|
Only one option in each category may be selected |
2 points |
1 point |
0 points |
|
Thrombocytopenia: compare the highest and lowest platelet counts to calculate % fall in platelet counts |
– >50% fall in platelet counts and nadir ≥20×109/L in patient who has not undergone surgery within prior 3 days |
– >50% fall in platelet counts and surgery within prior 3 days, or – Any other combination of platelet count fall and nadir not fulfilling other criteria |
– <30% fall in platelet counts, or – Any fall in platelet counts with nadir <10×109/L |
|
Timing of platelet count fall or thrombosis |
– Onset within 5-10 days of starting heparin, or – Onset within 1 day of starting heparin if heparin exposure within past 5-30 days |
– Unconfirmed onset within 5-10 days of starting heparin (eg, some platelet count results are lacking) – Onset within 1 day of starting heparin if heparin exposure within past 31-100 days – Onset after day 10 |
Onset of thrombocytopenia within ≤4 days with no heparin exposure (day 0 is the first day of most recent exposure to heparin) within past 100 days |
|
Thrombosis or other clinical sequelae |
– Documented new thrombosis (arterial or venous) – Skin necrosis at site of injection – Anaphylactic reaction after IV heparin administration – Adrenal hemorrhage |
– Recurrent VTE in patient treated with anticoagulants at therapeutic doses – Documented thrombosis (still to be confirmed by imaging studies) – Erythematous skin lesions at heparin injection sites |
Suspected thrombosis |
|
Other causes of thrombocytopenia not evident |
No other evident causes for platelet count fall |
Possible other causes are evident: – Sepsis with no microbiologically confirmed etiologic factor – Onset of thrombocytopenia associated with start of mechanical ventilation |
Possible other causes: – Within 72 h of surgical procedure – Documented bacteremia/fungemia – Chemotherapy or radiotherapy within prior 20 days – DIC caused by conditions other than HIT – Posttransfusion thrombocytopenia – Platelet count <20×109/L in patient who received a drug known to cause immune thrombocytopeniaa – Nonnecrotic skin lesions at LMWH injection sites (delayed hypersensitivity) |
|
Pretest probability of HIT: Score 6-8: High probability Score 4-5: Intermediate probability Score 0-3: Low probability | |||
|
a Selected agents that may cause immune thrombocytopenia: – Relatively frequently: GP IIb/IIIa antagonists (abciximab, eptifibatide, tirofiban), quinine, quinidine, sulfonamides, carbamazepine, vancomycin. – Relatively infrequently: actinomycin, amitriptyline, piperacillin, nafcillin, cephalosporins (cefazolin, ceftazidime, ceftriaxone), celecoxib, ciprofloxacin, esomeprazole, fexofenadine, fentanyl, fusidic acid, furosemide, gold salts, levofloxacin, metronidazole, naproxen, oxaliplatin, phenytoin, propranolol, propoxyphene, ranitidine, rifampin, suramin, trimethoprim. | |||
|
Adapted from J Thromb Haemost. 2010 Jul;8(7):1483-5. | |||
|
DIC, disseminated intravascular coagulation; HIT, heparin-induced thrombocytopenia; IV, intravenous; LMWH, low-molecular-weight heparin; VTE, venous thromboembolism. | |||