Final answer:
Before administering etanercept, a nurse should primarily review the Liver function tests to monitor for potential hepatotoxicity.
Step-by-step explanation:
Before administering etanercept to a client with rheumatoid arthritis, a nurse should review the client's C) Liver function tests. Etanercept is a biologic medication that can affect liver enzymes, so it is important to ensure that the liver is functioning properly before initiating treatment. As etanercept works by inhibiting tumor necrosis factor (TNF), which plays an integral role in inflammatory and immune responses, monitoring liver enzymes is critical to identify any potential hepatotoxicity early on. Although serum creatinine, platelet count, and serum potassium are important values, they are not the primary concerns with etanercept therapy.