Diagnosis of giardiasis using an enzyme-linked immunosorbent assay (ELISA) on formalin preserved stools

From a total of 162 children, three stool samples were collected from each child over a period of one week and preserved in formalin. Giardia lamblia was diagnosed by direct microscopy of formol-ether concentrates for each of the three samples. The first sample was also subjected to an ELISA test for detection of Giardia Iambia stool antigen in formalin preserved stool specimens. Microscopic examination revealed that 45 children were infected whereas ELISA detected 41 cases giving a sensitivity of 91.1% and a specificity of 99.1%. Predictive value of a positive test was 97.6% and that of a negative test was 96.7%. A significant correlation was present between mean optical density readings of ELISA and number of cysts present. No crossreactivity was observed ELISA is a simple, sensitive and specific test that can be applied in epidemiological studies for detection of Giardia lamblia coproantigen in formalin preserved stool specimens.