Table 2.

Stages of receipt and integration of feedback during the development of RoB-SPEO and main innovations introduced.

Stage	Feedback receipt and integration	Main innovations introduced
1	Three rounds of feedback on RoB-SPEO version (v.) 1 received from seven WHO and ILO experts and 130 individual experts on systematic review methods, occupational health and safety and/or exposure science and integrated in RoB-SPEO v.2	- Adopted and/or revised tool components from existing tools, including instructions, domains, guiding questions, considerations, ratings and rating criteria - Introduced concepts, terms and examples from occupational health and safety
2	Feedback on RoB-SPEO v.2 received from five external systematic review methodologists, 20 peer reviewers and two journal editors received, integrated in RoB-SPEO v.3, and this tool version published in systematic review protocols (e.g. Mandrioli et al., 2018) as prototype	- Further refined tool components, especially rating criteria - For each domain, added a description of the bias covered
3	Three rounds of feedback on RoB-SPEO v.3 received from eight WHO and ILO experts and 30 individual experts in systematic review methods, occupational health, occupational safety and/or exposure science and integrated in RoB-SPEO v.4	- Revised instructions - Substantially revised guiding questions - To improve comprehension and specificity, added several examples from exposure science - Further refined rating criteria - For each domain, added essential definitions of key terms and concepts
4	One round of feedback on RoB-SPEO v.4 received from pilot testers and integrated in RoB-SPEO v.5	- Introduced additional domain on bias due to differences in numerator and denominator - Introduced standard tables for reporting assessments by domain - Introduced new rating category (“No information”)
5	Feedback on RoB-SPEO v.5 received from two external systematic review methodologists, four peer reviewers and a journal editor and integrated in RoB-SPEO v.6 presented in this article	- Re-formatted tool for clarity, introducing subheadings to differentiate components - In the tables for reporting assessments by domain, added reporting of data extracted from study records to support assessments and ratings