AbstractObjectiveTo assess accuracy of telephone triage in identifying patients who need emergency care amongst those with suspected COVID-19 infection and identify factors which affect triage accuracy.DesignObservational cohort studySettingCommunity telephone triage in the Yorkshire and Humber, Bassetlaw, North Lincolnshire and North East Lincolnshire region.Participants40, 261 adults who contacted NHS 111 telephone triage services provided by Yorkshire Ambulance Service NHS Trust between the 18th March 2020 and 29th June 2020 with symptoms indicating possible COVID-19 infection were linked to Office for National Statistics death registration data, hospital and general practice electronic health care data collected by NHS Digital.OutcomeAccuracy of triage disposition (self-care/non-urgent clinical assessment versus ambulance dispatch/urgent clinical assessment) was assessed in terms of death or need for organ support at 30, 7 and 3 days from first contact with the telephone triage service.ResultsCallers had a 3% (1, 200/40, 261) risk of adverse outcome. Telephone triage recommended self-care or non-urgent assessment for 60% (24, 335/40, 261), with a 1.3% (310/24, 335) risk of subsequent adverse outcome. Telephone triage had 74.2% sensitivity (95% CI: 71.6 to 76.6%) and 61.5% specificity (61% to 62%) for adverse outcomes at 30 days from first contact. Multivariable analysis suggested some co-morbidities (such as chronic respiratory disease) may be over-estimated as predictors of adverse outcome, while the association of diabetes with adverse outcome may be under-estimated. Repeat contact with the service appears to be an important under recognised predictor of adverse outcomes with both 2 contacts (OR 1.77 95% CI: 1.14 to 2.75) and 3 or more contacts (OR 4.02 95% CI: 1.68 to 9.65) associated with clinical deterioration when not provided with an ambulance or urgent clinical assessment.ConclusionPatients advised to self-care or receive non-urgent clinical assessment had a small but non-negligible risk of serious clinical deterioration. The sensitivity and specificity of telephone triage was comparable to other tools used to triage patient acuity in emergency and urgent care. Repeat contact with telephone services needs recognition as an important predictor of subsequent adverse outcomes.What is already known on this topicTelephone triage has been used to divert patients with suspected COVID-19 to self care or for non-urgent clinical assessments, and thereby help mitigate the risk of health services being overwhelmed by patients who require no speficic treatment.Concerns have been raised that telephone triage may not be sufficiently accurate in identifying need for emergency care. However, no previous evaluation of accuracy of telephone triage in patients with suspected COVID-19 infection has been completed.What this study addsPatients advised to self care or receive non-urgent clinical assessment had a small but non-negligible risk of deterioration and significant adverse outcomes.Telephone triage has comparable performance to methods used to triage patient acuity in other emergency and urgent care settings.Accuracy of triage may be improved by better recognition of multiple contact with services as a predictor of adverse outcomes.