Abstract: A system and method predicts a phenotypic trait for an individual. The system identifies a subset of SNP loci with predictive ability of the phenotypic trait. The system calculates a PRS for the individual based on the individual's genetic dataset at the identified subset of SNP loci. The system compares the PRS to a threshold PRS. The threshold PRS is determined by calculating, for each training individual of a plurality of training individuals including some reported to have and some reported to not have the phenotypic trait, a PRS, sweeping through a domain of PRS while calculating a true positive rate and a false positive rate, and then identifying an optimal threshold PRS as the threshold PRS. The system generates a prediction whether the individual has the phenotypic trait based on the comparison.