Diagnosis of giardiasis by specific IgM antibody enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was used to detect serum IgM and IgG antibodies against Giardia in fifty-two patients with diarrhoea from the United Kingdom and south India. Serum anti-Giardia IgM responses occurred in patients with giardiasis; in two of three patients studied longitudinally IgM levels had fallen to normal 2-3 weeks after treatment. At serum dilutions of 1/200 to 1/400 there was almost complete separation of ELISA readings between patients with Giardia and Giardia-free controls; the sensitivity and specificity of the ELISA were both 96%. Serum anti-Giardia IgG was detected in patients and controls but was unable to distinguish current from previous infection.