Validity of Simplified Ankylosing Spondylitis Disease Activity Scores (SASDAS) in Indian Ankylosing Spondylitis Patients.

Introduction: Ankylosing Spondylitis Disease Activity Score (ASDAS) is a complex score for monitoring disease activity in Ankylosing Spondylitis (AS).

Aim: To develop a simplified version of the ASDAS.

Materials and Methods: Consenting 254 AS patients (modified New York and/or Assessment in Ankylosing Spondylitis 2009 criteria) were recruited. Sociodemographic data and disease characteristics such as Bath AS Disease Activity Index (BASDAI), Bath AS Functional Index (BASFI), and AS Quality of Life (ASQoL), Erythrocyte Sedimentation Rate (ESR), and C-Reactive Protein (CRP) were collected. Simplified ASDAS (SASDAS) was calculated as the simple sum of patient global assessment, back pain (BASDAI question no.2), peripheral pain and swelling (BASDAI question no.3), morning stiffness (BASDAI question no.6), and either ESR in mm/hour (for SASDAS-ESR) or CRP in mg/L (for SASDAS-CRP); this sum was divided by 10 to obtain the final score.

Results: Most patients (224/254; 88.19%) were males with the median age of 30 years. SASDAS-ESR and SASDAS-CRP showed good correlation with ASDAS-ESR and ASDAS-CRP respectively (r2=0.78 and 0.58 respectively; p-value<0.0001). SASDAS-ESR showed good correlation with CRP (r=0.50) and is fairly correlated with backpain (r=0.19), morning stiffness (r=0.21) and peripheral pain (r=0.21); SASDAS-CRP showed good correlation with BASFI (r=0.32), and ESR (r=0.55) (all p-value<0.0001). Using established ASDAS cut-off values, corresponding cut-off points between 'inactive', 'moderate', 'high', and 'very high' disease activities (with optimum sensitivity and specificity) were 1.83, 2.45 and 4.45 for SASDAS-ESR, and 0.79, 1.50, and 3.26 for SASDAS-CRP. Both the SASDAS scores showed good correlation with BASDAI.

Conclusion: SASDAS-ESR and SASDAS-CRP are reliable, easy-to-calculate scores for disease activity assessment in Asian Indian AS patients; which can be used in daily clinical practice.