Diascopy is a test for blanchability performed by applying pressure with a finger or glass slide and observing color changes. It is used to determine whether a lesion is vascular, nonvascular, or hemorrhagic. Hemorrhagic lesions and nonvascular lesions do not blanch; inflammatory lesions do.

What is a positive diascopy?

1] It is used to determine whether a lesion is vascular (inflammatory or congenital), nonvascular (nevus), or hemorrhagic (petechia or purpura). Hemorrhagic lesions and nonvascular lesions do not blanch("negative diascopy"); inflammatory lesions do("positive diascopy").

What is diascopy used for?

Diascopy is used to determine whether erythema in a lesion is due to blood within superficial vessels (inflammatory or vascular lesions) or is due to hemorrhage (petechiae or purpura). A microscope slide is pressed against a lesion (diascopy) to see whether it blanches.