Qualitative research

In-depth interviews were performed with all LHWs who delivered BPHS and leaders who were responsible for the BPHS programme in the study PHC sectors. During recruitment, all LHWs who deliver BPHS and leaders who are responsible for the BPHS programme in the study PHC sectors were approached and provided with detailed explanations about the study and its objectives. Those who expressed interest in volunteering to participate in the in-depth interview were asked to read the informed consent form and then were asked to sign the informed consent form as a confirmation of their voluntary participation in the study. In-depth interviews were facilitated by semi-structured topic guides. The topic guide for leaders (see Additional file 1) mainly elicited information about their perspectives on the human resource situation for BPHS (i.e., the number of LHWs delivering BPHS in their own PHC sector, the quality of those LHWs and the stability of LHWs), perspectives on the current LHW training programme, problems with the current training programme, and the need for further training. The topic guides for LHWs (see Additional file 2) included their self-assessment of their competency to deliver BPHS, their participation in training, their perspective on the current training, and the need for further training.

All interviews were conducted in the local language in meeting rooms of PHC sectors or LHWs’ offices. The senior researchers (SLiang, SLiu, LL, YL) conducted the interviews. Each interview lasted approximately 40–60 min. All the interviews were audio-recorded with the consent of the participants.