Plasma levels of soluble Axl correlate with severity of community-acquired pneumonia

The aim of this study was to examine the plasma level changes of soluble Axl (sAxl) prior to and following treatment with antibiotics in hospitalized adult patients with community-acquired pneumonia (CAP), and to investigate the correlating clinical and laboratory manifestations of CAP with plasma sAxl levels. Blood samples were obtained from 61 adult CAP patients (prior to and following treatment with antibiotics) and 60 healthy controls in order to measure the plasma concentrations of sAxl using the enzyme-linked immunosorbent assay. The plasma-soluble Axl concentration level was markedly elevated in patients with CAP prior to treatment, compared with the controls, and decreased markedly following treatment. The levels of white blood cells, neutrophils, and C-reactive protein decreased markedly following treatment with antibiotics and did not correlate with the concentration level of sAxl. However, the plasma concentration of sAxl correlated with the severity of CAP with the pneumonia severity index score (r=0.350, P=0.006, n=61), the CURB-65 score (r=0.281, P=0.028, n=61) and the acute physiology and chronic health evaluation II score (r=0.313, P=0.014, n=61). In conclusion, plasma sAxl may be involved in the clinical assessment of the severity of CAP, which may guide the development of treatment strategies and predict the clinical outcome.