Procalcitonin for diagnosis of asymptomatic bacteriuria in kidney transplant recipients

Background and aim. Asymptomatic bacteriuria (ASB) is a frequent finding in allograft kidney transplant recipients and may be associated with a higher incidence of urinary tract infections in this population. We aimed to investigate the potential utility of serum procalcitonin (PCT) concentrations, an early marker of infection, for ASB diagnosis. We also compared its diagnostic performance with white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), and highly sensitive C-reactive protein (hsCRP). Methods. In a single-center, cross-sectional study, 37 kidney transplant recipients with no clinical signs or symptoms of urinary tract infections were included. ASB was assessed by means of urine culture. Serum PCT concentrations were determined by the electrochemiluminescence immunoassay technique. Receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic performance of PCT and other classifiers. Results. Seventeen patients (46%) had ASB. Serum PCT concentrations were significantly higher in ASB+ patients (0.14 vs. 0.08 ng/ml, p=0.009). PCT concentrations significantly correlated with serum creatinine (r=0.408, p=0.012) and ESR (r=0.466, p=0.004). Of the four tested classifiers (PCT, WBC count, ESR, and hsCRP), only PCT was able to significantly distinguish between ASB+ and ASB- patients [area under the curve: 0.74, (95% CI: 057-0.91) p=0.012]. Adjustment of the ROC model for serum creatinine showed that the ability of PCT in classifying patients by ASB status is not affected by creatinine concentrations (crude vs. adjusted area under the curve: 0.74 vs. 0.72, test of AUC difference: p=0.891). A cut-point of 0.10 ng/ml of PCT correctly classified ASB+ patients with a sensitivity and specificity of 64.7% and 80.0%, respectively. Conclusion. PCT might be a useful surrogate marker for ASB diagnosis among kidney transplant recipients. Diagnostic performance of PCT is superior to that of WBC count, ESR, and hsCRP. Further, diagnostic ability of PCT appears to be independent of renal function.