Optimal frequency of visits for patients with systemic lupus erythematosus to measure disease activity over time.

OBJECTIVE: adjusted mean Systemic Lupus Erythematosus Disease Activity Index (SLEDAI; AMS) measures lupus disease activity over time. Our aim was to determine optimal visit frequency for calculating AMS.

METHODS: patients followed monthly for 12 consecutive visits were included. AMS was calculated using all of the SLEDAI 2000 (AMS(GOLD) using all 12 visits), only quarterly visits (AMS(3), using visits 3 months apart), semiannual visits (AMS(6), using first, middle, and last visits only), and annual visits (AMS(12), using only the first and last visits). Comparisons of AMS(3), AMS(6), and AMS(12) with AMS(GOLD) are made using descriptive statistics.

RESULTS: seventy-eight patients were included (92% women, mean age at SLE diagnosis 30.1 yrs and at study start 46.2 yrs). The mean (SD) AMS(GOLD) for the entire year was 2.05 (1.66), for AMS(3) 1.99 (1.65), for AMS(6) 2.12 (1.87), and for AMS(12) 2.08 (1.83). Mean (SD) of the absolute differences with AMS(GOLD): for AMS(3) 0.29 (0.33), for AMS(6) 0.45 (0.59), and for AMS(12) 0.61 (0.58). Differences that were < 0.5 were considered minimal while those ≥ 1 were deemed important. Comparing AMS(GOLD) to AMS(3), 82% of the differences were minimal and 3% were important. When comparing to AMS(6), 68% were minimal and 10% were important, while comparing to AMS(12), 50% were minimal and 21% were important.

CONCLUSION: usual clinic visits occurring quarterly offer a good estimation of disease activity over a 1-year period and are preferred over semiannual and annual visits.