Study Type – Aetiology (case series) Level of Evidence 4OBJECTIVE
To determine urinary nerve growth factor (NGF) levels in patients with overactive bladder (OAB) and after treatment with antimuscarinics.PATIENTS AND METHODS
Urinary NGF levels were measured in 38 ‘normal’ controls and 70 patients with OAB. Patients were treated with tolterodine 4 mg once daily. Urinary NGF levels were measured by enzyme-linked immunosorbent assay method and normalized by urinary creatinine levels (NGF/Cr). The urinary NGF/Cr levels and urgency severity scale (USS) were compared at baseline, 1, 2 and 3 months after antimuscarinics, and 1 month after discontinuing treatment.RESULTS
The urinary NGF/Cr level was very low in normal controls with a mean (sem) of 0.005 (0.003). Patients with OAB had significantly higher baseline urinary NGF/Cr levels than the controls. Urinary NGF/Cr levels were significantly reduced at 3 months in 50 responders (1.10 [0.26] before vs 0.41 [0.09] after, P = 0.008) but not in the 20 non-responders (1.38 [0.54] before vs 1.30 [0.46] after, P = 0.879). However, after discontinuing antimuscarinic treatment for 1 month, the urinary NGF/Cr level was elevated in 23 responders at 0.83 (0.33) and in five non-responders at 2.72 (1.41). The USS scores significantly changed with the change of urinary NGF/Cr levels in responders at different time points. The voided volume increased but maximum urinary flow rate and postvoid residual volume did not increase in responders after 3-months of antimuscarinic treatment. The limitation of this study was the lack of a control arm for comparison.CONCLUSIONS
Changes in the urinary NGF levels were associated with the changes of the USS scores after antimuscarinic treatment and discontinued medication. The urinary NGF level could be a potential biomarker for evaluating therapeutic results of antimuscarinics therapy.