HIT

Question 1

HIT basic mechanism

Answer 1

antibodies to PF4

Question 1

How to rule out platelet clumping

Answer 1

• citrated tube (use sodium citrate as reagant, not EDTA)

Question 2

4 T’s are -

Answer 2

• new thrombosis or *skin necrosis
• Thrombocytopenia
• timing (Clear onset between days 5 and 10 or platelet count fall at ≤1 day if prior heparin exposure within the last 30 days – 2 points)
• other causes for thrombocytopenia not apparent

Question 3

Is the SRA or ELISA a better test for HIT?

Answer 3

SRA - higher sensitivity and specificity

Question 4

1) HIT management 2) Anticoagulants that are contraindicated

Answer 4

• no heparin or LMWH
• *warfarin contraindicated (can cause protein c and s and worsen complications, particularly skin necrosis)

Question 5

HIT and HITT duration of anticoagulation

Answer 5

• 3 months if no VTE
• ?

Question 6

Autoimmune HIT management

Answer 6

High dose IVIG

Question 7

Other HITT complication aside from clotting to be aware of

Answer 7

1) Post-UFH bolus anaphylactoid reaction can also occur
2) Coumarin necrosis, especially venous limb gangrene

Question 8

What is venous limb gangrene?

Answer 8

Limb gangrene in the same lim as you have a DVT due to microvascular thrombosis
*Typically have a DIC state and high INR

Question 9

Clotting factors with the shortest half lives

Answer 9

protein C
factor VII

Question 10

Timeline for VITT

Answer 10

5-30 days

Question 11

Relatively common sites of clotting with VITT

Answer 11

CVT
*splanchnic vein thromnboses

Question 12

Lab features of VITT + results of HIT testing

Answer 12

• thrombocytopenia and DIC type picture w/ low fibrinogen + high d- dimer
• HIT ELISA positive but rapid tests typically negative

Question 13

VITT management

Answer 13

1) high dose IVIG
2) anticoagulation - DOAC per UTD, heparin per HIT expert