Recent systemic lupus erythematosus (SLE) randomised controlled trials (RCTs) were examined for potential design flaws and compared to rheumatoid arthritis (RA) RCT over the same time period to suggest modifications to SLE RCTs that could help improve the potential success rate of future SLE trials.
RA and SLE biologics RCTs published between 2005 and July 2013 were identified using PubMed. Inclusion criteria, study design, outcome measures, sample size calculations, patient baseline characteristics steroid use in the protocol and results were extracted and compared.
All trials required active disease for enrolment. Twenty-two RA RCTs and eight SLE RCTs were included. All RA RCTs used either a partial or continuous measure of improvement. SLE RCTs used SLEDAI, BILAG, SLAM, SRI and BICLA. RA trials were larger (543 vs. 376 participants). Concomitant corticosteroid use was stable in 100% of RA trials while all SLE RCTs allowed dose tapering. RA trials were mostly in methotrexate or DMARD inadequate responders whereas SLE trials allowed for the presence or absence immunosuppressives within all trials. Sample sizes in RA were determined on a change in disease activity or proportion meeting a disease state. Positive trials were found in 100% of RA RCTs and 25% of SLE RCTs.
The potential insensitivity of SLE disease activity indices to partial improvements may result in type II errors in SLE RCTs. Varying concomitant pharmacotherapy, especially corticosteroid use, in SLE may blunt observed treatment effects. Steroid tapering should be considered a trial outcome in isolation. More realistic sample size calculations are needed in SLE.