Diagnostic and Prognostic Value of Inflammatory Parameters Including Neopterin in the Setting of Pneumonia, COPD, and Acute Exacerbations

Acute exacerbations and community-acquired pneumonia (CAP) are severe complications in patients with chronic obstructive pulmonary disease (COPD). In this study, we analyzed inflammatory parameters in serum including C-reactive protein (CRP), procalcitonin (PCT), and serum neopterin (NPT) to determine their potential to differentiate between patients with CAP+COPD and with acute exacerbations of COPD (AECOPD) without pneumonia. 102 (39 women and 63 men) patients were included in this retrospective study, of whom 48 presented with CAP without underlying COPD, 20 with CAP+COPD and 34 with AECOPD. CRP, PCT, and blood counts were determined by routine automated tests, and NPT concentrations were determined by ELISA. The ratios of CRP to NPT levels were calculated. Upon patient admission, CRP, PCT, and NPT levels were significantly higher in patients with CAP compared to those in AECOPD patients. CRP/NPT ratio was lower in AECOPD compared to CAP (+/-COPD) patients. Positive correlations were found between duration of hospitalization and CRP levels and the CRP/NPT ratio at study entry. Patients who were readmitted within 30days tended to have higher NPT levels at initial presentation. Patients under ongoing corticosteroid treatment presented with lower inflammatory parameters. The CRP/NPT-ratio was suited well to discriminate between AECOPD and CAP on the basis of COPD, a CRP/NPT cutoff of 0.346 provided a sensitivity of 65% and a specificity of 79%. The combinatory use of inflammatory patterns might help to differentiate patients with AECOPD from those with CAP on the basis of COPD.