Determining the risk of developing symptomatic covid-19 infection after attending hospital for radiological examinations: controlled cohort study

OBJECTIVE To determine whether brief attendance for outpatient radiological investigations is associated with increased risk of clinically significant coronavirus disease 2019 (covid19) infection. DESIGN Observational cohort study with a historical control. SETTING 2 large UK University Hospitals located in Nottingham and Cardiff. PARTICIPANTS All 47,340 patients who attended an outpatient radiology appointment at Nottingham University Hospitals and University Hospital of Wales during the first wave of the pandemic in 2020, and 70,655 patients that comprised the control cohort who attended for outpatient radiology the same period in 2019. MAIN OUTCOME MEASURES The risk of developing clinically significant covid-19 infection within 28 days of attending a radiological examination. Covid19 infection rates for the 2020 cohort were compared against a control group who attended in 2019. RESULTS 84 positive SARSCoV2 tests were temporally associated with 47,340 radiological examinations across two hospitals in 2020. This low infection rate was higher than the 2019 control cohort; OR 2.507 (1.766 3.559) and equates to an approximate 1 positive covid19 infection per 1000 radiology investigations. CONCLUSIONS Our data suggests that attending hospitals for outpatient radiological investigations during the pandemic is associated with a very small absolute risk of acquiring clinically significant covid19 infection. It is unlikely that this risk is directly attributable to radiology attendance, considering the reasons leading individuals to attend hospitals during the pandemic, the true attributable risk will likely be even lower. TRIAL REGISTRATION ClinicalTrials.gov NCT04544176