Utility of Emergency Medical Dispatch (EMD) Telephone Screening in Identifying COVID-19 Positive Patients

Background: In response to the COVID-19 pandemic, Emergency Medical Services (EMS) systems have received guidelines as part of coordinated response efforts aimed at mitigating exposures and ensuring occupational wellbeing, including recommendations of Personal Protective Equipment (PPE) utilization, and modifications of Emergency Medical Dispatch (EMD) caller queries. The aim of the study was to estimate the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of an EMD telephone screening process for the identification of hospital diagnosed COVID-19 positive patients. Methods: A retrospective cohort study was conducted of adult EMS encounters presenting to hospitals within a large health system from March 16-June 30, 2020. EMD telephone screening status was defined as either "positive" or "negative" and was collected from prehospital medical records. COVID-19 positive patients were confirmed via hospital laboratory diagnosis and were matched to their prehospital medical record data. Patient demographics and EMS encounter level data, such as Dispatch Code and Priority level, were also collected. Estimations of sensitivity, specificity, PPV and NPV were made. Emergency telephone screening status was stratified by COVID-19 diagnosis to describe discordant pairs. Results: Of the 3,443 total encounters screened, there were 652 patients who were subsequently COVID-19 positive per hospital diagnosis (18.9%). Approximately 5.0% of all encounters did not screen positive on EMD screening but were later COVID-19 positive. Conversely, 44.2% of encounters screened positive for COVID-19, but were subsequently negative. Sensitivity of the EMD telephonic screening was estimated as 75.0% (95% CI 71.7%, 78.3%) and specificity was 45.5% (95% CI 43.7%, 47.4%). The PPV was 24.3% (95% CI 22.5%, 26.0%), and NPV 88.6% (95% CI 87.0%, 90.3%). Conclusions: The sensitivity of the EMD telephonic screening process was moderately able to identify COVID-19 positive patients. There is a need to reevaluate and revise guidelines and recommendations, specifically modified caller queries, as part of ongoing pandemic emergency response efforts in order to reduce transmissions and maximize patient and provider safety.