There are 11 and 17 allelic differences at p<0.05 in the PD-Prodrome, and PD-SWEDD comparisons respectively, but only the protective HLA-DQA1*03:03:01 in the PD-Prodrome comparison is significant (Pc=0.066) after the Bonferroni correction. Here, HLA-DQA1 is linked to Parkinson disease.