Urinary brain-derived neurotrophic factor: a potential biomarker for objective diagnosis of overactive bladder.

Purpose: To investigate the diagnostic performance of urinary brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) as potential biomarkers for overactive bladder (OAB).

Methods: Ninety women diagnosed with OAB and 45 normal controls without OAB were enrolled. Urine samples were collected from all subjects. Urinary BDNF and NGF levels were measured using enzyme-linked immunosorbent assays. Results normalized by urinary creatinine (Cr) levels were compared between OAB groups and controls. Symptom severity was assessed using overactive bladder symptom score.

Results: Urinary BDNF and NGF levels were elevated in OAB groups but not in controls. Mean (SD) baseline BDNF and NGF levels normalized by Cr levels were significantly higher in OAB subjects than in controls (20.609 ± 23.932 vs. 1.779 ± 0.729, p < 0.01) and (0.258 ± 0.264 vs. 0.081 ± 0.028, p < 0.01), respectively. Urinary BDNF/Cr levels were 80-fold higher than NGF/Cr levels in OAB subjects. Receiver operating characteristic curves for assessing urinary BDNF/Cr levels in OAB groups showed sensitivity and specificity of 93.33 and 88.89 %, respectively. Urinary BDNF levels were associated with OAB symptom severity.

Conclusions: Urinary BDNF/Cr levels are elevated in women with OAB and are significantly associated with symptom severity. No elevation of BDNF is found in women without OAB. BDNF analysis has better sensitivity than NGF in detecting OAB in subjects without other lower urinary tract disorders. Results of the present study suggest a potential role for BDNF as an objective biomarker for OAB diagnosis.