Methods of predicting the immunogenicity of a therapeutic protein in a subject are provided and the use of this method in selecting a protein for replacement therapy having the fewest immunogenic epitopes. The method is demonstrated by reference to ADAMTS13. Isolated allelic variants of ADAMTS13 that contribute to the variability in risk for both arterial and venous thrombotic disease development are provided. The allelic variants are identified as single nucleotide polymorphisms (ns-SNPs) in the ADAMTS13 gene, which result in haplotypes identified as H1 to H14. A method for improving outcomes of transfusions/transplant products is also provided by selection of haplotype matched therapeutics.
