Evaluation of an enzyme-linked immunoassay for the detection of Cryptosporidium antigen in fecal specimens of HIV/AIDS patients

Cryptosporidium parvum, a protozoan parasite, causes severe diarrhea in immunodeficient hosts like HIV/AIDS patients, leading to significant morbidity and mortality. Diagnosis of the Cryptosporidium oocyst in the stool of these patients by conventional microscopy is labor intensive and time consuming. Therefore, we planned to evaluate the usefulness of a stool ELISA test in detecting Cryptosporidial antigen. About 89 stool specimens obtained from HIV-seropositive patients with diarrhea were subjected to an ELISA test and modified acid-fast staining (gold standard), on both direct and formol ether-concentrated specimens. The prevalence of Cryptosporidial diarrhea was found to be 12.4% (11/89). Other enteric pathogens detected were Isospora belli (3), Giardial cyst (3), Entamoeba coli cyst (2), and Entamoeba histolytica cyst (1). Dual infection with Cryptosporidium and Isospora belli was seen in two patients. Concentration technique improved identification by microscopy. The sensitivity and specificity for stool ELISA were found to be 90.9% and 98.7% respectively. The results of stool ELISA indicate that this simple, rapid, reliable, and standardized immunoassay test is sensitive and specific for routine diagnosis and may be useful for large-scale epidemiological studies of Cryptosporidiosis.