The use of enzyme linked immunosorbent assay (ELISA) and direct fluorescent antibody (DFA) methods for diagnosis of Giardia intestinalis.

The aim of this study was to evaluate the value of the direct fluorescent antibody (DFA) techniques reported to have high sensitivity and specificity and the enzyme linked immunosorbent assay (ELISA) test used to determine antigens in stool samples in the routine diagnosis of Giardia intestinalis. When 44 stool samples in which G. intestinalis cysts and/or trophozoites had been seen during native Lugol examination were investigated, positivity detected with the trichrome staining method, monoclonal ELISA method and monoclonal DFA method was found to be 37 (84.0%), 39 (88.6%) and 35 (79.5%) respectively. DFA detected Crytosporidium parvum cysts in addition to G. intestinalis in one sample. Twenty-seven (61.4%) of the samples were positive with all three methods. When compared with the DFA method, the ELISA method had a sensitivity of 88.6%, a specificity of 88.8%, a positive predictive value of 79.5% and a negative predictive value of 20.0% while the trichrome staining method had a sensitivity of 85.7%, a specificity of 77.8%, a positive predictive value of 81.1% and a negative predictive value of 22.2%. There was no statistically significant difference between the DFA and ELISA tests and between the DFA test and the trichrome staining method for diagnosing G. intestinalis (p > 0.05).