A microscopic and immunodiagnostic search for giardiasis in patients with gastrointestinal disorders.

Direct microscopy and an ELISA technique were used to determine the prevalence of Giardia lamblia and its antigen in stool samples from patients with Crohn's disease, ulcerative colitis, acute-onset diarrhoea, or dyspepsia. Cysts of Giardia lamblia were observed by microscopy of faeces from two of the patients with acute-onset diarrhoea and one with dyspepsia. Giardia antigen was detected in the faeces of five patients, including all three in whom cysts had been identified by microscopy. No evidence of giardiasis was found in any patient with Crohn's disease or ulcerative colitis. It is concluded that the ELISA can reliably distinguish giardiasis from a range of other gastrointestinal disorders.