NGF and Bartsocas-Papas syndrome 1: In the selected studies, BPS or IC patients seemed to have a high urinary NGF level when compared with controlled participants (WMD = 36.39, 95 % CI 13.27–59.51; z = 3.08, P = 0.002), Fig. 2 showed the difference of urinary NGF level in BPS/IC group and controlled group.