Embodiments disclosed herein provide reagents and methods for high-throughput screening of nucleic acid sequence variations in nucleic acid containing specimens. Nucleic acid specimens to be screened are loaded into separate discrete volumes. Optically encoded particles are used to deliver primers to amplify one or more sequences comprising the nucleic acid sequence variation. The optically encoded particles may be delivered to the discrete volumes randomly resulting in a random combination of optically encoded particles in each well, or a unique combination of optically encoded particles may be specifically assigned to each discrete volume. The observable combination of optically encoded particles may then be used to identify each discrete volume.