Which laboratory test should the nurse monitor before and during a client's treatment with valganciclovir?

A. Complete blood count: Valganciclovir can cause bone marrow suppression, leading to leukopenia, neutropenia, anemia, and thrombocytopenia. Monitoring CBC before and during therapy allows early detection of hematologic toxicity and guides dose adjustments or treatment interruptions to prevent severe cytopenias. B. Coagulation profile: Valganciclovir does not directly affect clotting factors or platelet function. Routine coagulation studies are not indicated unless the client has another condition affecting hemostasis. C. Thyroid panel: Valganciclovir has no significant effect on thyroid hormone synthesis or regulation. Assessing TSH, T3, or T4 is not necessary for standard therapy. D. Basic metabolic panel: Although renal function is important for dosing valganciclovir, the primary laboratory concern related to drug toxicity is hematologic, not metabolic. Monitoring electrolytes and kidney function may be indicated, but CBC remains the priority for safety.