Age, PaO2:FiO2 ratio simple predictors of prognosis in hospitalized COVID-19 patients

The performance of prognostic models for COVID-19 is modest, but simple predictors like age and the ratio of arterial partial pressure of oxygen to fraction of inspired oxygen may useful as stand-alone predictors, researchers reported.

“Our study shows that currently available prognostic models recommended for risk stratification in different [settings] of critically ill patients ... have modest performance in assessing mortality and risk of critical illness in hospitalized patients with COVID-19,” Maria Cristina Vedovati, MD, from the internal, vascular and emergency medicine-stroke unit at the University of Perugia in Italy, and colleagues wrote in Respiratory Medicine.

The study included 1,044 consecutive patients with acute confirmed COVID-19 pneumonia (mean age, 68.3 years; 62.1% men) who were hospitalized at five non-ICU centers in Italy in 2020 during the COVID-19 pandemic. Researchers calculated 12 validated prognostic scores for pneumonia and/or sepsis and specific COVID-19 scores for each patient. The accuracy of these scores was compared for predicting in-hospital mortality within 30 days and the composite outcome of death and orotracheal intubation.

Overall, 28.9% of patients presented with clinical illness and 21.6% died during the hospital stay (mean stay, 15.5 days).

Only nine of the 34 items included in various prognostic scores were independent predictors of all-cause mortality, according to the researchers.

The following were identified as independent predictors of in-hospital mortality:

• age 60 years and older (HR = 4.13; 95% CI, 1.49-11.43);
• presence of at least two comorbidities (HR = 2.43; 95% CI, 1.57-3.76);
• Glasgow coma scale lower than 15 (HR = 1.94; 95% CI, 1.07-3.54);
• mean blood pressure lower than 70 mm Hg (HR = 4.19; 95% CI, 1.5-11.71);
• respiratory rate higher than 20 bpm (HR = 1.58; 95% CI, 1-2.5);
• arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2:FiO2) ratio lower than 200 mm Hg (HR = 1.88; 95% CI, 1.22-2.89);
• PaO2 lower than 60 mm Hg (HR = 1.6; 95% CI, 1.05-2.45);
• oxygen saturation lower than 90% (HR = 1.73; 95% CI, 1.12-2.69); and
• respiratory index of 3.8 or lower (HR = 1.82; 95% CI, 1.19-2.8).

Researchers observed acceptable discrimination for most scores predicting in-hospital mortality within 30 days, including APACHE II, COVID-GRAM, Rapid Emergency Medicine Score (REMS), CURB-65, NEWS II, ratio of oxygen saturation index (ROX index), 4C and SOFA. They reported a high negative predictive value of 100% for the REMS score and 98.7% for the 4C scores. The positive predictive value of these scores was poor, the researchers wrote. The best positive predictive value overall was the ROX index (75%).

“[A] better understanding of determinants of prognosis could improve clinical management and also resources allocation for current COVID-19 patients and for potential new COVID-19 waves,” the researchers wrote. “These data can certainly serve to implement the management of non-COVID-related acute respiratory distress syndromes.”