Amino acid score, in combination with protein digestibility, is the method used to determine if a protein is complete. PDCAAS and DIAAS are the two major protein standards which determine the completeness of proteins by their unique composition of essential amino acids. Amino acid score, in combination with protein digestibility, is the method used to determine if a protein is complete. PDCAAS and DIAAS are the two major protein standards which determine the completeness of proteins by their unique composition of essential amino acids.