Casoni skin test

Last revised by Bahman Rasuli on 9 Mar 2021

The Casoni skin test is a hypersensitivity based skin test used to detect hydatid disease. Although once a major test in diagnosing hydatid disease it has largely been superseded by newer more sensitive, specific and safer serological tests.

Sterile fluid (0.25 mL) of hydatid cyst origin is injected into one arm whilst 0.25 mL of normal saline is injected into the other arm to act as a control 1. Care must be taken as there is a risk of an anaphylactic reaction.

Observation of a wheal at the site of injection of the hydatid cyst origin fluid at 30 minutes post-injection is regarded as a positive test 1. Observation of a delayed reaction is also possible.

The test is only 63.8% sensitive and 47% specific to hydatid disease 2

The test was first described by Italian physician Tomaso Casoni (1880-1933) in 1912 2.

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