The Protein Digestibility-Corrected Amino Acid Score (PDCAAS) compares the amino acid pattern of a protein to the amino acid needs of a 2-5 year old, with a correction factor based on protein digestibility. If the PDCAAS is greater than or equal to 1.00, the protein is a good source of essential amino acids. PDCAAS is the official measure used by the World Health Organization, among others.