title: Somatic symptom count scores do not identify patients with symptoms unexplained by disease: a prospective cohort study of neurology outpatients.
abstract: OBJECTIVE
  Somatic symptoms unexplained by disease are common in all medical settings. The process of identifying such patients requires a clinical assessment often supported by clinical tests. Such assessments are time-consuming and expensive. Consequently the observation that such patients tend to report a greater number of symptom has led to the use of self-rated somatic symptom counts as a simpler and cheaper diagnostic aid and proxy measure for epidemiological surveys. However, despite their increasing popularity there is little evidence to support their validity.
  
  
  METHODS
  We tested the score on a commonly used self-rated symptom questionnaire- the Patient Health Questionnaire (PHQ 15) (plus enhanced iterations including an additional 10 items on specific neurological symptoms and an additional 5 items on mental state) for diagnostic sensitivity and specificity against a medical assessment (with 18 months follow-up) in a prospective cohort study of 3781 newly attending patients at neurology clinics in Scotland, UK.
  
  
  RESULTS
  We found 1144/3781 new outpatients had symptoms that were unexplained by disease. The patients with symptoms unexplained by disease reported higher symptoms count scores (PHQ 15: 5.6 (95% CI 5.4 to 5.8) vs 4.2 (4.1 to 4.4) p<0.0001). However, the PHQ15 performed little better than chance in its ability to identify patients with symptoms unexplained by disease. The findings with the enhanced scales were similar.
  
  
  CONCLUSIONS
  Self-rated symptom count scores should not be used to identify patients with symptoms unexplained by disease.
authors.affiliation: Department of Psychiatry, University of Edinburgh, Edinburgh, UK Department of Clinical Neurosciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Carson
authors.affiliation: Department of Clinical Neurosciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Jon
authors.initials: J
authors.lastname: Stone
authors.affiliation: Department of Medical Statistics, University of Edinburgh, Edinburgh, UK.
authors.forename: Christian Holm
authors.initials: CH
authors.lastname: Hansen
authors.affiliation: Department of Neurology, University of Otago, Christchurch, New Zealand.
authors.forename: Rod
authors.initials: R
authors.lastname: Duncan
authors.affiliation: Department of IHW, University of Glasgow, Glasgow, UK.
authors.forename: Jonathon
authors.initials: J
authors.lastname: Cavanagh
authors.affiliation: Division of Neuroscience, University of Dundee, Dundee, UK.
authors.forename: Keith
authors.initials: K
authors.lastname: Matthews
authors.affiliation: Department of Public Health Sciences, University of Edinburgh Medical School, Edinburgh, UK.
authors.forename: G
authors.initials: G
authors.lastname: Murray
authors.affiliation: Department of Psychiatry, University of Oxford, Oxford, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Sharpe
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000553:Ambulatory Care; D015331:Cohort Studies; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000175:diagnosis* / Q000523:psychology; D009460:Neurologic Examination; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012017:Referral and Consultation; D057566:Self Report; D013001:Somatoform Disorders / Q000175:diagnosis* / Q000523:psychology; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: SOMATISATION DISORDER