Repeated failure to achieve adequate response to platelet transfusions, variably defined as:
- Corrected count increment (CCI) of < 5 × 109/L at 1 hour post transfusion after 2 sequential transfusions of ABO-compatible platelets, with ≥ 1 transfusion using platelets stored ≤ 48 hour.
- CCI of < 5 × 109/L/m2 at 1 hour; < 10 × 109/L at 16-24 hours.
- Platelet recovery of < 20% at 1 hour; < 10% at 16-24 hours.