Search terms included a combination of MeSH terms and keywords: “diabetes mellitus,” “type 2 diabetes mellitus,” “DPP-4 inhibitor,” “Dipeptidyl peptidase 4 inhibitors,” “vildagliptin,” “sitagliptin,” “linagliptin,” “alogliptin,” “HbA1c,” “blood glucose levels,” and “adverse events. Here, DPP4 is linked to diabetes mellitus.