Systematic review sample we derived 26 articles with a focus on the structure of networks of health professionals, which met all the inclusion criteria and quality assessment criteria, and which were peer reviewed, empirical articles deploying recognised, clearly described research methods. Summary descriptive data from these studies were abstracted by one author (FCC) using a standard form to compile a tabular presentation of the study participants and setting, objec- tive, design and method, and ﬁndings. All authors reviewed this documentation for accuracy and complete- ness. Full information was available within the articles reviewed without the need to contact study authors. RESULTS Overview of studies The online appendix (table A) presents an overview of the 26 studies, including details of the study objective, participants, study dates, study context and ﬁndings. The online appendix (table B) also presents the research design and methodology of the studies, including a quality rating for each study, the data collection methods, sample size and response rate, and the type and level of analysis. Table 1 summarises the key study characteristics and table 2 presents the overall key structural ﬁndings relating to health network quality and safety. More than half (14) of the studies were published between 2004 and 2009. Half were undertaken in the USA, with hospital settings (11) representing the largest proportion. Of the 24 studies directed at health profes- sionals, seven focused on multidisciplinary groups of clinicians, with others primarily studying single health professions (nine) or single health domain professionals (six). Four studies researched healthcare collaboratives or partnerships. With respect to quality and safety, the studies have relevance to ﬁve of the six quality improvement dimen- sions identiﬁed by the Institute of Medicine,53 as indicated in the online appendix (table A, column 2): safe,30 31 34 35 41e43 49 effective,26 28 33 38 45 47 patient- centred,54 efﬁcient,35 39 48 50e52 and equitable.32 Time- liness was not addressed. Other aspects addressed by review studies with relevance to quality included culture,55 interdisciplinary teamwork,29 36 service inte- gration44 46 47 and stability,33 34 47 and diffusion of new practices.27 37 40 Research design and analytical approach As detailed in the online appendix (tables A and B), two studies used ethnography, while the 24 quantitative studies included case studies, multi-case studies, and cross-sectional studies. Principal data collection methods included surveys (23 studies), interviews (4), ethno- graphic observation (2) and archival data collection (2). 242 Table 1 Characteristics of studies Characteristic Year 1995e1999 2000e2004 2005e2009 Country USA Australia Canada UK Germany Italy Sweden Taiwan Setting Hospital based Community health based Primary and secondary care health professionals Healthcare collaboratives Aged care Multi-disciplinary research institute Type of health professional Multidisciplinary Mental health professionals Health service managers or administrative staff Nurses Medical practitioners Varied health professionals Dementia care professionals Study design Multi-case study Case study Cross-sectional study Ethnographic case study Level of analysis Actors and team Actors and organisation (or network) Organisation (or network) Actors, organisation and external network Data collection Survey Ethnography Archival data Number of studies 7 5 14 13 4 3 2 1 1 1 1 11 7 4 2 1 1 7 5 4 3 2 2 1 11 8 5 2 3 14 8 1 23 2 2 % 27 19 54 50 15 12 7 4 4 4 4 42 27 15 8 4 4 29 21 17 13 8 8 4 42 31 19 8 12 54 31 4 88 8 8 Most (19) used SNA to analyse data, with one study adding survival analysis, three studies using multiple regression, and two using other social science analyses. While 11 of the SNA studies had high response rates in the 90e100% range, the survey response rates varied from 100% or whole network samples39 47 to a low of 20%.38 The online appendix (table B, column 8) iden- tiﬁes the key aspects of network structure examined in each SNA study. BMJ Qual Saf 2012;21:239e249. doi:10.1136/bmjqs-2011-000187