Final answer:
The test that confirms herpes zoster is the Tzanck test, which involves examining cells from a blister caused by the virus. Other tests listed in the question, such as KOH prep and Wood's Lamp, are not used to diagnose herpes zoster.
Step-by-step explanation:
The test that confirms herpes zoster is the Tzanck test. The Tzanck test is a microscopic examination of cells taken from a blister caused by the virus. The cells are stained and examined under a microscope to identify characteristic features of the virus.
None of the other options listed in the question (KOH prep, Wood's Lamp) confirm herpes zoster. KOH prep and Wood's Lamp can be used to diagnose other skin conditions, but not specifically herpes zoster.