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 Although once a major test in diagnosing hydatid disease it has largely been superseded by newer more sensitive, specific and safer serological tests.
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Technique
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.
Findings
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.
Interpretation
The test is only 63.8% sensitive and 47% specific to hydatid disease 2.
History and etymology
The test was first described by Italian physician Tomaso Casoni (1880-1933) in 1912 2.