Blood levels of two specific proteins, IL-6 and IL-10, can be discriminative biomarkers of the severity of pneumonia in children, and may help doctors when adjusting treatment in severe cases, a study in the journal BMC Pulmonary Medicine reports.
The clinical severity of pneumonia arises from the interaction of several factors, including the environment, characteristics of the infectious agent, and anemia. Usually, it is determined by blood cell counts and serum levels of the C-reactive protein (CRP; an indicator of inflammation), which shape the therapeutic approach. But these are not specific markers for pneumonia.
Recent studies have shown that blood and pulmonary levels of proteins called cytokines could be related to the severity of the pulmonary inflammatory process, by either inducing or inhibiting inflammation. Some studies, however, reported conflicting results regarding cytokine involvement in the inflammatory process during acute respiratory disease.
Researchers in this study, “The balance between the serum levels of IL-6 and IL-10 cytokines discriminates mild and severe acute pneumonia,” aimed to identify markers for earlier diagnosis of severe pneumonia. To do so, they assessed blood levels of specific cytokines and correlated these with pneumonia severity, defined by clinical manifestations and alterations in blood count, in children and adolescents.
Twenty-five hospitalized children were enrolled in the study, seven with mild and 18 with severe pneumonia. Blood levels of 11 different cytokines were measured at three sampling times.
Researchers reported that, at diagnosis, the levels of the cytokine IL-10 were lower, and those of the cytokine IL-6 higher, in children with severe pneumonia when compared to levels in children with milder cases.
IL-6 blood levels were also associated with vomiting in both severe and non-severe pneumonia patients, and — in severe cases only — with dyspnea (shortness of breath) and white blood cell counts. This suggests that IL-6 plays a role in pneumonia severity. IL-10 levels were associated with an increased number of immune cells called lymphocytes in the blood of both groups.
Interestingly, researchers found that IL-6 levels equal to or higher than 21.1 pg/mL, and an IL-6 to IL-10 ratio of at least 9.61, could discriminate severe pneumonia from mild disease with high sensitivity (76.5%), and predictive value (93%).
During recovery, the major difference found between pneumonia and severe pneumonia patients was a reduction in the levels of IL-6, but no major alteration in the levels of IL-10.
Importantly, on the third day of antibiotics therapy — when patients’ clinical condition is usually evaluated for possible changes in treatment protocol — an IL-6 to IL-10 ratio higher than 5.0 correlated with a persistence of symptoms. This finding indicates the ratio may serve as a predictive pneumonia biomarker, helping in medical decisions on adjusting treatment for severe cases.
Overall, results showed that the IL-6 to IL-10 ratio of blood levels could be important in defining pneumonia severity at hospital admission, and a predictive tool for therapy adjustment.
“In future, the determination of IL-6 and IL-10 serum levels may be offered by routine laboratory as one more marker to evaluate the severity of infection disease at the diagnosis,” the researchers concluded.