Determination of neutrophil CD64 expression as a prognostic biomarker in patients with community-acquired pneumonia

The expression of CD64 in neutrophils (nCD64) has shown utility in the diagnosis of sepsis. The aim of this study was to assess the usefulness of nCD64 expression to identify patients with community-acquired pneumonia (CAP) at risk of a poor outcome. A prospective study of nCD64 expression (determined by flow cytometry) in patients with CAP was performed. The sensitivity/specificity of nCD64 in predicting poor outcome [defined as intensive care unit (ICU) admission and/or clinical deterioration after arrival at the emergency department] was calculated. Eighty-three adults with CAP were included; 14.5 % had septic shock, 19.3 % required ICU admission, and 10.8 % presented clinical deterioration after admission. The mean of the median fluorescence intensity (MFI) of nCD64 expression was 1140 (±1097). Patients with nCD64 expression ≥2700 MFI had more clinical deterioration (36.4 vs. 7.2 %, p = 0.015) and more ICU admission (45.5 vs. 14.5 %, p = 0.028). To identify clinical deterioration and ICU admission, nCD64 expression showed a sensitivity of 44.4 and 33.3 % and a specificity of 90.1 and 90.8 %, respectively. The addition of nCD64 expression to the Pneumonia Severity Index and CURB-65 severity scores did not improve the accuracy of predicting these outcomes. Although nCD64 expression is associated with an increased risk of ICU admission or clinical deterioration after admission, its accuracy in predicting these poor outcomes is modest and does not significantly improve the predictive ability of the PSI and CURB-65 severity scores.