Simplified Disease Activity Index as an index of disease activity in patients with rheumatoid arthritis: a comparison with DAS28

IntroductionVarious factors are known to determine the disease activity in patients with rheumatoid arthritis (RA). The main objective of this study was to establish the validity of the new tool of measurement of disease activity, Simplified Disease Activity Index (SDAI), in patients with RA in Indian population.MethodsAll patients with RA fulfilling the ACR classification criteria attending the rheumatology clinic at Nizam's Institute of Medical Sciences, Hyderabad over a period of 3 months were included in the study. A detailed assessment of each patient including their demographic characteristics, duration of the disease, number of tender and swollen joint counts, Westergren's ESR and C-reactive protein (mg/dL), patient's and physician's global assessment by VAS (0–10) were recorded. DAS28 and SDAI were calculated for each patient. Statistical analysis was done.ResultsTwo hundred and sixteen patients were included in the study comprising 184 women and 32 men. Mean age of the patients was 42.94 ± 11.23 years and mean duration of disease was 4.10 ± 4.02 years. Mean DAS28 and SDAI were 5.19 ± 1.48 and 24.2 ± 16.06 respectively. ROC curve revealed that discriminative ability of SDAI was better than that of DAS28. The optimal cut-off points for treatment changes were 4.46 for DAS28 (sensitivity 88%, specificity 87.5%) and 12.6 for SDAI (sensitivity 92%, specificity 83%).ConclusionSDAI is a valid tool for measurement of disease activity in RA in Indian population and is as good as DAS28 in its ability to assess the patient's status.