A rapid rise in C-reactive protein (CRP) levels during the first 48-72 hours of hospitalisation with Covid-19 was predictive of subsequent respiratory deterioration and intubation, according to new research.

The research published in Cell Reports Medicine also found that steadier CRP levels were observed in patients whose condition remained stable. 

Brigham and Women's Hospital researchers analysed patients' levels of CRP in 100 Covid-19 patients admitted to the hospital. They found that an increase in a cytokine called IL-6 during the first 24-48 hours was correlated to CRP levels and the progression of the disease. 

CRP tests could therefore serve as a practical addition to standard protocols for assessing the anticipated clinical trajectories of Covid-19 patients.

CRP tests provide a snapshot of a patient's inflammatory activity

Edy Yong Kim, MD, PhD, of the Division of Pulmonary and Critical Care Medicine, said: "We realised that whereas a single CRP lab value from hospital admission wasn't very practical as a predictor of who might get sicker, tracking the rate of change from Day 1 to Day 2 or 3 was a very powerful and very clinically predictive test.

"Even though all of these patients looked clinically similar upon admission, as early as 24 hours after hospitalisation, the immune systems of patients who would go on to the ICU multiple days later were already inflamed, as measured by these biomarkers."

CRP tests integrate signals from a number of different proteins involved in inflammation, called cytokines, to provide physicians with a snapshot of a patient's inflammatory activity within a matter of hours. Other tests, like cytokine assays, can provide more specific information about which proteins may be active in inflammatory pathways, but these tests can take one to two days to process, and Covid-19 patients' conditions can worsen before the results are received. 

Dr Kim added: "Doctors' and nurses' clinical instincts about Covid-19 are not fully developed because the disease is still so new. But when we showed these results to frontline doctors and nurses at the Brigham, they felt like it matched what they intuitively saw in the spring. It's always nice to hear that what you do in the lab reflects what goes on in the real world, too."