impedance)

Answer 19

Principle:
* Platelets aggregate
* Platelets adhere to electrode and one another
-impedes the DC current
* The rise in impedance is directly proportional to platelet aggregation
* Tracing is similar to light transmittance aggregometry

Question 20

Luminaggregometry

Answer 20

• Provides a clearer measure of platelet secretion so a perfect biphasic curve isn’t necessary
• Can be done at the same time as whole blood or light transmittance aggregometry
• Thrombin induces full secretion
• As ATP is released, it oxidizes a firefly-derived luciferin-luciferase reagent to generate cold chemiluminescenceproportional to the ATP concentration.