Evaluation of flow cytometry as a diagnostic method for detection of Giardia lambila in comparison to IFAT and other conventional staining techniques in fecal samples

ABSTRACT

Giardia lamblia is one of the most common diarrhea-related parasites in humans, where infection ranges from asymptomatic to acute or chronic disease. Because of the non-characteristic symptoms of giardiasis, as well as significant prevalence of cyst carriers, it is necessary to upgrade parasitological techniques for examination of feces, in order to avoid false negative results. Accurate diagnosis is important to exclude other parasitic causes of diarrhea. The present study is designed to assess the efficacy of flow cytometry [FC] as a sensitive method for detection of G. lamblia cysts in stool samples in comparison with other standard conventional diagnostic methods. 70 patients [30 males and 40 females] ranging in age from 5 to 60 years were included in this study. Stool samples were taken from each patient on three successive days to detect Giardia cysts and evaluate the intensity of infection. Different methods were used that included concentration methods, permanent stained slides, immunofluorescent antibody test [IFAT] and FC. Giardia lamblia cysts were detected in 24 samples by IFAT with detection rate of 34.3%. Using trichrome stain 20 samples [28.6%] were positive, modified Ziehl- Neelsen Stain [MZN] detected 11samples [15.7%], while Acridine Orange [AO] detected 14 positive samples [20%]. Flow cytometry detected 18 samples with detection rate of 25.7%. Sensitivity and specificity of FC were 90% and 100%, respectively and IFAT sensitivity and specificity were100% and 92%, respectively. Results of the present study clearly demonstrated that incorporation of IFAT and FC can improve sensitivity of detection of Giardia cysts in stool samples. Although FC is more expensive than the other staining methods and IFAT, it is rapid, simple and accurate in estimating the quantity of parasites in each sample. Thus, FC can be recommended for detection of protozoa in stool