Filters are pre-written search strategies designed to retrieve a particular type of record. The Cochrane Highly Sensitive Search Strategy (HSSS) for identifying randomized trials in MEDLINE has been developed and tested and can be added to your search strategy to retrieve RCTs & quasi RCTS.
See Section 4.4.7 Search filters of the Cochrane Handbook for full details of search filters and Technical Supplement to Chapter 4: Searching for and selecting studies 3.6 Search filters (page 58-63)
An Embase study design filter (see Identifying Embase RCTs and CCTs for inclusion in CENTRAL) has been created by the team involved in the Embase Project.
An Embase animal filter was developed by Anne Eisinga of the UK Cochrane Centre in 2013.
A search filter to identify randomized controlled trials in CINAHL has been developed by Glanville et al. See: Glanville J, Dooley G, Wisniewski S, Foxlee R, Noel‐Storr A. Development of a search filter to identify reports of controlled clinical trials within CINAHL Plus. Health Information & Libraries Journal. 2019 Mar;36(1):73-90.
See also the poster from HTAi 2019