Serologic testing for amoebiasis.

The diagnosis of amoebiasis presents problems, particularly if one relies on finding the organism. Thus, serologic tests are expedient. A gel diffusion precipitin test (GDP), commercially available, simple to perform, and inexpensive, was compared with the indirect hemagglutination test (IHA). 257 Patients' sera were tested; 14 had amoebic colitis, 21 had amoebic liver abscess, 63 had suspected amoebic liver abscess, and 46 had inflammatory bowel disease. GDP tests were positive in 85% of amoebic colitis and 95% of amoebic liver abscess patients; IHA was positive in 91% of amoebic colitis and 94% of abscess patients. Within 6 mo, GDP tests became negative in 66% of patients. IHA tests were observed positive up to 20 yr. The performance characteristics of diagnostic methods in amoebiasis, fecal examination, IHA and GDP, show serologic tests have superior sensitivity and predictive value in recognizing invasive disease.