Heparin induced thrombocytopenia

Question 1

Scoring system used for HIT + what’s included

Answer 1

4T
Thrombocytopenia (Nadir >20K)
Timing of platelet count fall
Thrombosis 
No other cause for thrombocytopenia

Question 2

Clinical features of Type 2 HIT

Answer 2

onset 5 to 10 days after heparin exposure + mean nadir platelet count 60k (those are only really 2 specific variables)

Question 3

Management

Answer 3

Stop heparin → switch to therapeutically dosed argatroban, fondaparinux, or rivaroxaban (argatroban typically because of shorter duration) (ASH)
IF using warfarin → wait until platelet count recovers to > 150,000/µL, then start warfarin for 3-6 months
Bilateral Lower extremity US for DVT

Question 4

Options + preferred AC for HIT

Answer 4

argatroban, fondaparinux, or rivaroxaban (argatroban typically because of shorter duration)

Question 5

Tests used for HIT testing

Answer 5

1) ELISA for HIT antibody

2) Serotonin release assay -

Question 6

How does serotonin release assay work

Answer 6

Functional assay – Measures ability of patient serum to activate test platelets in the presence of heparin

Question 7

Type 1 HIT pathophys + clinical course + clinical relevance

Answer 7

• not antibody mediated, direct effect on platelets
• mild drop within a few days of starting heparin.
• The typical platelet count nadir is approximately 100,000/microL.
• not considered clinically significant, no thrombosis, and patients can be managed expectantly without discontinuation of heparin.

Question 8

Type 2

Answer 8

Antibody mediated, more severe.

Question 9

when do you send SGRA?

Answer 9

Intermediate probability of HIT

Question 10

Management of type 1 HIT

Answer 10

• observe

- Don’t need to stop heparin.

Question 11

why you can’t use warfarin instead

Answer 11

leads to a prothrombotic state

Question 12

NPV of 4T’s score

Answer 12

100% for low score!

Question 13

When to test for HIT

Answer 13

intermediate or high probability based off of 4T’s score

Question 14

Problem with Elisa testing for HIT

Answer 14

• high false positive rate

Question 15

Elisa interpretation — what OD confirms HIT? What is indeterminate?

Answer 15

• OD less than 0.6 = negative
• OD between 0.6 and 1.9 = indeterminate
  *4T’s high probability and OD greater than 1.5 also confirms HIT
• OD greater than 2.0 = HIT confirmed
  OD = optical density

Question 16

HIPA is

Answer 16

heparin induced platelet antibody

Question 17

argatroban formulation

Answer 17

IV

Question 18

argatroban trade name

Answer 18

acova

Question 19

Fondaparinux formulation

Answer 19

PO

Question 20

Basic management of HIT once diagnosed

Answer 20

1) Stop all heparin products
2) Provide alternative anticoagulation until risk of thrombosis has been eliminated EVEN IF patients don’t have a clot for at least 4 weeks

Question 21

Parenteral anticoagulant options with HIT

Answer 21

• fondaparinux

- DTI

Question 22

What is the mechanism of fondaparinux

Answer 22

anti-thrombin dependent Xa inhibitor

Question 23

HIT vs. HITT

Answer 23

• heparin induced thrombocytopenia

- heparin induced thrombocytopenia and thrombosis