NGF and interstitial cystitis: Urinary NGF levels may be elevated in numerous conditions of pathological bladder, for instance, overactive bladder, neurogenic bladder, interstitial cystitis/painful bladder syndrome, bladder outlet obstruction, etc. A meta-analysis in 2017 reported that urine NGF/Cr cannot be used as a biomarker for OAB at present, because of lack of specificity27.