Screening and Diagnosis Screening
ÎFor patients receiving heparin in whom clinicians consider the risk of HIT to be > 1%, the ACCP suggests monitoring platelet counts every 2-3 days from days 4-14 (or until heparin is stopped, whichever occurs first). (2C)
ÎFor patients receiving heparin in whom clinicians consider the risk of HIT to be < 1%, the ACCP suggests platelet counts need not be monitored. (2C)
ÎMonitor platelet count in patients recently treated with heparin/LMWH.
ÎMonitor platelet count in patients with acute inflammatory reactions after an IV heparin bolus. Diagnosis
ÎThe best studied clinical prediction tool to assist physicians with determining the probability that a patient has HIT is the 4Ts score. Patients with a low 4Ts score have a very low probability of HIT (0%-3%). However, many patients (24%-61%) with a high 4Ts score prove not to have HIT.
Table 2. 4Ts Scorea Score = 2
Thrombocytopenia
Compare the highest platelet count within the sequence of declining platelet counts with the lowest count to determine the percent of platelet fall. (Select only 1 option)
> > 50% platelet fall AND a nadir of ≥ 20 x 109
AND no surgery within preceding 3 days
/L
> > 50% platelet fall BUT surgery within preceding 3 days OR
> < 30% platelet fall > Any platelet fall
> Any combination of platelet fall and nadir that does not fit criteria for Score 2 or Score 0 (eg, 30-50% platelet fall or nadir 10-19 x 109
/L) Timing (of platelet count fall or thrombosisb
Day 0 = first day of most recent heparin exposure (Select only 1 option)
> Platelet fall day 5-10 after start of heparin
> Platelet fall within 1 day of start of heparin AND exposure to heparin within past 5-30 days
)
> Consistent with platelet fall day 5-10 but not clear (eg, missing counts)
> Platelet fall within 1 day or start of heparin AND exposure to heparin in past 31-100 days
> Platelet fall after day 10
> Platelet fall on or before day 4 without exposure to heparin in past 100 days
with nadir < 10 x 109
/L Score = 1 Score = 0
