Comparative performance of parasitological and enzyme immunoassay tests in the diagnosis of intestinal protozoan infections

ABSTRACT

Diagnosis of Entamoeba histolytica, Giardia lamblia and Cryptosporidium parvum depends on microscopic detection of their cysts, trophozoites or oocysts in faeces. The aim of this study was to evaluate the use of three enzyme immunoassay [EIA] kits namely, Entamoeba CELISA, Giardia CELISA and Crypto CELISA [all from Cellabs diagnostic, Australia] in detecting the above mentioned intestinal protozoans. It was also aimed to compare the performance of these immunoassay kits with microscopy examination tests [direct faecal wet smears, formalin-ether concentration, Gomori's trichrome stain and auramine-phenol staining] routinely performed in the diagnostic Microbiology Laboratory at Sultan Qaboos University Hospital. A total of 571 stool specimens were examined. Giardia CELISA and Crypto CELISA were found to be more sensitive and specific than microscopy. The sensitivity of both kits was 100% and the specificity was 99% and 95% respectively. The performance of Entamoeba CELISA kit could not be established due to the small number of E. histolytica positive specimens. The enzyme immunoassay tests were easy to run and read compared to the cumbersome, insensitive and labour intensive parasitological tests. The enzyme immunoassays may not replace the parasitological tests but may be used to confirm the clinical diagnosis of these parasites