Cuker et al reported the HIT Expert Probability (HEP) Score for evaluating a patient with heparin-induced thrombocytopenia. The authors are from the University of Pennsylvania, Duke University, McMaster University, Weill Cornell Medical College, Massachusetts General Hospital and Puget Sound Blood Center in Seattle.
Patient selection: possible heparin-induced thrombocytopenia
Parameters:
(1) magnitude of the fall in the platelet count in percent
(2) timing of the fall in the platelet count
(3) nadir platelet count
(4) thrombosis
(5) skin necrosis at subcutaneous heparin injection site
(6) acute systemic reaction after intravenous heparin bolus
(7) bleeding, petechiae or extensive bruising
(8) chronic thrombocytopenic disorder
(9) newly initiated non-heparin medication known to cause thrombocytopenia
(10) severe infection
(11) severe DIC
(12) indwelling intra-arterial device (ECMO, VAD, IABP, etc)
(13) cardiopulmonary bypass within the past 96 hours
(14) other apparent cause
|
Parameter |
Finding |
Points |
|
magnitude of fall in the platelet count |
< 30% |
-1 |
|
|
30 to 50% |
1 |
|
|
> 50% |
3 |
|
timing of the fall in the platelet count |
begins < 4 day after heparin exposure |
-2 |
|
|
begins 4 days after |
2 |
|
|
begins 5 to 10 days |
3 |
|
|
begins 11 to 14 days |
2 |
|
|
> 14 days after |
-1 |
|
|
previous exposure in last 100 days, rapid onset HIT suspected, fall starts < 48 hours after heparin exposure |
2 |
|
|
previous exposure in last 100 days, rapid onset HIT suspected, fall starts >= 48 hours after heparin exposure |
-1 |
|
nadir platelet count |
<= 20 * 10^9/L |
-2 |
|
|
> 20 ^ 10^9/L |
2 |
|
thrombosis |
new venous or arterial thrombosis >= 4 days after heparin exposure |
3 |
|
|
progression of pre-existing venous or arterial thrombosis while receiving heparin |
2 |
|
|
new thrombus after heparin exposure AND rapid HIT suspected |
3 |
|
|
progression of thrombus while receiving heparin AND rapid HIT suspected |
2 |
|
|
none of the above |
0 |
|
skin necrosis |
no |
0 |
|
|
yes |
3 |
|
acute systemic reaction |
no |
0 |
|
|
yes |
2 |
|
bleeding |
no |
0 |
|
|
yes |
-1 |
|
chronic thrombocytopenia |
no |
0 |
|
|
yes |
-1 |
|
newly initiated med |
no |
0 |
|
|
yes |
-2 |
|
severe infection |
no |
0 |
|
|
yes |
-2 |
|
severe DIC |
no |
0 |
|
|
yes |
-2 |
|
indwelling arterial device |
no |
0 |
|
|
yes |
-2 |
|
cardiopulmonary bypass |
no |
0 |
|
|
yes |
-1 |
|
no other apparent cause |
no |
0 |
|
|
yes |
3 |
where:
• The "nadir platelet count" is ambiguous. It could refer to the lowest platelet count, or the decrease from baseline to the lowest platelet count. The latter will be used in the implementation.
total score =
= SUM(points for all of the parameters)
Interpretation:
• minimum score: -16
• maximum score: 19
• A score >= 2 has a sensitivity of 100% for HIT with specificity 60%. The negative predictive value is 100%.
• A score >= 5 has a sensitivity of 86% for HIT and specificity of 88%.
Specialty: Hematology Oncology
