Giardia diagnostic methods in human fecal samples: A comparative study

Abstract

Several methods were tried for Giardia detection in stool. This study aimed to compare between the results of ordinary microscopy, direct immunofluorescence assay (DIF), and flow cytometry (FC) for the detection of Giardia cyst in human stool samples. The study included 84 children recruited from outpatient clinics of Mansoura University Children Hospital. Fecal samples were processed and examined for Giardia cysts using conventional microscopy, DIF, and FC. Among 84 fecal samples, 40 (47.6%) were diagnosed as Giardia-positive by saline wet mount, while DIF and FC detected 52 (61.9%), and 38 (45%) Giardia-positive cases, respectively. When compared with DIF as a gold standard method, ordinary microscopy had 76.9% sensitivity and 100% specificity while the FC had a sensitivity of 73.1% and 100% specificity, with statistically significant differences between DIF and the other two methods (P < 0.05). DIF was able to detect as few as 500 cysts/g of concentrated stool, yielding a threshold higher than ordinary microscopy (1,800 cyst/g) even after concentration. It is concluded that direct microscopic examination is reliable in Giardia diagnosis as a first choice test. DIF is an excellent technique in clinically suspected cases after negative microscopy. FC was found to be less sensitive to obtain accurate organisms' count but it could be an effective alternative method for the detection of Giardia cysts, especially for large-scale epidemiological studies or extensive surveillance programs as it has the beneficial attribute of speed and do not depend on an experienced microscope viewer. However, DIF remains the gold standard while FC still requires significant technical improvements before it can compete with DIF for Giardia diagnosis. V C 2012 International Clinical Cytometry Society

Comparison of microscopy, ELISA, and real-time PCR for detectionof Giardia intestinalis in human stool specimens

“…The direct fluorescent antibody test and enzyme immunoassays (EIAs) have high sensitivity and specificity similar to the most widely used immunological techniques (18). EIA is practical when numerous samples should (19).…”

Diagnostic accuracy of two point‐of‐care kits for the diagnosis of Giardia species infection in dogs

“…This difference is difficult to explain considering that both tests are produced by the same manufacturer, employ the same technology and almost certainly use the same antibody for the detection of Giardia spp, although this type of information is not specified by the manufacturer and could not be obtained. The Single test has been developed for use in dogs and cats, whereas the Triple test has been designed only for dogs; therefore, we propose that the employment of potentially different antibodies and/or buffers or differences in the limit of detection between the two tests may account for the lower sensitivity of the Single kit (El-Nahas et al . 2013 ).…”

Issue Highlights—January 2013

“…The main aim of this study was to compare the results between standard light microscopy, direct immunofluorescence assay (DIF), and flow cytometry for the detection of Giardia cyst in human stool samples. From this analysis, ElNahas et al (27) concluded that a direct microscopic examination is reliable in Giardia diagnosis as a first choice test. However, DIF proved to be an excellent technique in clinically suspected cases after negative microscopy.…”