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    Original Investigation
    October 23, 2019

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

    Author Affiliations
    • 1Section of Allergy and Immunology, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
    • 2Dartmouth Geisel School of Medicine, Hanover, New Hampshire
    • 3Nova Southeastern Allopathic Medical School, Fort Lauderdale, Florida
    • 4Division of Allergy-Clinical Immunology, Johns Hopkins University, Baltimore, Maryland
    • 5Department of Internal Medicine, UMDMJ-Rutgers New Jersey Medical School, Newark
    • 6Children’s Hospital Colorado, University of Colorado School of Medicine, Section of Allergy and Immunology, Food Challenge and Research Unit, Aurora
    JAMA Netw Open. 2019;2(10):e1913951. doi:10.1001/jamanetworkopen.2019.13951
    Key Points español 中文 (chinese)

    Question  What is the cost-effectiveness of 1 hour vs 6 to 24 hours of medical observation for biphasic anaphylaxis?

    Findings  In this economic evaluation, routine use of prolonged medical observation costs $62 374 to $230 202 per case of biphasic anaphylaxis observed, depending on the hourly costs of observation and duration of stay, with costs of prolonged observation approaching or exceeding $10 million per death prevented.

    Meaning  Routine use of 6- to 24-hour medical observation for unselected patients with resolved anaphylaxis is a low-value medical practice unless the risk of biphasic anaphylaxis is significantly pronounced.


    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 (10 000 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 $10 000 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 $62 374 per case of biphasic anaphylaxis identified ($68 411 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 $213 439 per biphasic anaphylaxis observed ($230 202 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.