A nurse is caring for a client who has HIV. Which of the following laboratory values is the nurse's priority?

Choice A reason: A positive Western blot confirms HIV diagnosis but is not a priority once diagnosis is established. Choice B reason: A CD4 count below 200 cells/mm³ indicates severe immunosuppression and increased risk for opportunistic infections, making it the priority. Choice C reason: Platelet count is within normal range and not immediately concerning. Choice D reason: WBC count is normal and does not indicate acute risk.