Final answer:
The priority finding to report for a client with AIDS and on zidovudine is a decreased absolute neutrophil count (ANC), as it indicates potential bone marrow suppression and increased infection risk.
Step-by-step explanation:
The priority for the nurse to report to the provider in a client who has AIDS and is taking zidovudine is a decreased absolute neutrophil count (ANC). While a headache, which may also be a side effect of zidovudine, could be of concern, the ANC is more clinically significant given the potential for life-threatening complications. Neutrophils are a type of white blood cell essential for fighting infection.
A decrease in ANC, known as neutropenia, can indicate bone marrow suppression, a severe adverse effect of zidovudine, and increases the risk of opportunistic infections, which are particularly dangerous for patients with AIDS. As the patient's immune system is already compromised, with a typical diagnosis point for AIDS occurring when CD4 T-cell count drops below 200 cells/µL, maintaining adequate ANC levels is critical to protect against further infections and assessing the patient's safety for continued usage of the medication.