Hemostasis problem solving

Question 1

PLT low & viral infection, what would you consider? (1)

Answer 1

ITP

Question 2

Bleeding & Prolong APTT, what would you consider? (1)

Answer 2

vWF / Factor 8, proceed to vWF study & PLT aggregation test

Question 3

Suggest 3 tests to study vWF subtype and describe how to interpret the results (5)

Answer 3

VWF:Ag very low = type 3
VWF:Ag low, VWF:Rco & VIII:C normal = normal
VWF:RCo/VWF:Ag & VIII:C/VWF:Ag >=0.7 = type 1
VWF:RCo/VWF:Ag <0.7 = type 2A/B/M, proceed to RIPA
VIII:C/VWF:Ag <0.7 = 2N / Haemophilia A

Question 4

Patients on Heparin develop thrombosis, what would you consider? (1)

Answer 4

HIT

Question 5

Prolong APTT, corrected immediately on mixing study but prolong after 2h, what would you consider? (1) What are the 2 other conditions that can be differentiated using mixing study? (2)

Answer 5

Consider factor 8 inhibitor
Not corrected at all consider LA
Corrected in both consider deficiency

Question 6

Low MCV with Target cell, what would you think of? (1) How to rule out the other possibility? (1) How about High MCV with Target cell? (1)

Answer 6

Low MCV, Target cell, MCV/RBC>13 = IDA, <13 = Thal
High MCV, Target cell = liver disease (AST/ALT>1 = cirrhosis)

Question 7

How can APTT be corrected to normal in a Mixing study when a patient’s plasma with deficient factor (down to 0%) mixes 1:1 with normal plasma (100%)? (1)

Answer 7

It works because 50% factor is sufficient to correct a prolonged APTT

Question 8

PT of sample stored at 4C would be shortened, why? (1)

Answer 8

due to cold activation of factor 7

Question 9

Describe testing protocol for heparin monitoring (2)

Answer 9

baseline APTT & PLT is taken, than every 6h draw again
If PLT <50%, consider HIT

Question 10

Suggest a condition causing spontaneous abortions (1)

Answer 10

APS
No bleeding unless PLT low

Question 11

Patient on warfarin before liver biopsy shows INR 4.5, why is that? (1) What should physicians do next? (4)

Answer 11

INR high due to cirrhosis
Stop warfarin immediately
Give vitamin K, access PT 4 days later, as Cholestasis affects vitamin K absorption

Question 12

Why should APTT be analyzed within 4 h? (1)

Answer 12

because factor 5&8 are labile

Question 13

If heparin is effective in preventing thrombosis, why change to warfarin? (1) Describe when would you change to warfarin & when would stop heparin (2) Why overlapping period is required instead of just replacing heparin with warfarin? (1)

Answer 13

Warfarin has longer half life for extent period of thrombotic risk prevention.
Heparin to Warfarin when APTT>1.5UL
Heparin warfarin overlap period to prevent thrombotic event caused by warfarin inhibition on protein C & S
Stop heparin when INR=2~3