Nadir timing influences monitoring by guiding the timing of the CBC. Which option correctly identifies the test involved?

• A. Serum amylase.
• B. Lipid panel.
• C. Urinalysis.
• D. CBC.

Answer: (D)

Nadir timing refers to the period after chemotherapy when bone marrow suppression causes the lowest blood cell counts. To monitor this, the complete blood count is used because it directly shows the levels of white blood cells (especially the absolute neutrophil count), platelets, and hemoglobin. Tracking these values around the expected nadir lets clinicians detect neutropenia and thrombocytopenia, gauge infection risk, and decide whether to delay or modify treatment or provide supportive care. The other options don’t reflect marrow suppression or nadir timing: serum amylase, lipid panel, and urinalysis assess pancreatic function, lipid status, and kidney/infection markers, respectively, not bone marrow suppression from chemotherapy.