Table 3.

The “4-T” score.

Variable	Score
	0	1	2
Thrombocytopenia	< 30% decrease or nadir ≤ 10 × 103 per µl	30–50% decrease or nadir 10–19 × 103 per µl	> 50% decrease or nadir ≥ 20 × 103 per µl
Onset	< 4 days without any recent exposure to heparin	> 10 days, or < 1 day if exposure to heparin 30–100 days prior	5–10 days, or < 1 day if exposure to heparin within 30 days
Thrombosis	No	Doubtful	Yes
Alternative cause	Yes	Doubtful	No

Adapted from Lo et al. [67]. High score: 6–8, Intermediate score: 5–6, Low score: ≤ 4.