Prediletto I, D'Antoni L, Carbonara P, et al. - A pilot prospective observational study was conducted to observe differences between standard PaO2 over FiO2 (STP/F) and P/F in predicting outcome failure, defined as need of invasive mechanical ventilation and/or deaths in Covid-19 ARF. Researchers estimated accuracy using Receiver Operating Characteristics (ROC) analysis and areas under the ROC curve (AUROC) were compared. The study included 349 consecutive individuals who were admitted to our respiratory wards due to Covid-19 acute respiratory failure (ARF). This is the first research evaluating the role of STP/F in describing severity of ARF in Covid-19. The results showed that STP/F was found to be accurate and superior to P/F in predicting in-hospital mortality.