Table 2.
Clinical characteristics of classic heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT)
| Variable | Classic HIT | VITT |
|---|---|---|
| Age | >50 Years | <55–60 Years |
| Sex | Uncertain | Male < Female |
| Incidence | 0.1%–5% of patients receiving therapeutic doses of heparin | 1:26,500–1:4,500,000 |
| History of heparin | + | None |
| Onset | ||
| Laboratory diagnosis | 5–10 days after heparin | 5–28 Days after vaccination |
| Anti-PF4/heparin antibody | Positive | Positive ELISA findings |
| Functional assay | Positive | Negative in some cases |
| Treatment | Stop heparin | IVIG |
| Non-heparin anticoagulants | Non-heparin anticoagulants | |
| Fatality | ~20% | ~20% |
| Likely due to delayed recognition of VITT |
ELISA, enzyme-linked immunosorbent assay; IVIG, intravenous immunoglobulin.