Giardia intestinalis nowadays is recognized as the most common parasitological cause of diarrhea, with 280 million infections per year. Microscopic examination of faecal samples has the advantage of low cost and the ability to simultaneously identify other parasitic infections. However, analysis of single stool sample and the skill of the microscopist can affect the accuracy of detection. As an attempt to improve the sensitivity of laboratory diagnosis of giardiasis, the present study aimed to evaluate the diagnostic performance of different parasitological techniques (Mini Parasep, MIFC and direct smear) and to evaluate a novel antigen capture immunoassays based on IgG polyclonal antibody conjugated with nanoparticles (Nano graphene based Sandwich ELISA and Dot-ELISA) for detection of Giardia antigen in stool samples. A total of 96 human stool samples were collected and classified into three groups according to stool examination results, (GI), 61 Giardia infected patients, (GII), 20 samples collected from patients infected with other parasites and (G III), 15 healthy individuals (negative control). In the current study, Giardia antigen detection was carried out by several steps including preparation of Giardia antigen, production, purification and labeling of rabbit anti-Giardia IgG polyclonal
antibodies. The Mini Parasep was the best followed by MIFC and direct smear. The study demonstrated that Nano Sandwich ELISA was higher than Traditional Sandwich ELISA regarding sensitivity, PPV, NPV and diagnostic accuracy with statistically significant difference between them, while specificity in Traditional Sandwich ELISA was higher than Nano Sandwich ELISA. Dot ELISA and Nano Dot ELISA had the same sensitivity, while Dot ELISA was higher than Nano Dot
ELISA regarding specificity, PPV, NPV and diagnostic accuracy without significant difference. This means that the use of graphene nanoparticles improved the diagnostic testing of human giardiasis.