title: Different wording of the Patient Global Visual Analogue Scale (PG-VAS) affects rheumatoid arthritis patients' scoring and the overall Disease Activity Score (DAS28): a cross-sectional study.
abstract: OBJECTIVE
  The Disease Activity Score in 28 joints (DAS28) is a key measure in clinical practice and clinical trials. There are at least five different versions of the 'Patient Global' Visual Analogue Scale (PG-VAS) being used in the DAS28. The developers suggested that the PG-VAS can be an assessment of global health or disease activity, but did not specify the wording of the question. There is no consensus on what the PG-VAS is intended to capture, and the different words and phrases have not been evaluated. The aim of this study was to test if phrasing affects PG-VAS scores and hence yields different results for the DAS28.
  
  
  METHODS
  Fifty patients with rheumatoid arthritis taking biologic agents in a rheumatology outpatient department completed a self-administered questionnaire containing five versions of the 100 mm PG-VAS.
  
  
  RESULTS
  All PG-VAS versions correlated strongly with each other (rho = 0.67-0.87, p < 0.0001). However, individual scores for each PG-VAS, when compared with the comparator on a Bland-Altman chart had wide limits of agreement--the largest being -42 mm to +45 mm. The five overall DAS28 scores were calculated for each patient using the five different PG-VAS. The largest difference in DAS28 scores was 0.63.
  
  
  CONCLUSIONS
  Different phrasing of the PG-VAS gives different DAS28 results. As the DAS28 is a key outcome measure, such differences have the potential to influence clinical decisions relating to eligibility for biologic agents and evaluation of new therapies. We urgently need to decide on the concept to be measured and the phrasing required to capture this. The PG-VAS phrasing should then be standardized and validated.
authors: Rheumatology Department, Bristol Royal Infirmary, Bristol, UK.
authors: Tracy
authors: T
authors: French
authors: Sarah
authors: S
authors: Hewlett
authors: John
authors: J
authors: Kirwan
authors: Tessa
authors: T
authors: Sanderson
mesh_terms: D000328:Adult; D000368:Aged; D018771:Arthralgia / Q000175:diagnosis* / Q000523:psychology / Q000628:therapy; D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000523:psychology / Q000628:therapy; D003430:Cross-Sectional Studies; D004644:Emotions; D005260:Female; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D010147:Pain Measurement / Q000379:methods* / Q000523:psychology*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires
keywords: DAS28; Rheumatoid arthritis; outcomes research; patient perspective