Table 4.

Risk of bias table for intervention studies (observational: non-randomized clinical trials, cohort and case–control studies)

Study reference (first author, year of publication)	Bias due to a nonrepresentative or ill-defined sample of patients?	Bias due to insufficiently long, or incomplete follow-up, or differences in follow-up between treatment groups?	Bias due to ill-defined or inadequately measured outcome?	Bias due to inadequate adjustment for all important prognostic factors?
[21]	Unclear	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely
[15]	Unlikely Possible selection bias in dedicated team group, however they used a single-surgeon database	Unlikely However, large different in number of observed patients between groups	Unlikely	Unlikely (a multiregression model was provided for operating time, not for other outcome variables, however, as there were few cases adjustments would not be relevant) No adjustment for other factors that relate to time efficiency e.g. OR staff turnover or hospital-driven quality control measures
[22]	Unclear (uncontrolled before–after study)	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely
[25]	Unclear (uncontrolled before–after study)	Unlikely	Unlikely	Likely
[23]	Unlikely (minimal contamination)	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely
[19]	Unclear (uncontrolled before–after study)	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely
[20]	Unlikely Possible selection bias in dedicated team group over time (4 years later), however they used the same surgeons	Unlikely	Unlikely	Likely
[12]	Unclear (uncontrolled before–after study)	Unlikely	Unlikely Likely for observed outcome measures (not blinded) Teamwork outcomes are unclear	Likely
[14]	Unlikely (cluster RCT)	Unlikely	Unlikely	Unlikely (cluster RCT)
[17]	Unlikely	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely
[16]	Unclear	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely
[13]	Likely	Unlikely	Unlikely	Unlikely (propensity matching)
[24]	Unlikely	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely
[18]	Unlikely	Unlikely	Unlikely Likely for observed outcome measures (not blinded)	Likely