Table 1

Inclusion criteria and justification

Types of participants
Exclusion of articles related to nursing, midwifery and allied health professionalsNursing, midwifery and allied health professions were excluded due to divergent issues related to gender and equitable participation.
North American, Western European, Australasian and available in the English languageOur geographical focus was chosen due to (1) established clinical academic career pathways in these regions and (2) the heavy influence of societal norms on attitudes to equitable participation which are relatively similar across these regions.54
Relevance to phenomena of interest (clinical academic career pipeline) within the context of diversity
Identifies factors that impact on equitable participation in the career pipeline (attractiveness, retention, success) Our aim was to synthesise the range of factors impacting on equitable participation. We therefore excluded research that
  •  measured markers of equitable participation (eg, publication or promotion rates).

  •  evaluated interventions to address equitable participation (eg, mentoring schemes).

  •  assessed the impacts of attrition (eg, on research quality).

 UNLESS they also empirically explored underlying reasons for unequal participation.
Conducted between 2005 and April 2019In 2005 Modernising Medical Careers was introduced in the UK, and current recommendations for clinical academic training were established.55
Types of publications
Exclusion of theoretical perspectives, commentaries, letters, opinion piecesOur aim was to identify robust conceptual categories and to explore their explanatory value. Our interest was in the concepts that had been identified by researchers, rather than the original raw data, ie second-order data.56 We therefore included empirical qualitative research, reviews grounded in robust empirical data, mixed methods studies with substantial qualitative elements and quantitative papers that tested a broad range of factors across demographics. Theoretical perspectives, commentaries and opinion pieces were excluded.
Subject to peer review and published in a reputable (non-predatory) journalPublication in a reputable journal following peer review was used as an initial surrogate for quality. Unpublished PhD theses, ongoing unpublished studies on trial registers, letters, conference abstracts, grey literature and suspected predatory journals57 were excluded.
Available in the English LanguageThe language criterion was partly pragmatic, and also to avoid the risk of misinterpreting constructs through translation.