@article {Goodacre88, author = {Steve Goodacre and Ben Thomas and Ellen Lee and Laura Sutton and Amanda Loban and Simon Waterhouse and Richard Simmonds and Katie Biggs and Carl Marincowitz and Jos{\'e} Schutter and Sarah Connelly and Elena Sheldon and Jamie Hall and Emma Young and Andrew Bentley and Kirsty Challen and Chris Fitzsimmons and Tim Harris and Fiona Lecky and Andrew Lee and Ian Maconochie and Darren Walter}, title = {Post-exertion oxygen saturation as a prognostic factor for adverse outcome in patients attending the emergency department with suspected COVID-19: a substudy of the PRIEST observational cohort study}, volume = {38}, number = {2}, pages = {88--93}, year = {2021}, doi = {10.1136/emermed-2020-210528}, publisher = {British Association for Accident and Emergency Medicine}, abstract = {Background Measurement of post-exertion oxygen saturation has been proposed to assess illness severity in suspected COVID-19 infection. We aimed to determine the accuracy of post-exertional oxygen saturation for predicting adverse outcome in suspected COVID-19.Methods We undertook a substudy of an observational cohort study across 70 emergency departments during the first wave of the COVID-19 pandemic in the UK. We collected data prospectively, using a standardised assessment form, and retrospectively, using hospital records, from patients with suspected COVID-19, and reviewed hospital records at 30 days for adverse outcome (death or receiving organ support). Patients with post-exertion oxygen saturation recorded were selected for this analysis. We constructed receiver-operating characteristic curves, calculated diagnostic parameters, and developed a multivariable model for predicting adverse outcome.Results We analysed data from 817 patients with post-exertion oxygen saturation recorded after excluding 54 in whom measurement appeared unfeasible. The c-statistic for post-exertion change in oxygen saturation was 0.589 (95\% CI 0.465 to 0.713), and the positive and negative likelihood ratios of a 3\% or more desaturation were, respectively, 1.78 (1.25 to 2.53) and 0.67 (0.46 to 0.98). Multivariable analysis showed that post-exertion oxygen saturation was not a significant predictor of adverse outcome when baseline clinical assessment was taken into account (p=0.368). Secondary analysis excluding patients in whom post-exertion measurement appeared inappropriate resulted in a c-statistic of 0.699 (0.581 to 0.817), likelihood ratios of 1.98 (1.26 to 3.10) and 0.61 (0.35 to 1.07), and some evidence of additional prognostic value on multivariable analysis (p=0.019).Conclusions Post-exertion oxygen saturation provides modest prognostic information in the assessment of selected patients attending the emergency department with suspected COVID-19.Trial registration number ISRCTN Registry (ISRCTN56149622) http://www.isrctn.com/ISRCTN28342533.}, issn = {1472-0205}, URL = {https://emj.bmj.com/content/38/2/88}, eprint = {https://emj.bmj.com/content/38/2/88.full.pdf}, journal = {Emergency Medicine Journal} }