To assess the cost-effectiveness of an evidence-informed institutional protocol for physicians that encouraged management of children with newly diagnosed immune thrombocytopenia (ITP) with observation over active therapy, where appropriate.

We conducted a probabilistic cost-effectiveness analysis from an institutional perspective using a decision tree with a 1 year time horizon. Patient-level data were retrospectively ascertained for children diagnosed in pre-protocol (2007-2009) and post-protocol (2013-2018) time periods. ITP resolution was defined as achieving a sustained platelet count of >100 × 10³/μL at 9-12 months after diagnosis. Outpatient care and inpatient costs were obtained from the institution and provincial sources. Intervention costs accounted for quality improvement initiative preparation and staff physician training. Incremental costs, incremental effects, and CIs were calculated from 10 000 model iterations.

Forty-eight patients were followed for 1 year in the pre-protocol period and 84 in the post-protocol period. After protocol implementation, an average cost savings per child managed of $2055 (95% CI: $656, $3890) Canadian Dollars was observed, as was a higher proportion of resolved ITP cases. The implementation strategy remained less costly and more effective in 99.7% of model iterations.

Implementation of an evidence-informed institutional protocol to guide physicians toward increased uptake of observation over active therapy when managing children with newly diagnosed ITP resulted in significant cost savings on a per case basis, even after accounting for training-related costs. Though the long-term cost implications regarding the sustainability of the intervention are not yet known, it is anticipated that continued institutional savings could occur.