title: Qualitative "trial-sibling" studies and "unrelated" qualitative studies contributed to complex intervention reviews.
abstract: To compare the contribution of "trial-sibling" and "unrelated" qualitative studies in complex intervention reviews.
  
  
  
  Researchers are using qualitative "trial-sibling" studies undertaken alongside trials to provide explanations to understand complex interventions. In the absence of qualitative "trial-sibling" studies, it is not known if qualitative studies "unrelated" to trials are helpful. Trials, "trial-sibling," and "unrelated" qualitative studies looking at three health system interventions were identified. We looked for similarities and differences between the two types of qualitative studies, such as participants, intervention delivery, context, study quality and reporting, and contribution to understanding trial results.
  
  
  
  Reporting was generally poor in both qualitative study types. We detected no substantial differences in participant characteristics. Interventions in qualitative "trial-sibling" studies were delivered using standardized protocols, whereas interventions in "unrelated" qualitative studies were delivered in routine care. Qualitative "trial-sibling" studies alone provided insufficient data to develop meaningful transferrable explanations beyond the trial context, and their limited focus on immediate implementation did not address all phenomena of interest. Together, "trial-sibling" and "unrelated" qualitative studies provided larger, richer data sets across contexts to better understand the phenomena of interest.
  
  
  
  Findings support inclusion of "trial-sibling" and "unrelated" qualitative studies to explore complexity in complex intervention reviews.
authors.affiliation: School of Social Sciences, Bangor University, Bangor, LL57 2EF, UK. Electronic address: j.noyes@bangor.ac.uk.
authors.forename: Jane
authors.initials: J
authors.lastname: Noyes
authors.affiliation: North Wales Centre for Primary Care Research, Bangor University, Gwenfro Units 4-8, Wrexham Technology Park, Wrexham LL13 7YP, UK.
authors.forename: Margaret
authors.initials: M
authors.lastname: Hendry
authors.affiliation: Global Health Unit, Norwegian Knowledge Centre, Norwegian Institute of Public Health, PO Box 4404, Nydalen, N-0403 Oslo, Norway; Health Systems Research Unit, South African Medical Research Council, Francie van Zijl Drive, Parowvallei, Cape, PO Box 190707505 Tygerberg, South Africa.
authors.forename: Simon
authors.initials: S
authors.lastname: Lewin
authors.affiliation: Global Health Unit, Norwegian Knowledge Centre, Norwegian Institute of Public Health, PO Box 4404, Nydalen, N-0403 Oslo, Norway.
authors.forename: Claire
authors.initials: C
authors.lastname: Glenton
authors.affiliation: The Cochrane Editorial Unit, Cochrane Central Executive, St Albans House, 57-59 Haymarket, London SW1Y 4QX, UK.
authors.forename: Jackie
authors.initials: J
authors.lastname: Chandler
authors.affiliation: Department of Health Management and Economics, Tehran University of Medical Science, Tehran, Iran.
authors.forename: Arash
authors.initials: A
authors.lastname: Rashidian
mesh_terms: D016021:Epidemiologic Studies; D006801:Humans; D036301:Qualitative Research; D012196:Review Literature as Topic
keywords: Complex intervention; Implementation; Methodological exemplar; Mixed-methods; Qualitative; Systematic review; Trial