RsIDs

rsIDs are unique identifiers assigned by the National Center for Biotechnology Information (NCBI) to specific genetic variants cataloged in the dbSNP database. The prefix rs stands for Reference SNP cluster ID, and an rsID serves as a stable reference to that variant across studies and resources. An rsID can refer to a single nucleotide polymorphism (SNP), as well as small insertions and deletions (indels) or other types of variation that are captured in dbSNP. The ID is used in literature and bioinformatics tools to report a variant unambiguously, independent of genomic coordinates or allelic representation.

Format and scope: An rsID takes the form of the letters “rs” followed by digits, such as rs1234567. Each rsID corresponds to a variant entry in dbSNP, which may include information about position on a reference genome, observed alleles, allele frequencies, and supporting evidence. Variants can be located anywhere in the genome and may have multiple alternative alleles; the rsID typically refers to the variant as defined in dbSNP, with associated metadata.

Assignment and maintenance: rsIDs are assigned after a variant is submitted to dbSNP and curated. The entry can be updated with new evidence or, in rare cases, merged with another entry or deprecated if found to be erroneous. Because genome builds evolve, the genomic coordinates linked to an rsID may change between reference assemblies, while the rsID itself generally remains a stable identifier.

Usage and caveats: rsIDs are widely used in genome-wide association studies and annotation pipelines to report variants consistently. Users should be mindful of build-specific coordinates and the possibility of updates or reannotations in dbSNP, which can affect mappings for older rsIDs.