Studies were found that used this type of analysis for the diagnosis of breast cancer in saliva, obtaining an accuracy that ranged from 77% to 83.5% [28]; for the diagnosis and monitoring of diabetes mellitus in nail clippings, obtaining an accuracy of 92% [29]; for monitoring diabetes mellitus during treatment with insulin, in saliva, obtaining an accuracy of 98.8% [30]; and for the diagnosis of chronic kidney disease (CKD) in saliva, obtaining an accuracy of 82% [31]. This evidence concerns the gene INS and chronic kidney disease.