Sir,We read with great interest the recent study by Misra et al.evaluating different surgical interventions for the treatment of pain associated with endometriosis.1 We understand the importance of this research to inform our clinical practice and extend our gratitude to the researchers, the women who participated in the study, and the research funder.BJOG: An International Journal of Obstetrics and Gynaecology has been at the forefront of reducing research waste by implementing several important interventions including the requirement to prospectively register randomised trials, implementing the Consolidated Standards of Reporting Trials (CONSORT) statement, and mandating the reporting of core outcome sets.2Reflecting upon this recent study presents an opportunity to consider the impact of implementing such initiatives on selective outcome reporting. The authors prospectively registered their trial (ISRCTN50928834) and reported their pre-specified primary outcome as pelvic pain. This differs from the primary outcome reported in the final publication. A secondary outcome, dyspareunia, reported in the final publication, was not prospectively registered. The CONSORT statement commits researchers to report all prespecified primary and secondary outcomes. When new outcomes are added this should be made clear in the final publication and a comprehensive explanation provided. It would be useful for the authors to clarify the discrepancies between the prospective registry record and the published trial report.Core outcomes aim to address the challenges of poorly selected, collected, and reporting outcomes, including tackling outcome reporting bias.3 We are grateful to the authors for acknowledging the development of a core outcome set for endometriosis research within their study report. The core outcome set for endometriosis has recently been published and was developed using formal consensus methods involving 116 healthcare professionals, 32 researchers, and 206 women with endometriosis from 29 countries.4 The core outcomes include overall pain, improvement in most troublesome symptom, quality of life, adverse events, and patient satisfaction with treatment. It would be useful for the authors to clarify if the core outcomes had been collected as part of the trial and report available data.Over eighty speciality journals, including the Cochrane Gynaecology and Fertility Group, have committed to supporting the development, dissemination, and implementation of the core outcome set for endometriosis. The collaboration who have developed the core outcome set for endometriosis are now assisting with implementation and are systematically examining published endometriosis trials. Where inconsistencies between the trial registry record and the outcomes reported in the published trial report are identified or when the core outcome set has not been fully reported we are writing to the authors seeking clarification. Our progress can be followed at https://twitter.com/EndoOutcomes where we will be posting the prospective registry record, final publication, and response to this letter.