Methodological decisions influence the identification of potential core outcomes in studies related to pre-eclampsia: an analysis informing the development of recommendations for future core outcome set developers

Objective To quantify the effect of different methodological decisions on the identification of potential core outcomes to inform the development of recommendations for future core coutcome set developers. Design Mixed methods study. Setting A core outcome set for pre-eclampsia was used as an exemplar. Sample A long list of potential core outcomes was developed by undertaking a systematic review of pre-eclampsia trials and performing a thematic analysis of in-depth patient interviews. Methods Specific methods used to generate long lists of potential core outcomes were evaluated. Results Different methodological decisions had a substantial impact on the identification of potential core outcomes. Extracting outcomes from published pre-eclampsia trials was an effective way of identifying 48 maternal, eight fetal, 25 neonatal outcomes, and eight patient-reported outcomes. Limiting the extraction of outcomes to primary outcomes or outcomes commonly reported in pre-eclampsia trials reduced the number and diversity of potential core outcomes identified. Thematic analysis of in-depth patient interviews ensured an additional five patient reported outcomes and six outcomes related to future child health were identified. Conclusions Future core outcome set developers should use quantitative and qualitative methods when developing a long list of potential core outcomes. Tweetable abstract @OfficialNIHR research published in @BJOGtweets informs new recommendations for future @coreoutcomes developers.