Increased serum nerve growth factor levels in patients with overactive bladder syndrome refractory to antimuscarinic therapy

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.