VITT-adapted 4Ts scoring system

Parameter	Point(s)
Thrombocytopenia
Platelet count 10,000 to 99,000/microL	2
Platelet count <10,000/microL or 100,000 to 149,000/microL	1
Platelet count ≥150,000/microL	0
Timing*
5 to 14 days post vaccine	2
15 to 30 days post vaccine	1
0 to 4 days or ≥30 days post vaccine	0
Thrombosis
Definite thrombosis or D-dimer >10 mg/L (>10,000 ng/mL)	2
Suspected (not documented) thrombosis or D-dimer 2.00 to 9.99 mg/L (2000 to 9990 ng/mL)	1
No thrombosis and D-dimer <2 mg/L (<2000 ng/mL)	0
Other cause of thrombosis or thrombocytopenia
None apparent	2
Possible	1
Definite	0
Interpretation	Total
0 to 3 points – Low probability
4 to 5 points – Intermediate probability
6 to 8 points – High probability

This table is adapted from the 4Ts score for HIT, which has been validated in various populations. This adapted scoring system has not been validated, and the incidence of VITT is very low, making validation challenging. As a result, the interpretations do not carry a specific risk for VITT or correlate with a specific likelihood of positive PF4 antibody testing.

VITT: vaccine-induced immune thrombotic thrombocytopenia; HIT: heparin-induced thrombocytopenia.
* The day of vaccination is considered day 0; refer to UpToDate for details of implicated vaccines.

Graphic 131493 Version 1.0

خرید پکیج

VITT-adapted 4Ts scoring system