Table 1 |
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The 4T (thrombocytopenia, timing, thrombosis, and other causes) pretest probability of heparin-induced thrombocytopenia [6] |
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| Score |
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|
|
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| 2 |
1 |
0 |
|
|
|
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| Acute thrombocytopenia |
20 to 100 × 109/l, at least 30%, or any 50% fall |
10 to 19 × 109/l, any 30% to 50% fall, or > 50% fall post cardiac surgery |
< 10 × 109/l, or any < 30% fall |
| Timing of fall in platelet count or thrombosis or other sequalae |
Clearly 5 to 10 days (or ≤ 1 day if previous heparin given for < 30 days) |
5 to 10 days but not clear (or ≤ 1 day if previous heparin for 31 to 100 days), or
> 10 days |
≤ 4 days, with no prior heparin exposure |
| Thrombosis or other clinical sequalae |
New thrombosis, skin necrosis, or acute systemic reaction post intravenous bolus |
Progressive or recurrent thrombosis, erythematous skin lesions |
None |
| Other cause for thrombocytopenia |
No other explanation |
Possible other cause evident |
Definite other cause present |
|
|
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|
High total score, 6 to 8 (HIT very likely); intermediate total score, 4 to 5; and low total score 0 to 3. Timing = first day of exposure to heparin, counted as day 0. |
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Davenport Critical Care 2008 12:158 doi:10.1186/cc6914 |
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