The serological diagnosis of amebiasis by means of the precipitin test.

Abstract

Summary A simple and rapid precipitin test for significant clinical infection with Endamoeba histolytica is described. A drop of clear serum is mixed with a drop of clear antigen. A specific precipitate, observed by microscope, is the basis of a positive test. The test, as expected, is frequently negative in acute amebic dysentery and, desirably, it is often negative in the asymptomatic carrier state, permitting an exclusion of up to 50 per cent of individuals who harbor this parasite without symptoms. When tissue invasion has presumably occurred, in series other than acute amebic dysentery, the test has shown 85 to 100 per cent positive results in several series diagnosed as clinical amebiasis; 95 per cent positive results in one series of stool-positive persons who had recently gone through a severe epidemic and 5 out of 5 positive results in liver abscess cases. In serums which are clear initially, false positive results are virtually nonexistent. Certain principles and precautions in evaluating and using the test are stressed. More experience is needed, chiefly in the area of the sensitivity of the test in clinical disease of various types and degrees of severity, because as yet little work has been done in determining antibody response to different degrees of invasion of tissues by E. histolytica. Also useful to know, but yet to be determined, are the time of appearance of detectable antibody in new cases, and its persistence or time of disappearance after cure.