Final answer:
A hematological finding that necessitates immediate discontinuation of Clozaril is agranulocytosis, a rare but serious side effect characterized by a severe decrease in the number of white blood cells.
Step-by-step explanation:
A hematological finding that necessitates immediate discontinuation of Clozaril (clozapine) is agranulocytosis. Agranulocytosis is a condition characterized by a severe decrease in the number of white blood cells called granulocytes, which are responsible for fighting infection. Clozaril can cause agranulocytosis as a rare but serious side effect, which can increase the risk of severe infections.