IL-6, oxygenation index tied to COVID-19 mortality risk

The oxygenation index (PaO₂/FiO₂) and interleukin (IL)-6 levels could be used to predict mortality risk among patients with the novel coronavirus disease (COVID-19), a recent study has shown.

Researchers retrospectively assessed 123 COVID-19 patients, of whom 59 were survivors and 64 had died. Logistic regression models were used to identify risk factors for mortality.

Presenting symptoms were comparable between patients who survived vs those who died, except for fatigue, which was significantly higher in the latter group (p=0.011). Heart rate (p=0.003) and respiratory rate (p=0.009) were significantly higher in those who died, while no differences in other vital signs were reported. Laboratory findings also differed between groups, including PaO2/FiO2 (p<0.0001).

Multivariable analysis confirmed that PaO₂/FiO₂ was significantly associated with the risk of mortality (odds ratio [OR], 0.96, 95 percent confidence interval [CI], 0.928–0.994; p=0.021), with an area under curve of 0.895. At a cut-off of 152.86 mm Hg, the resulting sensitivity and specificity values were 81.2 percent and 83.1 percent, respectively.

Fifty-seven patients had available IL-6 measurements, and a subgroup analysis of these patients found that IL-6 levels were indeed correlated with COVID-19 mortality risk (OR, 1.013, 95 percent CI, 1.001–1.025; p=0.028). PaO₂/FiO₂ remained significantly linked, as well (OR, 0.955, 95 percent CI, 0.915–0.996; p=0.032).

At a cut-off value of 24.24 pg/mL, the AUC of IL-6 in this subgroup was 0.9, and its sensitivity and specificity values were 95 percent and 75.68 percent, respectively. When combined, the AUC of IL-6 and PaO₂/FiO₂ was 0.936.