HIT Expert Probability (HEP) Score for Heparin-Induced Thrombocytopenia
Likelihood of HIT.
id
1789
full_title
HIT Expert Probability (HEP) Score for Heparin-Induced Thrombocytopenia
short_title
HIT Expert Probability (HEP) Score
med_description
Pre-test clinical scoring model for HIT based on broad expert opinion.
description
The HIT Expert Probability Score (HEP) is a clinical scoring system to stratify the pre-test probability of suspected HIT cases.
keywords
hit probability score, heparin probability, prognosis heparin, prognosis heparin calc, HIT HEP, HEP score, heparin score, expert hep score, hep thrombocytopenia score
complaint
[ "Bleeding" ]
formula
Addition of the selected points, see below:
evidence
In 50 suspected HIT patients, a literature review and expert-derived criteria of eight clinical features potentially important in the diagnosis of HIT were retrospectively applied in order to derive a HIT Expert Probability score for each patient. This score was then compared to a diagnosis of HIT by an expert panel of HIT experts. Using a cut-off of 2, the HEP score was 100% sensitive and 60% specific for the diagnosis of HIT. A cut-off of 5 yielded a sensitivity/specificity of 86%/88%, though its utility as a clinical decision tool is lessened with this cut-off. Both the HEP score and the
measurements
[]
information
| Criteria | Value | Points |
|---|---|---|
| Magnitude of fall in platelet count (peak platelet count to nadir since heparin) | a) <30% | -1 |
| b) 30-50% | +1 | |
| c) >50% | +3 | |
| Timing of fall in platelet count For patients in whom typical onset HIT is suspected |
a) Fall begins <4 days after heparin exposure | -2 |
| b) Fall begins 4 days after heparin exposure | +2 | |
| c) Fall begins 5-10 days after heparin exposure | +3 | |
| d) Fall begins 11-14 days after heparin exposure | +2 | |
| e) Fall begins >14 days after heparin exposure | -1 | |
| For patients with prior heparin exposure (last 100 days) (rapid onset HIT is suspected) |
a) Fall begins <4 days after heparin exposure | -2 |
| f) Fall begins <48 hours after heparin re-exposure | +2 | |
| g) Fall begins >48 hours after heparin re-exposure | -1 | |
| Nadir platelet count | a) ≤20 x 109/L | -2 |
| b) >20 x 109/L | +2 | |
| Thrombosis For patients in whom typical onset HIT is suspected | a) New VTE or ATE ≥4 days after heparin exposure | 3 |
| b) Progression of pre-existing VTE or ATE while receiving heparin | 2 | |
| Thrombosis for patients with prior heparin exposure (last 100 days) and rapid onset HIT is suspected | New VTE or ATE after heparin exposure | +3 |
| Progression of pre-existing VTE or ATE while receiving heparin | +2 | |
| a) Skin necrosis at subcutaneous heparin injection sites | +3 | |
| b) Acute systemic reaction after intravenous heparin bolus | +2 | |
| c) Severe DIC (fibrinogen <100 mg/dL and D-dimer >5.0 ug/mL | -2 | |
| d) Indwelling intra-arterial device (e.g. IABP, VAD, ECMO) | -2 | |
| e) Cardiopulmonary bypass within previous 96 h | -1 | |
| f) No other apparent cause | +3 | |
refrences
{ "Clinical Practice Guidelines": [], "Manufacturer Website": [], "Original/Primary Reference": [ { "href": "https://www.ncbi.nlm.nih.gov/pubmed/20854372", "text": "Cuker A, Arepally G, Crowther MA, Rice L, Datko F, Hook K, Propert KJ, Kuter DJ, Ortel TL, Konkle BA, Cines DB. The HIT Expert Probability (HEP) Score: a novel pre-test probability model for heparin-induced thrombocytopenia based on broad expert opinion. J Thromb Haemost 2010; 8: 2642–50." } ], "Other References": [], "Outcomes": [], "Validation": [ { "href": "https://www.researchgate.net/publication/260794720_External_Validation_Of_The_HIT_Expert_Probability_(HEP)_Score_a_Novel_Pre-Test_Probability_Model_For_Heparin-Induced_Thrombocytopenia_Based_On_Broad_Expert_Opinion", "text": "Lee Joseph, Gomes MPV, Al Solaiman F, St John J, Ozaki A, Raju M, Dhariwal M, Kim ESH. External Validation Of The HIT Expert Probability (HEP) Score, a Novel Pre-Test Probability Model For Heparin-Induced Thrombocytopenia Based On Broad Expert Opinion. Blood (Impact Factor: 9.06). 12/2013; 122(21):1699." } ], "Validations": [] }
pearls
The HIT Expert Probability (HEP) Score is a tool developed based on broad expert opinion to help clinicians rule out HIT.
