Table 1.

Description of methods for PSS identification

	Method A	Method B	Method C	Method D
General PSS-related criteria	Irritable bowel syndrome, fibromyalgia and chronic fatigue syndrome	Frequent consultation for multiple PSS-related symptoms	Reported PSS-related terminology*	Somatic symptom subscale of the 4DSQ†
Criteria translated to EMR data	ICPC codes for chronic fatigue syndrome (A04.01), fibromyalgia (L18.01) and irritable bowel syndrome (D93)	Symptoms based on the ‘Robbins list’.‡ The symptoms have been linked to ICPC-codes	Terminology is based on a cross-search of the data with ICPC codes from methods A and B	The 4DSQ is a validated questionnaire available in EMRs of Dutch GPs
Duration/cut-off	At least 6 months, or at least two contact registrations.	At least six registrations with one or more relevant ICPC codes within a 6-month period	At least 6 months	A score of ≥20 on the somatic symptom subscale of the 4DSQ
Registration type	Based on episode and contact registration	Based on contact registration	Based on description in the episode registration	Laboratory test results

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*Examples of included terms: somatisation, psychosomatic, central sensitisation, atypical low back pain, stress related pain, interstitial cystitis, extreme fatigue, tension headache: good CT, functional.

†Four-dimensional symptom questionnaire.⁴²

‡Robbins list: Back pain, joint pain, extremity pain, headaches, fatigue/weakness, sleep disturbance, difficulty concentrating, loss of appetite, weight change, restlessness, thoughts slower, chest pain, shortness of breath, palpations, dizziness, lump in throat, numbness, nausea, loose bowels, gas/bloating, constipation, abdominal pain.⁵²

4DSQ, Four-Dimensional Symptom Questionnaire; EMR, electronic medical records; GP, general practitioner; ICPC, International Classification of Primary Care; PSS, persistent somatic symptoms.