Comparative analysis of enzyme-linked immunosorbent assay and direct microscopy for the diagnosis of Giardia intestinalis in fecal samples.

Context: Giardiasis is one of the most common nonviral infections causing diarrheal illness worldwide. In this prospective cross-sectional study, we evaluated the RIDASCREEN ® Giardia kit for detection of Giardia intestinalis in stool samples and compared the results with direct microscopy.
Materials and Methods: A total of 360 fecal samples were collected. They were then processed by wet film, iodine preparation and an enzyme-linked immunosorbent assay (ELISA) kit to determine the presence of Giardia trophozoites and cysts. Statistical analysis was performed by sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy.
Results and Conclusion: Of the 360 cases, 17.2% samples were positive for Giardia by direct microscopy and 23.6% were found to be positive by ELISA (sensitivity ~97%), but specificity was ~92% only. Because of less specificity, we need to perform ELISA in congruence with direct microscopy, etc. Further studies need to be performed on a larger sample size using other molecular tests in order to get more accurate estimations.