Table 4.

Study assessment using the Newcastle Ottawa Scale

Studies	Stars allocated following NOS assessment	No of stars (n)
Almagro 2015	*******	7
Berger 2004	******	6
Campo 2013	********	8
Enriquez 2011	*******	7
Konecny 2010	********	8
Nishiyama 2009	*******	7
Selvaraj 2005	******	6
Sung 2013	******	6
Zhang 2012	******	6

Abbreviations: NOS Newcastle Ottawa scale