Unexpected Results in New COVID-19 ‘Cytokine Storm’ Data

The immune system overactivation known as a “cytokine storm” does not play a major role in more severe COVID-19 outcomes, according to unexpected findings in new research. The findings stand in direct contrast to many previous reports.

The immune system overactivation known as a “cytokine storm” does not play a major role in more severe COVID-19 outcomes, according to unexpected findings in new research. The findings stand in direct contrast to many previous reports.

“We were indeed surprised by the results of our study,” senior study author Peter Pickkers, MD, PhD, told Medscape Medical News.

In a unique approach, Pickkers and colleagues compared cytokine levels in critically ill people with COVID-19 to those in patients with bacterial sepsis, trauma, and after cardiac arrest.

“For the first time, we measured the cytokines in different diseases using the same methods. Our results convincingly show that the circulating cytokine concentrations are not higher, but lower, compared to other diseases,” said Pickkers, who is affiliated with the Department of Intensive Care Medicine at Radboud University Medical Center in Nijmegen, the Netherlands.

The team’s research was published online on September 3 in a letter in JAMA.

Cytokines Lower Than Expected

Normally, cytokines trigger inflammation and promote healing after trauma, infection, or other conditions.

Although a cytokine storm remains ill defined, the authors note, many researchers have implicated a hyperinflammatory response involving these small proteins in the pathophysiology of COVID-19.

The question remains, however, whether all cytokine storms strike people with different conditions the same way.

Pickkers, lead author Matthijs Kox, PhD, and colleagues studied 46 people with COVID-19 and acute respiratory distress syndrome (ARDS) who were admitted to the ICU at Radboud University Medical Center. All participants underwent mechanical ventilation and were treated between March 11 and April 27, 2020.

The investigators measured plasma levels of cytokines, including tumor necrosis factor (TNF), interleukin-6 (IL-6), and interleukin-8 (IL-8). They compared results in this group to those in 51 patients who experienced septic shock and ARDS, 15 patients with septic shock without ARDS, 30 people with out-of-hospital cardiac arrest, and 62 people who experienced multiple traumas. They used historical data for the non-COVID-19 cohorts.

Conditional Findings

Compared to patients with septic shock and ARDS, the COVID-19 cohort had lower levels of TNF, IL-6, and IL-8. The differences were statistically significant for TNF (P < .01), as well as for IL-6 and IL-8 concentrations (for both, P < .001).

In addition, the COVID-19 group had significantly lower IL-6 and IL-8 concentrations compared with the patients who had septic shock without ARDS.

The researchers likewise found lower concentrations of IL-8 in patients with COVID-19 compared to the out-of-hospital cardiac arrest patients. IL-8 levels did not differ between the COVID-19 and trauma groups.