Hemostasis Testing

Question 1

Bleeding time

Answer 1

purpose: vasculature/platelets function in forming of primary hemostatic plug
principle: measure amnt of time it takes patient to form primary hemostatic plug
ref interval: 1-10 minutes

Question 2

Platelet count

Answer 2

purpose: quantitatively evaluate platelets
principle: count # of platelets
Sample: EDTA whole blood
ref int: 150-450,000/ uL

Question 3

Platelet function test

Answer 3

Purpose: qualitatively evaluate platelets
principle: measure amnt of time to form platelet plug while exposed to agonist
sample: Sodium citrate (blue top)
Interperet: increase Col/Epi & N Col/ADP = aspirin or anticoagulant drug
increase col/epi & increase col/ADP = platet function disorder

Question 4

Platelet Aggregation Studies

Answer 4

Purpose: qualitative
Principle: measure transmittance in plasma
Sample : Sodium citrate blue top
interperet: abnormal w/ ristocetin only = adhesion problem
abnormal w/ all BUT ristocetin = aggregation problem
abnormal secondary wave = secretion probolem

Question 5

Mean Platelet Volume (MPV)

Answer 5

function: measures avg platelet size
purpose: inversely proportional to plt count
Sample: EDTA whole blood
Interperetation: increase suggests thrombopoeisis secondary to thrombocytopenia
N suggests lack of thrombopoesis secondary to thrombocytopenia

Question 6

Immature Platelet Fraction (IPF)

Answer 6

Function: Indicates relative # immature platelets
Purpose: indicates etiology of thrombocytopenia
Sample: EDTA whole blood
Reference interval 1-5%
Interperation: In patient with thrombocytopenia
↑ - suggests platelets are being destroyed in peripheral blood
↓ – suggests that adequate platelet production/release in bone
marrow is not occurring

Question 7

How long are PT samples good for

Answer 7

24 hrs

Question 8

how long are aPTT and other assays good for?

Answer 8

4 hrs from time collected

Question 9

When to reject samples

Answer 9

– Not centrifuged within 30 minutes of collection
– Hemolysis
– Clotted samples
– Inappropriate sample to anticoagulant ratios
– Improper or inadequate storage

Question 10

Prothrombin Time (PT)

Answer 10

Purpose: screen for extrinsic/common pathway deficiencies, monitor oral anticoagulant therapy
Principle: measure time from activation of the extrinsic pathway to fibrin formation
Reagent: Tissue thromboplastin w/ Ca
Sample: Blue top sodium citrate
increased = extrinsic/common pathway deficiency or taking oral anticoagulants

Question 11

Thromboplastin reagent

Answer 11

Substitute for TF in vivo for PT test

Question 12

International Normalized Ratio (INR)

Answer 12

Purpose: monitor dosing oral anticoagulants
Principle: calculate w/ PT of patient and reagent constant
Interperet: 1.0 = normal (not on anticoags+
2.0 - 4.0 = therapeutic range
>5.0 = critical (decrease dose)

Question 13

aPTT (activated partial thrombolastin time)

Answer 13

Purpose: screen for intrinsic/common deficiencies, or monitor IV anticoagulants
Principle: Measure time from activation of intirnsic pathway to fibrin formation
Reagents: aPTT reagent( actin, cephaloplastin) and CaCl2
Interperetation: increase = intrinsic/common pathway factor deficiency, or inhibitor or on IV anticoagulants

Question 14

Thrombin Time

Answer 14

Purpose: Evaluate conversion fibrinogen to fibrin, screen for heparin
Principle: add excess thrombin to sample, measure time to clot
Sample: Sodium Citrate Blue top
Interperet: incr= deficiency of fibrinogen, presence of heparin, FDP’s or plasmin

Question 15

Fibrinogen Assay

Answer 15

Purpose: quantiative amnt fibrinogen
principle: TT is inverse propotional to fibrinogen concentration, standard curve w/ thrombin time plug into curve
Reagent: Thrombin Reagent
Sample: Blue top sodium citrate
Interperet: incr= not significant
dec= fibrinogen deficient, or inhibitors

Question 16

Reptilase Time (RT)

Answer 16

screen for heparin w/ TT
Principle: same as TT, different reagent (NOT AFFECTED BY HEPARIN)
Reagent: Reptilase
sample: blue top sodium citrate
interperet: incr: fibrinogen deficiency

Question 17

Urea Solubility Test

Answer 17

Purpose: deficiency in FXIII
Prin: unstable firbin is soluable in 5M ure after 24 hrs
Sample: sodium citrate blue top
Interpret: clot disappears <24 hrs = FXIII deficient

Question 18

Mixing Study

Answer 18

Purpose: differentiate between true factor deficiency and an inhibitor
Reagent: Normal Reagent Plasma
Sample: Blue top sodium citrate
Interpret: corrected = factor deficiency
uncorrected= inhibitor

Question 19

Factor Assay

Answer 19

Purpose: quantitative measure coag factors
Prin: PT/aPTT test w/ substrate plasma
Reagent: Substrate plasma = known to be deficient w/ factor of interest
Interpret: Decreased if patient is deficient in factor analyzed

Question 20

Bethesda Assay

Answer 20

Factor Inhibitor test (not often performed)

Question 21

FDP/ FSP’s

Answer 21

Purpose: detect fibrinolysis products
Prin: agglutination reaction w/ latex reagent
Sample: Sodium Citrate Plasma (Blue Top)
Interpret: increase=conditions w/ thrombosis (DVT, myocardial infarction, pulmonary embolism, etc)

Question 22

D-Dimer

Answer 22

Purpose: To detect D-Dimer fragments during fibrinolysis
Prin: Latex reagent w/ antibodies specific for D-Dimer
Sample: Sodium Citrate Plasma (Blue-Top)
Interpret: Incr: conditions w/ increased fibrinolysis(DVT, DIC)