What TRIage model is safest and most effective for the Management of 999 callers with suspected COVID-19? A linked outcome study (TRIM)

NHS services are experiencing highly volatile demands for care as a result of the COVID19 pandemic, with initial contact often being a 999 call to the emergency ambulance service reporting coronavirus symptoms. Triage, determining each callers' treatment, is key to appropriate care provision and resource allocation. Undertriage of 999 calls may result in avoidable serious or critical illness or death; overtriage adds unnecessary increased pressure on secondary care services, diverts resources away from the most seriously ill and may expose patients to unnecessary risk of further infection at the hospital. Little is known about what model of triage works most safely and effectively in the context of a pandemic. We will survey all ambulance services In England, Wales and Scotland to categorise triage models used in call centres and on scene during the 2020 pandemic. We will work with selected ambulance services from each triage model type and retrieve anonymised linked outcomes for callers logged by services with COVID-19 symptoms; outcomes include death, hospital and ITU admissions, Emergency Department attendances, COVID19 diagnosis. We will also track 'backwards' to examine ambulance service records of patients admitted to hospital with a diagnosis of COVID-19 in order to identify any missed or undertriaged cases. We will also undertake semi-structured interviews with stakeholders in sampled services, to gain an understanding of experiences and concerns related to implementation, effectiveness and safety. We will deliver staged outputs throughout this study in order to inform policy and practice during later stages of the current crisis and any future pandemics.