Provided below are ELISA kits targeting protein S, a human protein encoded by PROS1. This protein is 676 amino acids long with a reported mass of 75.1 kDa. This is reported to be a secreted protein. There is a noted implication in Thrombophilia due to protein S deficiency, autosomal dominant. Other alias names for this protein include: vitamin K-dependent protein S, protein S (alpha), protein Sa, vitamin K-dependent plasma protein S, PS21, PS22, and PS23. ELISA kits are available that are reactive to human, mouse, rat, bovine, chicken, primate, guinea pig, and other mammalian variants of the target antigen.