Study question: What is the global consensus on the classification of endometriosis that considers the views of women with endometriosis?

Summary answer: We have produced an international consensus statement on the classification of endometriosis through systematic appraisal of evidence and a consensus process that included representatives of national and international, medical and non-medical societies, patient organizations, and companies with an interest in endometriosis.

What is known already: Classification systems of endometriosis, developed by several professional organizations, traditionally have been based on lesion appearance, pelvic adhesions, and anatomic location of disease. One system predicts fertility outcome and none predicts pelvic pain, response to medications, disease recurrence, risks for associated disorders, quality of life measures, and other endpoints important to women and health care providers for guiding appropriate therapeutic options and prognosis.

Study design, size, duration: A consensus meeting, in conjunction with pre- and post-meeting processes, was undertaken.

Participants/materials, setting, methods: A consensus meeting was held on 30 April 2014 in conjunction with the World Endometriosis Society's 12th World Congress on Endometriosis. Rigorous pre- and post-meeting processes, involving 55 representatives of 29 national and international, medical and non-medical organizations from a range of disciplines, led to this consensus statement.

Main results and the role of chance: A total of 28 consensus statements were made. Of all, 10 statements had unanimous consensus, however none of the statements was made without expression of a caveat about the strength of the statement or the statement itself. Two statements did not achieve majority consensus. The statements covered women's priorities, aspects of classification, impact of low resources, as well as all the major classification systems for endometriosis. Until better classification systems are developed, we propose a classification toolbox (that includes the revised American Society for Reproductive Medicine and, where appropriate, the Enzian and Endometriosis Fertility Index staging systems), that may be used by all surgeons in each case of surgery undertaken for women with endometriosis. We also propose wider use of the World Endometriosis Research Foundation Endometriosis Phenome and Biobanking Harmonisation Project surgical and clinical data collection tools for research to improve classification of endometriosis in the future, of particular relevance when surgery is not undertaken.

Limitations, reasons for caution: This consensus process differed from that of formal guideline development, although based on the same available evidence. A different group of international experts from those participating in this process may have yielded subtly different consensus statements.

Wider implications of the findings: This is the first time that a large, global, consortium-representing 29 major stake-holding organizations, from 19 countries - has convened to systematically evaluate the best available evidence on the classification of endometriosis and reach consensus. In addition to 21 international medical organizations and companies, representatives from eight national endometriosis organizations were involved, including lay support groups, thus generating and including input from women who suffer from endometriosis in an endeavour to keep uppermost the goal of optimizing quality of life for women with endometriosis.

Study funding/competing interests: The World Endometriosis Society convened and hosted the consensus meeting. Financial support for participants to attend the meeting was provided by the organizations that they represented. There was no other specific funding for this consensus process. Mauricio Abrao is an advisor to Bayer Pharma, and a consultant to AbbVie and AstraZeneca; G David Adamson is the Owner of Advanced Reproductive Care Inc and Ziva and a consultant to Bayer Pharma, Ferring, and AbbVie; Deborah Bush has received travel grants from Fisher & Paykel Healthcare and Bayer Pharmaceuticals; Linda Giudice is a consultant to AbbVie, Juniper Pharmaceutical, and NextGen Jane, holds research grant from the NIH, is site PI on a clinical trial sponsored by Bayer, and is a shareholder in Merck and Pfizer; Lone Hummelshoj is an unpaid consultant to AbbVie; Neil Johnson has received conference expenses from Bayer Pharma, Merck-Serono, and MSD, research funding from AbbVie, and is a consultant to Vifor Pharma and Guerbet; Jörg Keckstein has received a travel grant from AbbVie; Ludwig Kiesel is a consultant to Bayer Pharma, AbbVie, AstraZeneca, Gedeon Richter, and Shionogi, and holds a research grant from Bayer Pharma; Luk Rombauts is an advisor to MSD, Merck Serono, and Ferring, and a shareholder in Monash IVF. The following have declared that they have nothing to disclose: Kathy Sharpe Timms; Rulla Tamimi; Hugh Taylor.

Trial registration number: N/A.