A recently published systematic review identified diagnostic accuracy studies in the literature, which compared clinical criteria with C-peptide cut-offs.7 Age at diagnosis, time to insulin, and BMI are the clinical characteristics most frequently used to classify type 1 and type 2 diabetes, but few studies have addressed clearly which are most strongly associated with long-term C-peptide secretion.7 Where strength of association has been measured, time to insulin and age at diagnosis appear stronger than BMI. The gene discussed is INS; the disease is type 2 diabetes mellitus.