Could urinary nerve growth factor be a biomarker for overactive bladder? A meta-analysis.

OBJECTIVE: The previously reported association between urinary nerve growth factor (NGF) and overactive bladder (OAB) was controversial. We performed this meta-analysis based on current available studies to sum up all evidence on this association.

METHODS: Studies were identified by searching PubMed, Embase, and Cochrane library from inception to September 2016. Pooled standardized mean difference (SMD) with their corresponding 95% confidence intervals (CIs) were calculated using a random-effects model.

RESULTS: A total of 17 published studies were included in this meta-analysis. Among the studies considered, patients with OAB had a significant higher baseline urinary NGF/Cr (NGF normalized to urine creatinine) level compared to those of controls (SMD = 0.74, 95%CI = 0.43-1.04, P < 0.00001). After treatment, the level of NGF/Cr decreased significantly in OAB group. However, there was no significant difference between patients with IC (interstitial cystitis)/PBS (painful bladder syndrome) and patients with overactive bladder (OAB) with regard to the urinary NGF/Cr level (SMD = 0.18, 95%CI = -0.06 to 0.41, P = 0.14). There was a statistically significant heterogeneity among included studies (P < 0.00001, I2  = 85%). No obvious evidence of significant publication bias was detected. In conclusion, this meta-analysis indicates that urine NGF/Cr may be a useful biomarker for OAB in the future. Because of lack of specificity, it seems that NGF/Cr cannot be used as a biomarker for OAB at present. Nevertheless, combined with other biological indicators may improve its specificity in diagnosis. More high quality studies that control the compounding factors strictly should be conducted in the future.