For the comparison of SGLT-2 inhibitors versus placebo, published randomised controlled trials do not include general populations of people with type 2 diabetes mellitus who meet the eligibility criteria of national guidelines for these three second line treatments (see supplementary table 21).7 It is therefore challenging to compare the results of the PERMIT study with those of the published randomised controlled trials. This evidence concerns the gene SLC5A2 and type 2 diabetes mellitus.