Significant differences exist in outcome measures developed to assess patients with primary Sjögren's Syndrome (pSS). In this review, we have compared proposed indices.
Three activity - SSDAI (SS Disease Activity Index), SCAI (Sjögren's Systemic Clinical Activity Index) and ESSDAI (EULAR SS Disease Activity Index) - and two damage indices - SSDDI (SS Disease Damage Index) and SSDI (SS Damage Index) have been analysed. Assessment 'tools' for perspectives of outcome (PROFAD - Profile of Fatigue and Discomfort, SF-36 - Medical Outcomes Study Short-Form 36-item questionnaire and ESSPRI - EULAR Sjögren's Syndrome Patients Reported Index) were also considered.
SSDAI and ESSDAI are global scores. SCAI is a composite score. Validity is a limitation for SSDAI and SCAI. ESSDAI is complemented by ESSPRI for the assessment of subjective features. It is more accurate in detecting changes in activity. Damage indices differ with respect to observation period and external validation but both have low content validity. Main limitations for all indices are: inclusion of patients with mainly mild stable disease and lack of information about the completion time of the forms.
All indices demonstrate a potentially useful benefit but further, larger studies are needed to assess reliability and sensitivity to change, to validate their use in clinical trials. Improvement in our knowledge of pathophysiology and clinical evolution of pSS is important to address unresolved issues: whether to include prognostic factors for an adverse outcome, an agreed definition of flare and most notably the distinction between activity and damage.