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. 2021 Sep 17;11(9):e049907. doi: 10.1136/bmjopen-2021-049907

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© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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Variation between practices in applying methods of registration. The figure was created by the author and permission for reuse is granted to BMJ Open. Method A: Patients with recorded FM, IBS, and/or CFS based on ICPC-codes. Method B: Patients with at least six ICPC codes that correspond to the Robbins list in any 6-month period. Method C: Patients with reported PSS-related terminology. Method D: Patients with ≥20 points on the somatisation subscale of the 4DSQ. 4DSQ, Four-Dimensional Symptom Questionnaire; CFS, chronic fatigue syndrome; FM, fibromyalgia; IBS, irritable bowel syndrome; ICPC, International Classification of Primary Care; PSS, persistent somatic symptoms.