Definite:

• Sepsis
• Cardiovascular or orthopedic surgery within 72h
• Chemotherapy in the last 20 days
• Posttransfusion purpura
• Others

Possible: 

• Thrombocytopenia associated with the initiation of ventilation
• Disseminated intravascular coagulation
• Extensive pulmonary embolism
• Thrombolytic therapy
• Drugs known to cause thrombocytopenia
• Others

No other causes apparent

• No other disease or drug present known to cause thrombocytopenia

Adapted from: 

Lo GK et al. J Thromb Haemost 2006;4(4):759–65.; Greinacher A. N Engl J Med  2015;373(3):252–61.  ; Cuker A et al. Blood Adv 2018;2(22):3360–92.; Cuker A et al. Blood 2012;120(20):4160-7.

≤ Day 4 with no recent heparin exposure:

• Occurrence of platelet count fall ≤ 4 days after initiation of heparin therapy AND
• No previous heparin exposure

> Day 10 or unclear exposure:

• Occurrence of platelet count fall > 10 days after initiation of heparin therapy OR
• Occurrence of platelet count fall < 1 day after initiation of heparin therapy and heparin exposure in the last 30-100 days

Day 5-10, or day 1 if recent heparin exposure

• Occurrence of platelet count fall on day 5-10 after initiation of heparin therapy OR
• Occurrence of platelet count fall < 1 day after initiation of heparin therapy and heparin exposure in the last 30 days

Adapted from: 

Lo GK et al. J Thromb Haemost 2006;4(4):759–65.; Greinacher A. N Engl J Med  2015;373(3):252–61. Cuker A et al. Blood Adv 2018;2(22):3360–92.; Cuker A et al. Blood 2012;120(20):4160-7.