ELISA for detection of anti-Giardia specific IgM: response in serum

Infection with Giardia lamblia (G. duodenalis, G. intestinalis) is common all over the world, especially in children. Traditional diagnosis by faecal microscopy has only moderate sensitivity; serological tests, although not always positive, are acceptable to patients and useful in epidemiological studies. We show here that serum IgM separated by column chromatography and assayed by an indirect ELISA test can be a useful tool for the diagnosis of giardiasis. One hundred and thirty-nine positive sera (based on a single faecal examination), and 97 negative serum samples from Riyadh, Saudi Arabia, were examined. Taking positive results as being 2 s.d. above the mean of the controls, there were 117 positive results among the microscopically negative controls (3% false positives). The sensitivity of the test was 84% and the specificity 97%; the predictive value of a positive result is 97.5% and of a negative one 81%.