Utility of copeptin and standard inflammatory markers in the diagnostics of upper and lower urinary tract infections

BACKGROUND A new serum marker of inflammation copeptin (CPP) a stable C-terminal pro-vasopressin was assessed along with conventional markers such as C-reactive protein (CRP), procalcitonin (PCT) and IL-6 to discriminate between lower and upper bacterial urinary tract infections (UTI). METHODS Study population comprised 45 patients including 13 with lower UTI (L-UTI) and 32 with upper UTI (U-UTI) and 24 healthy controls. Serum markers, blood cultures and urine cultures were assessed before commencing antibiotic treatment and repeated 24, 48 h and 7 days thereafter. Receiver operating curves (ROC) were plotted to assess a diagnostic utility of different inflammatory markers. RESULTS Before antibiotic therapy all inflammatory markers including serum CPP (2821.1 ± 1072.4 pg/ml vs. 223.8 ± 109.3 pg/ml; p < 0.05) were higher in UTI than in controls. CPP was not different between L- and U-UTI (2253 ± 1323 pg/ml vs 3051 ± 1178 pg/ml; p = 0.70) despite significant differences in hsCRP (2.09 ± 1.7 mg/dl vs 127.3 ± 62.4 mg/dl; p < 0.001), PCT (0.05 ± 0 vs 5.02 ± 0.03 ng/ml p < 0.001) and IL-6 (22.5 ± 1.6 vs 84.8 ± 67 pg/ml p < 0.001). For U-UTI the areas under the ROC curves were 1.0 for both hsCRP and CPP, 0.94 for PCT and 0.7 for IL-6 and for L-UTI 0.571, 1, 0.505 and 0.73, respectively. After 7 days of treatment all markers decreased in parallel to clinical response. CONCLUSION Although elevated serum copeptin may become a marker of UTI it seems to be inferior compared to traditional serum inflammation markers for differentiation of bacterial infections involving upper and lower urinary tract.