Haematology / Oncology B

HIT Expert Probability (HEP) Score

HIT Expert Probability (HEP) score (Cuker 2010): pre-test probability of heparin-induced thrombocytopenia from 8 clinical features weighted by 26 HIT experts. Better interobserver agreement than the 4Ts; use alongside anti-PF4 antibody testing.

Fall in platelet count (peak to nadir since heparin)*

Timing of the platelet fall*

Nadir platelet count*

Thrombosis (select one)*

Skin necrosis at subcutaneous heparin injection sites*

Acute systemic reaction after an intravenous heparin bolus*

Bleeding, petechiae or extensive bruising*

Other cause: chronic thrombocytopenic disorder (−1)

Yes

Other cause: newly started non-heparin drug known to cause thrombocytopenia (−2)

Yes

Other cause: severe infection (−2)

Yes

Other cause: severe DIC — fibrinogen < 1.0 g/L and D-dimer > 5.0 µg/mL (−2)

Yes

Other cause: indwelling intra-arterial device — IABP, VAD or ECMO (−2)

Yes

Other cause: cardiopulmonary bypass within the previous 96 h (−1)

Yes

No other apparent cause of thrombocytopenia (+3) — tick only if none of the above applies

Yes

Score interpretation

HEP < 2 — HIT Unlikely -16–1

HEP below 2. In the derivation study no HIT case scored below 2 (sensitivity 100%, specificity 60% at a cut-off of 2; Cuker 2010); prospective validation found lower sensitivity, so read it with the 4Ts score.

→ HIT unlikely. Investigate alternative causes of thrombocytopenia. Antibody testing usually not needed if the 4Ts score is also low.

HEP 2–4 — HIT Possible 2–4

HEP 2–4: HIT cannot be excluded (Pishko 2018: HEP ≥ 3 sensitivity 95%, specificity 36%).

→ Check anti-PF4 antibody (ELISA). Consider switching to non-heparin anticoagulant pending result. Involve haematology.

HEP ≥ 5 — HIT Likely 5–19

HEP 5 or more: sensitivity 86%, specificity 88% for HIT (Cuker 2010).

→ Stop all heparin immediately. Switch to argatroban, bivalirudin, or fondaparinux. Send PF4 antibody + confirm with serotonin release assay. Platelet transfusion generally contraindicated.

Interpretation bands for the HEP Score. Apply clinical judgement and local guidance.

References

Cuker A, et al. 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(12):2642-2650.
Pishko AM, et al. Prospective comparison of the HEP score and 4Ts score for the diagnosis of heparin-induced thrombocytopenia. Blood Adv. 2018;2(22):3155-3162.

Curated clinical cross-links plus same-class fallbacks.

Drugs

Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.

Score interpretation

References

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