Seventeen observational studies (n=4,762 patients) and 20 RCTs (n=4,290 patients) were included in the review. The mean Jadad score for the RCTs was 3.5 (range 1 to 5). Duration of follow-up was one to 10 years in the observational studies and one to three years in the RCTs.
For observational studies (17 studies), the mean remission rate with disease-modifying antirheumatic drug (DMARD) monotherapy or combination therapy was 17% (eight studies) using ACR (American College of Rheumatology) criteria and remission rate of 33% (nine studies) using DAS (Disease Activity Score) criteria.
For the four RCTs that compared DMARD monotherapy with placebo/other treatment/other DMARD monotherapies, the remission rate was 19% with DMARD monotherapy therapy (three RCTs) and 12% with placebo therapy (one RCT).
For the 13 RCTS that compared DMARD monotherapy with DMARD combination therapy, the mean remission rate with monotherapy was 16% and with combination therapy was 24% by ACR criteria (six RCTs). Combination therapy was associated with significantly higher ACR remission rates than monotherapy (OR 1.69, 95% CI 1.21 to 2.36; NNT 12, 95% CI 8 to 33; I2=0%; seven RCTs). Mean remission rate with monotherapy was 26% and with combination therapy was 42% by DAS criteria. Combination therapy was associated with significantly higher DAS remission rates than monotherapy (OR 2.01, 95% CI 1.46 to 2.78; NNT 6, 95% CI 5 to 8; I2=68.6%; seven RCTs).
For three RCTs that compared DMARD combination therapies, remission rates by any criteria were 43% of patients.
For four observational studies, radiological progression ranged from 19 to 54% in patients with remission.
For two RCTs, less radiological progression was found with DMARD combination therapy when compared with DMARD monotherapy in patients with remission.