Objective: To measure urinary nerve growth factor (NGF) levels in patients with interstitial cystitis/bladder pain syndrome (IC/BPS), and to evaluate the role of urinary NGF in predicting the response to treatment, as the clinical diagnosis of IC/BPS is based on subjective symptoms and recent investigations suggest that urinary NGF is increased in patients with IC/BPS.
Patients, subjects and methods: Urine samples from 122 patients with IC/BPS and 28 normal controls were measured for NGF levels using an enzyme-linked immunosorbent assay. The diagnosis of IC/BPS was based on bladder pain symptoms and the results of cystoscopic hydrodistension. Patients' perception of pain was assessed by a visual analogue scale (VAS) and a 'global' response assessment after treatment. Urinary NGF levels were further normalized to the concentration of urinary creatinine (NGF/Cr) and compared between control and IC/BPS subgroups at diagnosis and after treatment.
Results: Urinary NGF/Cr levels were very low when the bladder was not distended and significantly elevated with a full bladder in patients with IC/BPS. However, urinary NGF/Cr levels were not correlated with VAS scores or cystometric bladder capacity at diagnosis, or maximum bladder capacity during hydrodistension. Patients who responded to treatment and had an improvement in VAS pain score of > or =2 had significantly lower NGF/Cr levels than nonresponders who had a VAS improvement of <2.
Conclusions: Patients with IC/BPS had greater urinary NGF/Cr levels than controls. A decrease of urinary NGF level was associated with greater pain reduction and a successful response, suggesting that urinary NGF levels can be a useful biomarker for detecting the severity of the bladder condition in patients with IC/BPS.