A-MUPS score to differentiate patients with somatic symptom disorder from those with medical disease for complaints of non-acute pain

Abstract

Purpose: To develop a clinical score to discriminate patients with somatic symptom disorder (SSD) from those with medical disease (MD) for complaints of non-acute pain.

Methods: We retrospectively examined the clinical records of consecutive patients with pain for a duration of ≥1 month in our department from April 2003 to March 2015. We divided the subjects according to the diagnoses of definite SSD (as diagnosed and tracked by psychiatrists in our hospital), probable SSD (without evaluation by psychiatrists in our hospital), matched MD (randomly matched two patients by age, sex, and pain location for each definite SSD patient), unmatched MD, other mental disease, or functional somatic syndrome (FSS). We investigated eight clinical factors for definite SSD and matched MD, and developed a diagnostic score to identify SSD. We subsequently validated the model with cases of probable SSD and unmatched MD.

Results: The number of patients with definite SSD, probable SSD, matched MD, unmatched MD, other mental disease, and FSS was 104 (3.5%), 214 (7.3%), 197 (6.7%), 742 (25%), 708 (24%), and 978 (33%), respectively. In a conditional logistic regression analysis, the following five factors were included as independent predictors of SSD: Analgesics ineffective, Mental disorder history, Unclear provocative/palliative factors, Persistence without cessation, and Stress feelings/episodes (A-MUPS). The area under the receiver operating characteristic curve (AUC) of the model was 0.900 (95% CI: 0.864-0.937, p<0.001), and the McFadden's pseudo-R-squared was 0.709. For internal validation, the AUC between probable SSD and unmatched MD was 0.930 (95% CI: 0.910-0.950, p<0.001). The prevalence and the likelihood ratio of SSD increased as the score increased.

Conclusion: The A-MUPS score was useful for discriminating patients with SSD from those with MD for complaints of non-acute pain, although external validation and refinement should be needed.

Keywords: functional somatic syndrome; hypochondriasis; medically unexplained; pain disorder; somatization; somatoform.

Figure 1

Flowchart and classification of the patients. Notes: *Including SSD if the primary diagnosis was another mental disorder. ^§Not combined with the diagnosis of SSD. Abbreviations: SSD, somatic symptom disorder; FSS, functional somatic syndrome; MD, medical disease.

Figure 2

Receiver operating characteristic curves according to the five scores in derivation and validation phases. Abbreviations: SSD, somatic symptom disorder; MD, medical disease; FSS, functional somatic syndrome.

Figure 3

Prevalence and likelihood ratio of SSD in validation phase (probable SSD versus unmatched MD). Abbreviations: A-MUPS, Analgesics ineffective, Mental disorder history, Unclear provocative/palliative factors, Persistence without cessation, and Stress feelings/episodes; SSD, somatic symptom disorder; MD, medical disease; NA, not applicable.

Figure 4

Prevalence and likelihood ratio of SSD in validation phase (all SSD versus all MD). Abbreviations: A-MUPS, Analgesics ineffective, Mental disorder history, Unclear provocative/palliative factors, Persistence without cessation, and Stress feelings/episodes; SSD, somatic symptom disorder; MD, medical disease; NA, not applicable.

Figure 5

Prevalence and likelihood ratio of SSD + FSS in validation phase (all SSD + FSS versus all MD). Abbreviations: A-MUPS, Analgesics ineffective, Mental disorder history, Unclear provocative/palliative factors, Persistence without cessation, and Stress feelings/episodes; SSD, somatic symptom disorder; FSS, functional somatic syndrome; MD, medical disease; NA, not applicable.

Figure 6

Prevalence and likelihood ratio of SSD in validation phase (all SSD versus all MD + FSS). Abbreviations: A-MUPS, Analgesics ineffective, Mental disorder history, Unclear provocative/palliative factors, Persistence without cessation, and Stress feelings/episodes; SSD, somatic symptom disorder; MD, medical disease; FSS, functional somatic syndrome.