AbstractBackgroundA cross‐sectional nationwide study was designed to assess national compliance with international consensus/guidelines of monitoring asparaginase levels in children with acute lymphoblastic leukemia (ALL) treated with asparaginase in routine clinical practice.MethodsAn ad hoc questionnaire was designed and completed by staff physicians from Hemato‐Oncology Units throughout Spain.ResultsA total of 39 physicians (64% pediatricians) with a mean (SD) age 43.5 (7.9) years and 15.3 (17.6) years of professional activity participated in the study. They accounted for 90% of hospitals in which children with ALL are treated in Spain. A total of 19 participants (48.7%) reported that asparaginase levels were routinely monitored (own center in 2 cases [10.5%], another hospital in 17 cases [89.5%]). Asparaginase was not monitored in 51.3% of the cases, mostly (80%) because unavailability of testing. When asparaginase was monitored, 68% of participants reported that this was done in all asparaginase‐treated patients and 84% in all phases of the disease (induction, consolidation, re‐induction, maintenance) with a time interval of 7 days for the pegylated form, 48 h for Erwinia asparaginase and 14 days for maintenance with the pegylated form. All participants reported that they modified treatment according to results of testing, with a limit of total depletion of ≥100 IU/L. Levels <100 or 20 IU/L were considered indicative of hypersensitivity by 46% of physicians.ConclusionThere is still a gap between what is recommended and what is done in clinical practice, with more than 50% of centers not monitoring the level of asparaginase activity in pediatric ALL. Protocols for asparaginase testing in daily practice should be implemented.