The ROX index can be a useful tool for the triage evaluation of COVID-19 patients with dyspnoea

Aim To assess whether the application of a non-invasive tool, such as ratio of oxygen saturation (ROX) index, during triage can identify patients with COVID-19 at high risk of developing acute respiratory distress syndrome (ARDS). Design A multi-centre, observational, retrospective study. Methods Only COVID-19 positive patients who required an emergency department evaluation for dyspnoea were considered. The primary objective of the study was to compare the ROX value obtained during triage with the medical diagnosis of ARDS and intubation in 72 h of the triage evaluation. The ROX index value was also compared with objective outcomes, such as the pressure of arterial O-2 (PaO2)/fraction of inspired oxygen (FiO(2)) ratio and the lung parenchyma volume involved in COVID-19-related inflammatory processes, based on 3D reconstructions of chest computed tomography (CT). Results During the study period, from 20 March 2020 until 31 May 2020, a total of 273 patients with confirmed SARS-CoV-2 infection were enrolled. The predictive ability of ROX for the risk of developing ARDS in 72 h after triage evaluation was associated with an area under the receiver operating characteristic (AUROC) of 0.845 (0.797-0.892, p < 0.001), whereas the AUROC value was 0.727 (0.634-0.821, p < 0.001) for the risk of intubation. ROX values were strongly correlated with PaO2/FiO(2) values (r = 0.650, p < 0.001), decreased ROX values were associated with increased percentages of lung involvement based on 3D CT reconstruction (r = -0.371, p < 0.001). Conclusion The ROX index showed a good ability to identify triage patients at high evolutionary risk. Correlations with objective but more invasive indicators (PaO2/FiO(2) and CT) confirmed the important role of ROX in identifying COVID-19 patients with extensive pathological processes. Impact During the difficult triage evaluation of COVID-19 patients, the ROX index can help the nurse to identify the real severity of the patient. The triage systems could integrate the ROX in the rapid patient assessment to stratify patients more accurately.

Automated summary

The ROX index demonstrates a good ability to identify high-risk patients during triage, with associations with the risk of developing ARDS and requiring intubation. ROX values are correlated with PaO2/FiO2 values, and decreased ROX values are associated with increased lung involvement based on 3D CT reconstruction.