Inter-rater reliability and prognostic value of baseline Radiographic Assessment of Lung Edema (RALE) scores in observational cohort studies of inpatients with COVID-19
Authors: Al-Yousif Nameer , Komanduri Saketram , Qurashi Hafiz , Korzhuk Anatoliy , Lawal Halimat O , Abourizk Nicholas , Schaefer Caitlin , Mitchell Kevin J , Dietz Catherine M , Hughes Ellen K , Brandt Clara S , Fitzgerald Georgia M , Joyce Robin , Chaudhry Asmaa S , Kotok Daniel , Rivera Jose D , Kim Andrew I , Shettigar Shruti , Lavina Allen , Girard Christine E , Gillenwater Samantha R , Hadeh Anas , Bain William , Shah Faraaz A , Bittner Matthew , Lu Michael , Prendergast Niall , Evankovich John , Golubykh Konstantin , Ramesh Navitha , Jacobs Jana J , Kessinger Cathy , Methe Barbara , Lee Janet S , Morris Alison , McVerry Bryan J , Kitsios Georgios D 
Published: January 2023

ObjectivesTo reliably quantify the radiographic severity of COVID-19 pneumonia with the Radiographic Assessment of Lung Edema (RALE) score on clinical chest X-rays among inpatients and examine the prognostic value of baseline RALE scores on COVID-19 clinical outcomes.SettingHospitalised patients with COVID-19 in dedicated wards and intensive care units from two different hospital systems.Participants425 patients with COVID-19 in a discovery data set and 415 patients in a validation data set.Primary and secondary outcomesWe measured inter-rater reliability for RALE score annotations by different reviewers and examined for associations of consensus RALE scores with the level of respiratory support, demographics, physiologic variables, applied therapies, plasma host–response biomarkers, SARS-CoV-2 RNA load and clinical outcomes.ResultsInter-rater agreement for RALE scores improved from fair to excellent following reviewer training and feedback (intraclass correlation coefficient of 0.85 vs 0.93, respectively). In the discovery cohort, the required level of respiratory support at the time of CXR acquisition (supplemental oxygen or non-invasive ventilation (n=178); invasive-mechanical ventilation (n=234), extracorporeal membrane oxygenation (n=13)) was significantly associated with RALE scores (median (IQR): 20.0 (14.1–26.7), 26.0 (20.5–34.0) and 44.5 (34.5–48.0), respectively, p<0.0001). Among invasively ventilated patients, RALE scores were significantly associated with worse respiratory mechanics (plateau and driving pressure) and gas exchange metrics (PaO2/FiO2 and ventilatory ratio), as well as higher plasma levels of IL-6, soluble receptor of advanced glycation end-products and soluble tumour necrosis factor receptor 1 (p<0.05). RALE scores were independently associated with 90-day survival in a multivariate Cox proportional hazards model (adjusted HR 1.04 (1.02–1.07), p=0.002). We replicated the significant associations of RALE scores with baseline disease severity and mortality in the independent validation data set.ConclusionsWith a reproducible method to measure radiographic severity in COVID-19, we found significant associations with clinical and physiologic severity, host inflammation and clinical outcomes. The incorporation of radiographic severity assessments in clinical decision-making may provide important guidance for prognostication and treatment allocation in COVID-19.