title: Patient's global assessment of disease activity and patient's assessment of general health for rheumatoid arthritis activity assessment: are they equivalent?
abstract: OBJECTIVE
  To assess (A) determinants of patient's global assessment of disease activity (PTGL) and patient's assessment of general health (GH) scores of rheumatoid arthritis (RA) patients; (B) whether they are equivalent as individual variables; and (C) whether they may be used interchangeably in calculating common RA activity assessment composite indices.
  
  
  METHODS
  Data of 7023 patients from 30 countries in the Quantitative Standard Monitoring of Patients with RA (QUEST-RA) was analysed. PTGL and GH determinants were assessed by mixed-effects analyses of covariance models. PTGL and GH equivalence was determined by Bland-Altman 95% limits of agreement (BALOA) and Lin's coefficient of concordance (LCC). Concordance between PTGL and GH based Disease Activity Score 28 (DAS28), Clinical Disease Activity Index (CDAI) and Routine Assessment of Patient Index Data 3 (RAPID3) indices were calculated using LCC, and the level of agreement in classifying RA activity in four states (remission, low, moderate, high) using κ statistics.
  
  
  RESULTS
  Significant differences in relative and absolute contribution of RA and non-RA related variables in PTGL and GH ratings were noted. LCC of 0.64 and BALOA of -4.41 to 4.54 showed that PTGL and GH are not equivalent. There was excellent concordance (LCC 0.95-0.99) for PTGL and GH based DAS28, CDAI and RAPID3 indices, and >80% absolute agreement (κ statistics 0.75-0.84) in RA activity state classification for all three indices.
  
  
  CONCLUSIONS
  PTGL and GH ratings differ in their determinants. Although they are individually not equivalent, they may be used interchangeably for calculating composite indices for RA activity assessment.
authors.affiliation: Division of Rheumatology, University of Arkansas for Medical Sciences, 4301 West Markham Street, # 509, Little Rock, AR 72205, USA. nakhan@uams.edu
authors.forename: Nasim Ahmed
authors.initials: NA
authors.lastname: Khan
authors.forename: Horace Jack
authors.initials: HJ
authors.lastname: Spencer
authors.forename: Essam Ahmed
authors.initials: EA
authors.lastname: Abda
authors.forename: Rieke
authors.initials: R
authors.lastname: Alten
authors.forename: Christof
authors.initials: C
authors.lastname: Pohl
authors.forename: Codrina
authors.initials: C
authors.lastname: Ancuta
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Cazzato
authors.forename: Pál
authors.initials: P
authors.lastname: Géher
authors.forename: Laure
authors.initials: L
authors.lastname: Gossec
authors.forename: Dan
authors.initials: D
authors.lastname: Henrohn
authors.forename: Merete Lund
authors.initials: ML
authors.lastname: Hetland
authors.forename: Nevsun
authors.initials: N
authors.lastname: Inanc
authors.forename: Johannes Wg
authors.initials: JW
authors.lastname: Jacobs
authors.forename: Eduardo
authors.initials: E
authors.lastname: Kerzberg
authors.forename: Maria
authors.initials: M
authors.lastname: Majdan
authors.forename: Omondi
authors.initials: O
authors.lastname: Oyoo
authors.forename: Ruben A
authors.initials: RA
authors.lastname: Peredo-Wende
authors.forename: Zahraa Ibrahim
authors.initials: ZI
authors.lastname: Selim
authors.forename: Fotini Nikolaos
authors.initials: FN
authors.lastname: Skopouli
authors.forename: Alberto
authors.initials: A
authors.lastname: Sulli
authors.forename: Kim
authors.initials: K
authors.lastname: Hørslev-Petersen
authors.forename: Peter C
authors.initials: PC
authors.lastname: Taylor
authors.forename: Tuulikki
authors.initials: T
authors.lastname: Sokka
mesh_terms: D000328:Adult; D000368:Aged; D018771:Arthralgia / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000503:physiopathology* / Q000628:therapy; D016208:Databases, Factual; D005221:Fatigue / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D057566:Self Report; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires