Some of those who get really sick with COVID-19 develop dangerous, systemic inflammation, triggered by an overactive immune response called a cytokine storm. But predicting who will go down that path, and how to prevent it, remains a challenge.

A new Temple University study has identified a handful of chemical markers, measured with standard hospital blood tests, that may help.

The authors measured the levels of 62 such markers in hundreds of hospitalized COVID-19 patients, including proteins and other substances related to metabolism, the immune system, and other bodily functions. Just a handful were unusually elevated or suppressed in patients who went on to experience a runaway “storm” of inflammation.

Then they measured this handful of criteria in a second set of patients to see whether it would predict severe inflammatory disease. More than two-thirds of the time, it did.

In both groups, patients whose blood tests met these special criteria stayed in the hospital longer and were more likely to die, said lead author Roberto Caricchio, chief of the rheumatology section at Temple’s Katz School of Medicine.

“They are all sick people, but those that meet the criteria are, by far, sicker,” he said.

Though the severe inflammation of COVID-19 is thought to be triggered by cytokines, measuring them requires tests that are not commonly available in community hospitals. The predictive criteria identified by Caricchio and his colleagues, on the other hand, can be readily measured in a standard blood test, he said.

They include markers associated with electrolyte imbalance and tissue damage, among other warning signs. (One example is elevated levels of ferritin, a type of molecule that stores iron.) “There is nothing really special about these tests,” Caricchio said. “Any hospital with a lab could actually apply them.”

Though not a perfect predictor of severe COVID-19 disease, the Temple criteria are likely to be useful, said Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security. “Having a scoring system to help guide therapy is going to be important.”

The next step is to identify which drugs may help prevent these harmful overreactions.