Objective. This study sets out to investigate the relationship between health status [EuroQol five-dimensions questionnaire (EQ-5D)] in primary SS and three of the European League Against Rheumatism (EULAR) SS outcome measures—the disease activity index (ESSDAI), the patient reported index (ESSPRI) and the sicca score. In particular, the goal was to establish whether there is a relationship between the EULAR outcome measures and quality of life.
Methods. Health status was evaluated using a standardized measure developed by the EuroQol Group—the EQ5D. This permits calculation of two measures of health status: time trade-off (TTO) values and the EQ-5D visual analogue scale (VAS) scores. We used Spearman’s rank correlation analysis to investigate the strength of association between health status and three EULAR measures of physician- and patient-reported disease activity in 639 patients from the UK primary SS registry (UKPSSR) cohort.
Results. This study demonstrates that the EULAR SS disease-specific outcome measures are significantly correlated with health outcome values (P <0.001). Higher scores on the ESSDAI, EULAR sicca score and ESSPRI are associated with poorer health states—i.e. lower TTO values and lower VAS scores. While all three are significantly correlated with TTO values and EQ-5D VAS scores, the effect is strongest for the ESSPRI.
Conclusion. This study provides further evidence supporting the use of ESSDAI, EULAR sicca score and ESSPRI measures in the clinic. We also discuss the need for disease-specific measures of health status and their comparison with standardized health outcome measures.