*2.2. Data Collection*

All data regarding participants in the RTW program were obtained from BPJS Ketenagakerjaan. The authors sent the invitation to potential applicants through a widespread email. A total of 165 individuals in the RTW program who had been asked to participate in the study and met all prerequisites were enrolled at the outset. During the starting procedure, only 154 people agreed to be interviewed and completed our questionnaires. Moreover, we extended invitations to an additional 165 disabled patients who had had an occupational injury but were hesitant to take part in the RTW program. However, only 75 people agreed to participate in this study.

The data were collected by the first and third authors. The lead author conducted a three-hour training session on RTW, WAI, QoL, and instructions for data collection and ethical issues to 11 case managers of BPJS Ketenagakerjaan in 34 provinces throughout Indonesia before commencing the data collection. The case managers involved in this study were employees of BPJS Ketenagakerjaan and were not specifically added for the current study. The case managers acted as enumerators and collected data from patients participating in RTW programs at trauma centers and rehabilitation hospitals, and received training from the lead author on RTW, WAI, QoL, and data collection, and ethical issues. The data collection was carried out by 11 case managers in 34 provinces throughout Indonesia, who were assigned to hospitals based on their location. The data were collected through printed surveys to reduce nonresponse bias. The data collectors analyzed the recovered questionnaires to minimize missing responses and asked for responses in cases of missing items.

The questionnaire included topics on sociodemographic variables as well as disabilityrelated aspects. In addition, a questionnaire assessing the quality of life and work ability index was also included in the research. For the purpose of determining the quality of life (QOL) and the work ability index (WAI), respectively, the WHOQoL-BREF developed by the World Health Organization (WHO) and validated WAI questionnaires developed by the Finnish Institute of Occupational Health were used.
