title: Typology of patients with fibromyalgia: cluster analysis of duloxetine study patients.
abstract: BACKGROUND
  To identify distinct groups of patients with fibromyalgia (FM) with respect to multiple outcome measures.
  
  
  METHODS
  Data from 631 duloxetine-treated women in 4 randomized, placebo-controlled trials were included in a cluster analysis based on outcomes after up to 12 weeks of treatment. Corresponding classification rules were constructed using a classification tree method. Probabilities for transitioning from baseline to Week 12 category were estimated for placebo and duloxetine patients (Ntotal = 1188) using logistic regression.
  
  
  RESULTS
  Five clusters were identified, from "worst" (high pain levels and severe mental/physical impairment) to "best" (low pain levels and nearly normal mental/physical function). For patients with moderate overall severity, mental and physical symptoms were less correlated, resulting in 2 distinct clusters based on these 2 symptom domains. Three key variables with threshold values were identified for classification of patients: Brief Pain Inventory (BPI) pain interference overall scores of <3.29 and <7.14, respectively, a Fibromyalgia Impact Questionnaire (FIQ) interference with work score of <2, and an FIQ depression score of ≥5. Patient characteristics and frequencies per baseline category were similar between treatments; >80% of patients were in the 3 worst categories. Duloxetine patients were significantly more likely to improve after 12 weeks than placebo patients. A sustained effect was seen with continued duloxetine treatment.
  
  
  CONCLUSIONS
  FM patients are heterogeneous and can be classified into distinct subgroups by simple descriptive rules derived from only 3 variables, which may guide individual patient management. Duloxetine showed higher improvement rates than placebo and had a sustained effect beyond 12 weeks.
authors.forename: Ilya A
authors.initials: IA
authors.lastname: Lipkovich
authors.forename: Ernest H
authors.initials: EH
authors.lastname: Choy
authors.forename: Peter
authors.initials: P
authors.lastname: Van Wambeke
authors.forename: Walter
authors.initials: W
authors.lastname: Deberdt
authors.affiliation: Eli Lilly and Company, 3650 Danforth Avenue, Toronto, Ontario M1N 2E8, Canada. sagmand@lilly.com.
authors.forename: Doron
authors.initials: D
authors.lastname: Sagman
mesh_terms: D000328:Adult; D000700:Analgesics / Q000627:therapeutic use*; D016000:Cluster Analysis; D004311:Double-Blind Method; D000068736:Duloxetine Hydrochloride; D005260:Female; D005356:Fibromyalgia / Q000175:diagnosis* / Q000188:drug therapy* / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D013876:Thiophenes / Q000627:therapeutic use*
chemical_list: D000700:Analgesics; D013876:Thiophenes; D000068736:Duloxetine Hydrochloride