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Score of Warkentin and Heddle for the Diagnosis of Heparin-Induced Thrombocytopenia (HIT)

Purpose: To evaluate a patient for heparin-induced thrombocytopenia (HIT) using the diagnostic score of Warkentin and Heddle.

Description

Warkentin and Heddle developed a score for the diagnosis of immune heparin-induced thrombocytopenia (HIT). This can help distinguish HIT from conditions that have similar features. The authors are from Hamilton Health Sciences in Ontario, Canada.


Parameters:

(1) platelet count

(2) timing of onset after starting heparin therapy

(3) thrombosis

(4) other causes

 

decrease in platelet count in percent =

= ((platelet count before) - (platelet count after)) / (platelet count before) * 100%

 

Parameter

Finding

Points

platelet count

< 30% drop OR absolute count < 10,000 per µL

0

 

30 - 50% drop OR absolute count 10,000 - 19,000 per µL

1

 

> 50% drop OR absolute count 20,000 - 100,000 per µL

2

timing of onset after starting heparin

< 5 days without a recent exposure to heparin

0

 

> 10 days after starting heparin

1

 

5 to 10 days after starting heparin

2

 

< 1 day with a recent exposure to heparin

2

thrombosis

none

0

 

recurrent or progression in thrombus; suspect thrombosis; skin erythema

1

 

new onset of thrombosis; skin necrosis; acute systemic reaction

2

other causes

definite

0

 

possible

1

 

none

2

 

where:

• The "absolute count" under platelet count refers to the drop in the platelet count from baseline.

 

total score =

= SUM(points for all 4 parameters)

 

Interpretation:

• minimum score: 0

• maximum score: 8

• The higher the score the more likely HIT is present.

 

Total Score

Probability of HIT

<= 3

low

4 or 5

intermediate

>= 6

high

 


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Specialty

Objective

ICD-10