Objective To investigate the serum nerve growth factor (NGF) and urinary NGF levels in patients with overactive bladder syndrome (OAB) refractory to antimuscarinic therapy. Materials and Methods Thirty-four patients with OAB (17 OAB-dry and 17 OAB-wet) and 31 normal subjects were enrolled. The patients were diagnosed to have OAB based on symptoms of urgency with/without urgency incontinence and 3-day voiding diary. All OAB patients had been treated with previous antimuscarinic therapy for at least 3 months but had failed. Serum and urine were collected at baseline and after solifenacin treatment for 3 months. The serum NGF and urinary NGF levels were compared between OAB-dry and OAB-wet and between baseline and after solifenacin treatment. Results Serum NGF levels were significantly elevated in OAB (median and interquartile range, 7.367 pg/ml, 0-57.66) compared to the controls (0.0728 pg/ml, 0-0.234, P <0.001). Urinary NGF/Cr levels were significantly elevated in patients with OAB (0.685 pg/mg, 0.08-1.94) compared to the controls (0.005 pg/mg, 0-0.0275, P <0.001). Serum NGF levels were significantly correlated with urinary NGF (P = 0.002) and NGF/Cr levels (P <0.001) in OAB patients. There was no significant difference of serum NGF levels between OAB-dry and OAB-wet. The serum and urinary NGF levels remained unchanged (P = 0.504 and 0.414, respectively) in OAB patients after solifenacin therapy. The serum NGF levels were highly correlated between baseline and after solifenacin treatment (R 2 = 0.83, P <0.001). Conclusions Increased serum and urinary NGF levels in patients with OAB refractory to antimuscarinic treatment suggest these bladder disorders might be caused by chronic inflammation.
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