An method for predicting the onset of type 1 diabetes (T1 D) ina subject, comprises the steps of: (a) measuring the concentration of at leastone amino acid, amino acid derivative or amino acid metabolite in a biologicalsample taken from the subject (b) determining the subjects HLA genotype(c) assigning the subjects genetic risk of developing T1 D on the basisof the subjects HLA genotype (d) combining the information obtainedin step (a) with the information in step (c) and (e) predicting the likelihoodof onset of T1 D based upon the combination of step (d). The diagnostic method canbe used to select target subjects for T1 D prophylactic treatment, and as partof a T1 D preventative treatment regime for neonates having a likelihood of developingchildhood T1 D.
