Urinary nerve growth factor levels are elevated in patients with overactive bladder and do not significantly increase with bladder distention

Abstract

Urinary nerve growth factor (NGF) levels have been found to be higher in patients with overactive bladder (OAB) compared to normal controls. This study investigated the effect of bladder volume on urinary NGF production in normal controls and patients with OAB. Urinary NGF levels were measured in 39 patients with OAB and in 35 control subjects without lower urinary tract symptoms (LUTS). Urine samples were collected at the first sensation of bladder filling (FSF) and at urge sensation (US), respectively, in both groups. Measurement of urinary NGF levels was performed by ELISA method and normalized by urinary creatinine concentration (NGF/Cr). The correlation between NGF/Cr level and increased bladder volume was analyzed. Urinary NGF/Cr levels in normal controls were very low at FSF (mean +/- standard error, 0.011 +/- 0.008) and were significantly higher at US (0.086 +/- 0.022, P = 0.005). Patients with OAB had significantly higher urinary NGF/Cr levels both at FSF (0.45 +/- 0.13, P = 0.001) and US (1.00 +/- 0.32, P = 0.004) compared to controls. The difference in urinary NGF/Cr levels between FSF and US in OAB patients, however, was not significant (P = 0.064). Urinary NGF/Cr level was well correlated with bladder volume at US in the controls but not significant associated with bladder volume increase in patients with OAB. The results of this study suggest urinary NGF increases physiologically in normal subjects at urge to void but is pathologically elevated in OAB patients at small bladder volume and does not significantly increase at urgency sensation.