Table 2.
Type of VITT | UK EHP 11 | THANZ 12 |
---|---|---|
Definite VITT | All five of the following:
|
|
Probable VITT |
D‐dimer level u >4000 FEU but one criteria not met (timing, thrombosis, thrombocytopenia or anti‐PF4 antibodies) OR D‐dimer level unknown or 2000–4000 FEU and all other criteria met |
Meets platelet count, D‐dimer (and/or fibrinogen) criteria, with thrombosis but PF4 antibody negative |
Possible VITT | D‐dimer level unknown or 2000–4000 FEU with one other criterion not met, or two other criteria not met | Meets platelet count, D‐dimer (and/or fibrinogen) criteria but no thrombosis found |
Unlikely VITT |
Platelet count <150 ×109/L without thrombosis, with D‐dimer <2000 FEU OR thrombosis with platelet count >150 ×109/L and D‐dimer <2000 FEU regardless of PF4 antibody result, and alternative diagnosis more likely |
‘Less likely’ if platelet count >150 ×109/L but D‐dimer elevated or fibrinogen reduced with thrombosis ‘Much less likely’ if platelet count is stable and >150 ×109/L, D‐dimers are not elevated and fibrinogen is normal with thrombosis |