TGM2 and type 1 diabetes mellitus: Notably, whereas anti-tTG antibodies have a >90% positive predictive value for CD, this is not the case for the aforementioned T1DM-related autoantibodies: indeed, the positive predictive value for T1DM of a single autoantibody is usually only around 10–25% and can increase up to 75% in case of positivity of three or more autoantibodies [86,87,88].