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Research paper
Somatic symptom count scores do not identify patients with symptoms unexplained by disease: a prospective cohort study of neurology outpatients
  1. Alan J Carson1,2,
  2. Jon Stone2,
  3. Christian Holm Hansen3,
  4. Rod Duncan4,
  5. Jonathon Cavanagh5,
  6. Keith Matthews6,
  7. G Murray7,
  8. Michael Sharpe8
  1. 1Department of Psychiatry, University of Edinburgh, Edinburgh, UK
  2. 2Department of Clinical Neurosciences, University of Edinburgh, Edinburgh, UK
  3. 3Department of Medical Statistics, University of Edinburgh, Edinburgh, UK
  4. 4Department of Neurology, University of Otago, Christchurch, New Zealand
  5. 5Department of IHW, University of Glasgow, Glasgow, UK
  6. 6Division of Neuroscience, University of Dundee, Dundee, UK
  7. 7Department of Public Health Sciences, University of Edinburgh Medical School, Edinburgh, UK
  8. 8Department of Psychiatry, University of Oxford, Oxford, UK
  1. Correspondence to Dr Alan Carson, Royal Edinburgh Hospital, Tipperlin Road, Edinburgh EH10 5HF, UK; a.carson{at}


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.


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