Nested case-control study investigating factors affecting initial adoption of HIV self-testing among men who have sex with men in Guangzhou, China: amidst comprehensive service coverage - Gu, Yuzhou; Yang, JiaLi; Luo, Yefei; Zhan, Lishan; Liu, Fanghua; Zeng, Wenting; Xu, Huifang; Lu, Yongheng; Cai, Yanshan; Han, Zhigang (Frontiers in Public Health, 2025)