Fig. 1From: Retention in opioid agonist treatment: a rapid review and meta-analysis comparing observational studies and randomized controlled trialsFlowchart of studies. Comparison of retention in oral fixed-dose methadone versus buprenorphine Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram. Creative Commons Attribution License 4.0, adapted with permission [39]Back to article page