Efficacy of a smartphone application for helping individuals with type 2 diabetes mellitus manage their blood glucose: a protocol for factorial design trial oleh Hongxia Tang, Hua Qin, Mingjiao Zhang, Jihong Zhang, Huiwen Tan, Mengjie Chen, Laixi Kong, Maoting Guo, Fenghui Hu, Qin Wang, Xiaoxia Wang, Kun Zhang, Zhenzhen Xiong