Background
Pegaspargase (PEG), can cause anti-asparaginase (ASP) antibody formation, which can decrease its effectiveness without causing any clinically-apparent reaction (CAR) (silent inactivation [SI]). When a patient has SI, a switch to Erwinia  ASP is warranted, but there is currently a global shortage of Erwinia . Up to 30% of patients receiving PEG will experience a CAR, while only 8% of patients will experience SI; the only way to distinguish between these is by measuring an ASP level. However, routine ASP monitoring is not currently standard of care at all Canadian centres. This study aims to identify variations in practice regarding ASP monitoring and Erwinia  use.