Provided below are ELISA kits targeting R-spondin 1, a human protein encoded by RSPO1. This protein is 263 amino acids long, with a mass of 29 kDa, and is a member of the R-spondin family. 3 isoforms have been identified. This is reported to be a nuclear and secreted protein. There is a noted implication in Keratoderma, palmoplantar, with squamous cell carcinoma of skin and sex reversal. Other alias names for this protein include: R-spondin homolog, roof plate-specific spondin-1, CRISTIN3, and RSPO. ELISA kits are available that are reactive to human, mouse, rat, chicken, primate, guinea pig, fish, and other mammalian variants of the target antigen.