Urinary nerve growth factor levels in overactive bladder syndrome and lower urinary tract disorders

Overactive bladder (OAB) is a syndrome based on self-reported symptoms of urgency and frequency with or without urge incontinence. Although urgency is the core symptom of OAB, patients might have difficulty to distinguish urgency from the urge to void. Urodynamic study is a useful diagnostic tool to discover detrusor overactivity (DO) in patients with OAB; however, not all OAB patients have DO. Therefore, a more objective and non-invasive way to diagnose and assess OAB including DO is needed. Recent research has focused on urinary biomarkers in assessment of OAB. Urinary nerve growth factor (NGF) level increases in patients with OAB-wet, bladder outlet obstruction, mixed urinary incontinence and urodynamic DO. Urinary NGF levels are correlated with severity of OAB symptoms. In patients with OAB and DO who have been well treated with antimuscarinics or botulinum toxin injection, urinary NGF levels have been shown to decrease significantly in association with reduction of urgency severity. However, not all patients with OAB have an elevated urinary NGF level. It might also be increased in patients with interstitial cystitis/painful bladder syndrome, cerebrovascular accident and lower urinary tract diseases such as urinary tract stone, bacterial infection and urothelial tumor. It is possible to use urinary NGF levels as a bio-marker for diagnosis of OAB as well as for the assessment of therapeutic outcome in patients with OAB or DO. Here, we review the latest medical advances in this field.