Urine and Serum C-Reactive Protein Levels as Potential Biomarkers of Lower Urinary Tract Symptoms

Objective The association of elevated serum C-reactive protein (CRP) with lower urinary tract symptoms (LUTS) suggests a possible role of inflammation. We investigated whether measurement of urine CRP levels can complement the deficit in the specificity of serum CRP levels as potential biomarkers of lower urinary tract inflammation. Patients and Methods Serum CRP levels were measured in 97 patients with LUTS; urinary CRP was additionally measured in 20 of the patients. Bladder expression of CRP was quantified by real-time polymerase chain reaction on human bladder t issue obtained from 15 organ donors. Results Significantly higher serum CRP levels were noted in overactive bladder (OAB) wet (n = 18; 2.96 ± 0.47 mg/L), chronic prostatitis (n = 5; 3.00 ± 1.05 mg/L), benign prostatic hyperplasia (n = 20; 1.13 ± 0.17 mg/L), and acute febrile bacterial infection (n = 5; 97.71 ± 36.28 mg/L) compared to in asymptomatic controls (n = 20; 0.93 ± 0.27 mg/L). Serum CRP level was higher in OAB wet than in OAB dry (n = 20). Urinary CRP level was higher than 0.15 mg/L in only one man with bacterial prostatitis and sepsis. The mRNA expression of CRP was very modest and several fold lower than the expression of housekeeping genes in the detrusor or urothelium. Conclusion Serum CRP was elevated with different disease entities in patients with LUTS. The synthesis of CRP is unlikely in the bladder and the protein is not a normal urine constituent. This pilot study has led us to infer that urinary CRP is unlikely to serve as a biomarker of LUTS. Sensitive but nonspecific elevation of serum CRP level suggests an inflammatory mechanism with LUTS.