Casoni test

The Casoni test is an immediate hypersensitivity skin test used in the diagnosis of hydatid disease introduced by casoni. The test involves the intradermal injection of 0.25 ml of sterilised fluid from hydatid cysts/human cyst and sterilised by Seitz filtration on forearm and equal volume of saline injected on the other forearm. Observations made for next 30 mins and after 1 to 2 days. A wheal response occurring at the injection site within 20 minutes is considered positive. (Immediate hypersensitivity). Delayed hypersensitivity reaction usually read after 18-24 hours. The test is positive in about 90% of cases of hydatid disease affecting the liver, but positive in less than 50% of patients with hydatid disease elsewhere in the body; false positive results are also common. Precaution – Being a type I hypersensitivity reaction, anaphylactic reaction tray must be kept ready before carrying out the test.Consequently, serological tests are now generally used.