New blood test predicts which Covid-19 patients will develop severe infection

Scientists have developed for the first time a scoring system that can accurately predict which hospitalised patients will develop a severe form of coronavirus.

The blood test was developed by researchers at RCSI University of Medicine and Health Sciences in Dublin and in the United States.

The measurement, called “the Dublin-Boston score”, is designed to enable clinicians to make more informed decisions when identifying patients who may benefit from therapies, such as steroids including dexamethasone, and admission to intensive care units.

Prior to this, no coronavirus-specific “prognostic scores” were available to guide clinical decision-making. The Dublin-Boston score can now accurately predict how severe the infection will be on day seven, after measuring the patient’s blood for the first four days.

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The blood test works by measuring levels of two molecules that send messages to the body’s immune system and control inflammation.

Infection

One of these molecules, interleukin (IL-6), plays a central role in the body’s defence against infection. Another form of interleukin (IL-10) has potent anti-inflammatory properties that plays a central role in limiting host immune response to pathogens, thereby preventing damage to human cells. The levels of both proteins, which are known as cytokines, are altered in severe coronavirus patients.

Based on the changes in the ratio of these two molecules over time, the researchers developed a point system “where each 1-point increase was associated with a 5.6 times increased odds for a more severe outcome”. Their findings are published in the Lancet research journal EBioMedicine.

"The Dublin-Boston score is easily calculated and can be applied to all hospitalised Covid-19 patients," said RCSI professor of medicine Gerry McElvaney, the study's lead author and a consultant at Beaumont Hospital.

“More informed prognosis could help determine when to escalate or de-escalate care, a key component of the efficient allocation of resources during the current pandemic,” he explained.

“The score may also have a role in evaluating whether new therapies designed to decrease inflammation in Covid-19 actually provide benefit.”

Limitations

The Dublin-Boston score uses the ratio of IL-6 to IL-10 because it significantly outperformed measuring the change in IL-6 alone, he said. Despite high levels in blood, IL-6 levels within the same patient vary over the course of any given day, and the magnitude of the IL-6 response to infection varies between different patients.

The Dublin-Boston score was developed with significant input from researchers in Harvard University, and the Brigham and Women's Hospital in Boston, US.

This study has inherent limitations, the researchers admit. “While the number of patients is more than three-fold larger than prior similar studies in medically-ill patients, the sample size is still small.”

They added: “More informed prognosis could help determine when to escalate care, guide clinicians seeking to institute or remove mechanical ventilation, or drive considerations for therapies. The score described here is a first step in this direction.”