Somatic symptom count scores do not identify patients with symptoms unexplained by disease [prospective cohort study...], 2015, Carson et al

Carson AJ, Stone J, Hansen CH, et al, Somatic symptom count scores do not identify patients with symptoms unexplained by disease: a prospective cohort study of neurology outpatients
Journal of Neurology, Neurosurgery & Psychiatry 2015;86:295-301
https://jnnp.bmj.com/lookup/pmidlookup?view=long&pmid=24935983

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.

 

I thought this was an interesting study 'nevertheless'.

Carson et al (2015):

"The total symptom count was greater for patients with symptoms unexplained by disease regardless of which combination of symptoms was included in the count (table 2).

"However, there was substantial overlap in the IQRs (figure 3). This suggests that while the total symptom count was greater in patients with unexplained symptoms, symptom count does not discriminate well between the groups. This poor discrimination was confirmed when we plotted ROC curves.

"These indicated sensitivities and specificities only just above chance, irrespective of which symptoms were counted or where ‘cut-offs’ were set (figure 4)."

Figure 2:



https://jnnp.bmj.com/content/jnnp/86/3/295/F2.large.jpg

Edit:
Note that this isn't a represntative patients sample:

"The clinics sampled took mainly general practice referrals with patients allocated by medical records staff according to availability of appointment. Tertiary clinics, where patients required a specific diagnosis to attend (such as acute neurovascular and multiple sclerosis clinics) were excluded as were ‘urgent case’ emergency clinics."

Patients
"All newly referred patients at the participating neurology outpatient clinics were potentially eligible for inclusion.

The exclusion criteria were: age less than 16 years, cognitive or physical impairment of a degree that precluded informed consent, inability to read English, or if the neurologist identified the patient as unsuitable for the study (eg, too distressed, terminally ill). New patients included patients with existing neurological diagnoses who had been referred again from primary care.

 

They renamed and redefined ME so the symptoms of ME now correspond to no known disease. They will never be medically explained if they continue - without giving a reason - to deny the medical explanation.