Simulation of Health and Economic Benefits of Extended Observation of Resolved Anaphylaxis

Marcus Shaker, Dana Wallace, David B.K. Golden, John Oppenheimer, Matthew Greenhawt

Research output: Contribution to journalArticlepeer-review


Importance: Biphasic anaphylaxis may occur in up to 20% of patients with anaphylaxis; however, the optimal observation time of patients with resolved anaphylaxis is unknown. Objective: To characterize the cost-effectiveness of short vs prolonged medical observation times after resolved anaphylaxis. Design, Setting, and Participants: An economic evaluation was performed of computer-simulated adult patients observed in outpatient allergy clinics and emergency departments, with rates of biphasic anaphylaxis derived from a 2019 meta-analysis. Exposures: Computer-simulated patients (10000 per strategy) were randomized to undergo 1 hour of medical observation (associated with 95% negative predictive value of biphasic anaphylaxis) or 6 or more hours of observation (associated with a 97.3% negative predictive value of biphasic anaphylaxis). Main Outcomes and Measures: Cost-effectiveness of 6-to 24-hour medical observation of resolved anaphylaxis evaluated at willingness-to-pay thresholds of $10000 per case of biphasic anaphylaxis observed and $10 million per death prevented, assuming that observation is associated with a 10-to 1000-fold reduction in the risk of death due to biphasic anaphylaxis. Results: Biphasic anaphylaxis occurred after hospital discharge in 365 patients observed for 1 hour and in 213 patients undergoing prolonged observation. From a health care sector perspective, with medical observation costs of $286.92 per hour, the incremental cost of extended medical observation of resolved anaphylaxis (1 hour vs 6 hours) was $62374 per case of biphasic anaphylaxis identified ($68411 from the societal perspective). In Monte Carlo simulations, with hourly costs ranging from $100 to $500 and extended observation ranging from 6 to 24 hours (health care sector perspective), the mean (SD) costs were $295.36 ($81.22) for 1 hour of observation vs $3540.42 ($1626.67) for extended observation. The incremental cost-effectiveness ratio was $213439 per biphasic anaphylaxis observed ($230202 from the societal perspective). A 6-hour observation could be cost-effective if the risk of biphasic anaphylaxis after 1-hour observation of resolved anaphylaxis was 17% or if hourly observation costs were less than $46 in the base case. Cost-effectiveness could also be achieved (willingness-to-pay of $10 million per death prevented, health care sector perspective) when a baseline fatality rate of 0.33% per biphasic anaphylactic event was assumed, with a no greater than 24% relative risk of fatality associated with 6-hour observation. Conclusions and Relevance: This study indicates that prolonged medical observation (6-24 hours) for resolved anaphylaxis may not be cost-effective for patients at low risk for biphasic anaphylaxis; however, in particular clinical circumstances of low observation costs, high postdischarge risk of biphasic anaphylaxis, or large incremental fatality risk reduction associated with extended observation, longer medical observation can be justified.

Original languageEnglish (US)
Article numbere1913951
JournalJAMA Network Open
Issue number10
StatePublished - Oct 23 2019

ASJC Scopus subject areas

  • Medicine(all)


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