Li Z, Wang J, Han X, et al. - Since elevated serum cancer antigen 19-9 (CA19-9) levels were found in diabetes patients in most observational studies, researchers used the data of the Dongfeng-Tongji cohort (DFTJ cohort) study to determine if there was a causal connection between CA19-9 and diabetes mellitus. Between September 2008 and June 2010, 27,009 retired workers of the Dongfeng Motor Corporation were selected. During a mean 4.54-year follow-up period, a total of 1,004 incident diabetes mellitus patients were diagnosed. Findings suggested no causal association of serum CA19-9 with diabetes risk. CA19-9 could be a potential biomarker of incident diabetes mellitus risk.