Table 2.

Lloyd-Smith hierarchy of evidence

Level of evidence	Study design	Articles
1a	Meta-analysis of randomized controlled study
1b	Individual randomized controlled study	Baskurt et al. (2011) Struyf et al. (2013) Moezy et al. (2014) Turgut et al. (2017)
2a	Well designed, non randomized controlled study	Hotta et al. (2017)
2b	Well designed quasi experimental study	Bernardsson et al. (2011) Shankar et al. (2016)
3	Nonexperimental descriptive studies-comparative/case studies
4	Respectable opinion