Coagulation

Question 1

Manual Coagulation Reagent Formation

Answer 1

Neoplastin/PT: 10 mL of R2 in
- good for 2 days

Activated thromboplastin/APTT: 5 mL water

CaCl2

Normal and abnormal controls: 2 mL water

Question 2

Coagulation Sample Standards

Answer 2

9:1 ratio
Sodium citrate light blue tube
Platelet poor plasma (unless platelet aggregation studies)

Question 3

Coagulation Sample Errors

Answer 3

Underfilled: prolonged results from excess chelating of calcium
Hemolyzed: bad for photometric methods
Clotted: activated coag system, shorten results

Question 4

High Hematocrit Coagulation Sample Correction

Answer 4

High hematocrit = short draw, must correct

[(100 - %HCT) / (595 - %HCT)] x V
V = volume of blood, usually 5

Question 5

Sample Stability

Answer 5

APTT: 4 hours, room temp
PT, FIB, TT, D-DI: 8 hours, room temp
Samples can be frozen for longer stability

Question 6

Thrombocytopathy

Answer 6

Platelet count normal but functions are abnormal

Question 7

Platelet Aggregation

They bind to what?

Answer 7

Agonists ADP, thrombin, epinephrine, and collagen bind to receptors

Question 8

Aspirin

What does it inhibit? What does that form?

Answer 8

Inhibit cyclo-oxygenase which forms thromboxane

Question 9

PFA-100

What does it do, type of blood, process, problems, possible conditions

Answer 9

Screens for platelet function
Whole blood
Blood aspirated into membrane with collagen/epinephrine/ADP to stimulate aggregation, forms a plug - measures time it takes to plug as closure time
Affected by platelet counts <100 and hematocrit<30%, platelet clumping error, or patient took aspirin
VWB patients have prolonged closure time

Question 10

Prothrombin Time (PT)

Process, reference range, what it measures, what therapy

Answer 10

PPP + TTP + CaCl2 = fibrin clot
10-14 seconds
Measures extrinsic pathway
Coumadin therapy

Question 11

PT/INR

Why, formula

Answer 11

Standardize results between instrument and PT reagen

INR = (PT patient/PT normal)^ISI
ISI = international sensitivity index

Question 12

Activated Partial Thromboplastin Time (APTT)

Process, reference range, what it measures, therapy

Answer 12

PPP + Partial TP + particulate activator + CaCl2 = fibrin clot
25-36 seconds
Intrinsic pathway
Heparin therapy

Question 13

Automated Coagulation

Methods + what they do, what they are used in

Answer 13

Clot detection: measures time it takes for sample to form clot, used in PT, APTT, FIB, TT
Photometry: based on optical density, measures chromogenic reaction, used in D-Dimer

Question 14

FIB

Process, reference range, what it measures

Answer 14

Fibrinogen + 100 U thrombin = insoluble fibrin clot
200-400 mg/dL
Measures rate of fibrinogen to fibrin conversion in diluted sample

Question 15

Thrombin Time

Process, reference range, what it measures

Answer 15

PPP + thrombin = fibrin clot
13-20 seconds
Measures fibrin formation by action of thrombin

Question 16

PT + APTT Mixing Study

Correction? Dilution? Factors?

Answer 16

Corrects: factor deficiency
Does not correct: factor inhibitor
1:1 ratio of patient plasma to NP
PT: VII
APTT: XII, XI, IX,VIII (VIII and IX, most common)
Both: X, V, II, I

500 mL plasma + 500 mL NP

Question 17

Thrombin Time Mixing Studies

Limit reached to do study, correction, inhibitor study

Answer 17

<100 mg/dL
Corrects: fibrinogen deficiency
Does not correct: inhibitor
Mix with protamine sulfate (reverses heparin)
Inhibitor study corrects: heparin
Does not correct: inhibitor

Question 18

Factor Assay

Process, why dilute, ref range, dilution conversion, interpret curve

Answer 18

Patient plasma diluted with deficient plasma, any activity of factor is coming from patient, dilute 3 times

Dilute to see factor levels increasing as dilutions get higher

Normal levels 70-140%

Percentage gotten from curve multiplied by dilution

Don’t match within 15% but factor levels low: inhibitor
Don’t match within 15% but factor levels normal: unlikely factor inhibitor

Question 19

DIC Workup

What is it, test results, treatment

DIC is not a diagnosis! APL, burn pts, sepsis, etc.

Answer 19

Tissue damage leads to clotting with consumption of clotting factors which leads to bleeding

PT: increased
APTT: increased
TT: increased
FIB: decreased
D-Dimer: increased
VIII:C: decreased
CBC: low plateletts, schistocytes