ABSTRACT
A double antibody sandwich ELISA technique using a chromatography purified anti sera against E. histolytica, G. lamblia and Cryptosporidium antigens was applied to detect coproantigens of the corresponding parasites in 90 patients. All positive cases were diagnosed by a parasitological examination and proved to have the infection. In addition to the 90 positive cases, 30 age-matched controls were included in the study, of which 20 individuals were infected with other parasites, but not Cryptosporidium, E. histolytica or G. lamblia [acted as an infected control group] and the other 20 individuals with no intestinal parasites [normal control group]. The assay could detect 100% of those infected with both of G. Lamblia and E. Histolytica and 96.6% of patients with Cryptosporidium infection. False positive reactions were detected in three cases using G. lamblia antisera [92.5%], five cases using E. histolytica antisera [87.5%] and two cases using Cryptosporidium antisera [95%]. A direct increase in the mean antigen level was observed with the increasing intensity of infection in the three parasites; so, higher mean OD reading was observed in the heavily infected cases than the moderately infected ones than lighter intensity of infection. Only those in the elder age group [>20 years] infected with E. Histolytica had statistically higher OD readings of the antigen than the middle age group [10-20 years]. On the other hand, no statistically significant difference was observed between the different age groups and antigen level in cases with either G. lamblia or Cryptosporidium