A recent study conducted by Humanitas researchers on patients hospitalized for Covid-19 shows that the level of PTX3 in the blood allows for the early diagnosis of potential secondary co-infections and helps predict their course, optimizing therapies

Pentraxin 3 (PTX3) is a key protein in the inflammatory response, discovered by Alberto Mantovani’s group in the early 2000s. Thanks to data collected during the Covid-19 pandemic, a group of researchers led by Professor Cecilia Garlanda, head of the Experimental Immunopathology Laboratory at Humanitas and associate professor at Humanitas University, has now shown that this protein serves as a diagnostic and predictive biomarker for secondary infections.

The study, published in eBioMedicine, highlights how PTX3 outperforms traditional clinical biomarkers such as C-reactive protein (CRP) and procalcitonin (PCT) in precision and predictive power. If further confirmed in future prospective studies, the results could pave the way for its clinical implementation.

The study was made possible through the collaboration between Humanitas research scientists and the doctors of the Infectious Diseases Unit – in particular, Enrico Brunetta and Federica Tordato – and was supported by funds donated by Dolce & Gabbana.

The Study

The study involved 280 hospitalized COVID-19 patients: 101 with secondary bacterial or fungal infections and 179 without secondary infections, forming the control group. The researchers measured the plasma levels of PTX3 and compared them with those of CRP and PCT, the two biomarkers routinely used in clinical settings.

“The analyses showed that PTX3 level is significantly higher in patients with co-infections compared to those without secondary infections and is able to identify the presence of co-infections with greater precision than the markers already in use,” explain Enrico Brunetta and Francesco Scavello, a researcher at the laboratory directed by Professor Garlanda and the first author of the study. “Furthermore, PTX3 is confirmed as an independent predictor of 28 days’ mortality and ICU admission in Covid-19 patients, thus representing an effective tool for risk stratification and targeted patient management.”

The Diagnostic Potential of PTX3

The implications of the study go beyond Covid-19 because PTX3 is a fundamental molecule of the innate immune response – it is at the origin of the chain of inflammatory signals that guide the immune response in the early stages of infection. It is reasonable to hypothesize that PTX3 is also an effective marker in other conditions where a fragile patient is hospitalized for a viral infection and there is suspicion of a secondary infection, often arising in the hospital setting.

“These results suggest that the introduction of PTX3 in clinical practice would improve the management of patients with severe infections by identifying secondary infections early and improving therapeutic outcomes,” says Professor Garlanda. “Using PTX3 in clinical practice would also help reduce the unnecessary use of antibiotics, which today are often administered preventively in fragile patients with pneumonia even without evidence of co-infections. This is particularly relevant in a context where antimicrobial resistance represents one of the main threats to global health.”