Twenty-four studies were included but data were reported only on the 11 studies that were entered into the meta-analysis (4,759 patients). Seven of the 11 studies were RCTs (four double blind, one single blind and two not blinded); two were rated high, two good and three fair. There were also four comparative cohort studies; one was rated fair and three were rated low quality. Efficacy outcomes were derived from RCTs in patients with RRMS. The analysis of adverse events included all studies and all patients. Drop-out ranged from 5.9% to 26%.
Relapse-free: No statistically significant differences were found between glatiramer acetate and placebo (moderate to high heterogeneity, Ι²=44.5%; four studies) or between glatiramer acetate and interferon (no heterogeneity, Ι² = 0%; two studies).
Mean number of relapses: There was a reduced mean number of relapses for patients who received glatiramer acetate compared with placebo (SMD -0.54, 95% CI -0.89 to -0.19; three studies; Ι²=67.5%) but with high statistical heterogeneity.
Clinical progression: There was a statistically significant benefit for glatiramer acetate compared with interferon (RR 0.82, 95% CI 0.68 to 0.98; two studies; Ι²=0%) but not when compared to placebo.
Change in EDSS scale: Change from baseline was statistically significantly higher for glatiramer acetate compared with placebo at 13 to 24 months (SMD -0.25, 95% CI -0.49 to -0.04; two studies; Ι² not reported) and at 24 months follow-up (SMD -0.39, 95% CI -0.66 to -0.11; one study).
Adverse events: Receiving glatiramer acetate was associated with a statistically significant increased risk of discontinuation due to adverse events compared with placebo (RR 3.13, 95% CI 1.38 to 7.12; four studies; Ι²=0%) but not compared with interferon (four studies; Ι²=0%). Glatiramer acetate was associated with a statistically significant increased risk of any injection site reaction compared with placebo (RR 1.88, 95% CI 1.24 to 2.86; two studies; Ι²=87.5%) but there was very high statistical heterogeneity. No statistically significant difference for injection site reaction was found compared with interferon (two studies; no statistical heterogeneity). For post-injection reaction, there was a greater risk in patients receiving glatiramer acetate compared with placebo (RR 3.39, 95% CI 2.34 to 4.90; four studies) with no statistical heterogeneity. There was also a statistically significant increased risk of post-injection reaction compared with interferon (RR 3.45, 95% CI 1.44 to 8.22; three studies; Ι²=67.5%) but with high statistical heterogeneity.
No evidence was found to indicate the presence of publication or small study biases. Further results at specific follow-up periods were reported in the paper.