Comparative sensitivity and specificity of the Casoni intradermal and the immunoelectrophoresis tests for the diagnosis of hydatid disease.

The Casoni intradermal (ID) test, using two antigens, was compared with the immunoelectrophoresis (IEP) test for diagnosis in 47 surgically confirmed cases of hydatid disease and 73 non-hydatid persons. An antigen prepared from boiled hydatid cyst fluid (HF) was markedly more sensitive in the ID test than another prepared from whole HF but both produced false-positive reactions in three persons with other disease conditions. The IEP test yielded no false positives and its sensitivity was similar to the ID test using the more sensitive boiled HF antigen. Some patients were ID-positive and IEP-negative and vice-versa. Diagnostic sensitivity of both tests varied according to the localization and condition of the cyst. A detectable immune response was more frequent in patients with liver cysts than in those with lung cysts. Regardless of cyst localization, lowest diagnostic sensitivity was observed in patients whose cysts were intact and of the hyaline type, whereas recently broken cysts were associated with the most consistently detectable immune response. The limitations of the ID test are discussed and it is suggested that, until more specific antigens are available, there appears to be little value in utilizing this test where the more specific serological techniques are available.