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.
CONCLUSION: 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.