Measuring Inflammatory Arthritis in Patients with Systemic Lupus Erythematosus using Clinical Disease Activity Index

Background: Inflammatory polyarthritis is seen in (similar to)80% of patients with systemic lupus erythematosus (SLE); yet, there is no validated "instrument" for its assessment. The commonly used measures of disease activity, namely SLE Disease Activity Index 2000 (SLEDAI2K) and British Isles Lupus Assessment Group are complex and impractical for routine use in busy outpatient clinics. This "proof of concept" study's primary aim was to test clinical disease activity index (CDAI) as a possible instrument for measuring the joint disease in SLE that may have a face value and sensitivity to change. The secondary aim was to determine the efficacy of low-dose methotrexate in the SLE joint disease. Materials and Methods: This open-label study included the Systemic Lupus International Collaborating Clinics criteria classifiable thirty patients with SLE with inflammatory polyarthritis as the main manifestation. SLE disease activity and the joint disease activity were assessed using SLEDAI2K and CDAI, respectively, at the baseline and in the follow-up. The CDAI and the SLEDAI2K scores were compared between the first and the last visit, as well as compared with each other, using a nonparametric test (Wilcoxon signed-rank test). Results: CDAI scores improved significantly on treatment from a mean of 19.30 to 1.58 and in SLEDAI2K from 7.83 to 0.6, respectively; the pre- and the postintervention scores were statistically highly significant (P < 0.001) for both the CDAI and the SLEDAI2K. The degree of improvement as shown by SLEDAI2K change in scores and CDAI was statistically insignificant (P > 0.05), indicating similarity in their sensitivity to change. A significant number of patients achieved low disease activity status or remission in their joint disease. Conclusion: CDAI appears to be sensitive to change with treatment. Therefore, it could be used as a tool for assessing inflammatory arthritis in SLE.