- Eight clinical features potentially important in the diagnosis of HIT identified via literature review were incorporated into a questionnaire and distributed to independent HIT experts that regularly diagnose and treat HIT.
- Clinicians then weighed each feature on a scale of -3 to 3 with more positive numbers arguing in favor of HIT.
- Median weights were then incorporated into a pre-test probability model, the HEP score.
- Score was then prospectively applied to fifty consecutive patients referred to a single reference laboratory for HIT testing.
- HIT was diagnosed by consensus of three independent HIT expert adjudicators reviewing the clinical information and lab results including polyspecific HIT antibody ELISA and in-house SRA.
- Study found that a HEP score cut off of 2 would lead to 100% sensitivity and 60% specificity while a cut off of 5 would maximize sensitivity/specificity at 86% and 88%, respectively, in the cohort of patients analyzed. This was superior to the
4Ts for HIT Score .
Points to keep in mind:
- Validation study was very small at 50 patients, highly heterogeneous, and all done at a single large academic health care system.
- All determinations of HIT were done based on chart review.
- Score was derived based purely on expert opinion and the confirmatory diagnosis of HIT was also based on the consensus of an expert panel.
- A subsequent small (47 patients) retrospective study comparing the performance of the
4T’s scoring system vs HEP in suspected HIT patients, using a positive HPA as the gold standard for diagnosis of HIT, found no statistically significant difference in the diagnostic performance of the scores. It also demonstrated only a 70% sensitivity for the diagnosis of HIT at the previously proposed HEP score cut-off of 2. - There are no large scale or prospective studies validating the HEP score.
usecase
The heparin-induced thrombocytopenia expert probability (HEP) score is a tool that can potentially aid in diagnosing patients with suspected HIT, and to avoid expensive HIT workups in some patients.
reasons
The work-up for HIT is time-consuming and expensive. The HEP score could be used as a tool to avoid initiating work-up for HIT and/or empiric substitution of heparin for another anti-coagulant.
next_advice
next_actions
- Consider using the
4Ts scoring system in conjunction with the HEP score as an alternative evaluation tool prior to time-consuming antibody testing for HIT or empiric substitution of heparin for another anti-coagulant. - Consider further laboratory evaluation for HIT or switching to a non-heparin derived anti-coagulant in those patients that are above the screening threshold for HIT based on their HEP score.
- Larger studies of the HEP score are likely necessary prior to broader independent implementation.
next_management
diseases
[ "Thrombocytopenia" ]
instructions
published
2022-04-21T20:29:01.446Z
purpose
[ "Diagnosis" ]
search_terms
[ "hit", "plt", "platelets" ]
seo
{ "keywords_en": "hit probability score, heparin probability, prognosis heparin, prognosis heparin calc, HIT HEP, HEP score, heparin score, expert hep score, hep thrombocytopenia score", "meta_description_en": "The HIT Expert Probability Score (HEP) is a clinical scoring system to stratify the pre-test probability of suspected HIT cases." }
specialty
[ "Critical Care", "Emergency Medicine", "Hematology and Oncology", "Hospitalist Medicine", "Internal Medicine" ]
departments
[ "Hematologic" ]
tags
[]
version_number
1
versions
[]
related
[ { "calcId": 1787, "short_title_en": "4Ts for HIT", "slug": "4ts-score-heparin-induced-thrombocytopenia" }, { "calcId": 2143, "short_title_en": "Sokal Score", "slug": "sokal-index-chronic-myelogenous-leukemia-cml" }, { "calcId": 10203, "short_title_en": "ISTH Criteria for DIC", "slug": "isth-criteria-disseminated-intravascular-coagulation-dic" } ]
ismed
true
section
[ "whenToUseViewed", "pearlsPitfallsViewed", "whyUseViewed", "nextStepsViewed", "evidenceViewed" ]
cleaned_departments
[ "hematology" ]
cleaned_use
[ "The heparin-induced thrombocytopenia expert probability (HEP) score is a tool that can potentially aid in diagnosing patients with suspected HIT, and to avoid expensive HIT workups in some patients." ]
pub
true