The description of a so-called cytokine storm in patients with COVID-19 has prompted consideration of anti-cytokine therapies, particularly interleukin-6 antagonists. However, direct systematic comparisons of COVID-19 with other critical illnesses associated with elevated cytokine concentrations have not been reported. In this Rapid Review, we report the results of a systematic review and meta-analysis of COVID-19 studies published or posted as preprints between Nov 1, 2019, and April 14, 2020, in which interleukin-6 concentrations in patients with severe or critical disease were recorded. 25 COVID-19 studies (n=1245 patients) were ultimately included. Comparator groups included four trials each in sepsis (n=5320), cytokine release syndrome (n=72), and acute respiratory distress syndrome unrelated to COVID-19 (n=2767). In patients with severe or critical COVID-19, the pooled mean serum interleukin-6 concentration was 36•7 pg/mL (95% CI 21•6-62•3 pg/mL; I²=57•7%). Mean interleukin-6 concentrations were nearly 100 times higher in patients with cytokine release syndrome (3110•5 pg/mL, 632•3-15 302•9 pg/mL; p<0•0001), 27 times higher in patients with sepsis (983•6 pg/mL, 550•1-1758•4 pg/mL; p<0•0001), and 12 times higher in patients with acute respiratory distress syndrome unrelated to COVID-19 (460 pg/mL, 216•3-978•7 pg/mL; p<0•0001). Our findings question the role of a cytokine storm in COVID-19-induced organ dysfunction. Many questions remain about the immune features of COVID-19 and the potential role of anti-cytokine and immune-modulating treatments in patients with the disease.

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UK Efficacy and Mechanism Evaluation Programme and National Institutes of Health.

Purpose: Using latent class analysis (LCA), we have consistently identified two distinct subphenotypes in four randomized controlled trial cohorts of ARDS. One subphenotype has hyper-inflammatory characteristics and is associated with worse clinical outcomes. Further, within 3 negative clinical trials, we observed differential treatment response by subphenotype to randomly assigned interventions. The main purpose of this study was to identify ARDS subphenotypes in a contemporary NHLBI Network trial of infection-associated ARDS (SAILS) using LCA and to test for differential treatment response to rosuvastatin therapy in the subphenotypes. Methods: LCA models were constructed using a combination of biomarker and clinical data at baseline in the SAILS study (n=745). LCA modeling was then repeated using an expanded set of clinical class-defining variables. Subphenotypes were tested for differential treatment response to rosuvastatin. Results: The 2-class LCA model best fit the population. 40% of the patients were classified as the “hyper-inflammatory” subphenotype. Including additional clinical variables in the LCA models did not identify new classes. Mortality at Day 60 and Day 90 was higher in the hyper-inflammatory subphenotype. No differences in outcome were observed between hyper-inflammatory patients randomized to rosuvastatin therapy versus placebo. Conclusions: Using LCA, a 2-subphenotype model best described the SAILS population. The subphenotypes have features consistent with those previously reported in 4 other cohorts. Addition of new class-defining variables in the LCA model did not yield additional subphenotypes. No treatment effect was observed with rosuvastatin. These findings further validate the presence of two subphenotypes and demonstrates their utility for patient stratification in ARDS.

Ventilatory Ratio correlates well with in ARDS and higher values at baseline are associated with increased risk of adverse outcomes. These results are promising for the use of Ventilatory Ratio as a simple bedside index of impaired ventilation in ARDS.