Detection of Giardia lamblia by Microscopic Examination, Rapid Chromatographic Immunoassay Test, and Molecular Technique

Background Giardia lamblia is a pathogenic intestinal flagellate transmitted by the ingestion of contaminated water or food with the cyst stage of the parasite. Giardiasis can cause severe acute diarrhea and malabsorption or may persist as a chronic infection. Effective treatment and control measures depend on proper laboratory diagnosis using diagnostic methods with high sensitivity and specificity. Objective To compare the sensitivity and specificity of direct smear, Ritchie sedimentation technique, two brands of rapid chromatographic immunoassay test, and real-time polymerase chain reaction (PCR) for the detection of G. lamblia in clinical human fecal samples. Materials and methods Unpreserved 100 stool specimens were collected in clean plastic containers and labeled with the patient's information and examined through light microscopy, immunochromatographic test (ICTs), and real-time PCR. Results Out of 100 fresh stool samples obtained from workers analyzed, real-time PCR targeting the SSU rRNA gene was able to detect Giardia deoxyribonucleic acid (DNA) in (42) samples followed by ImmunoCard STAT! (31) samples (Meridian Bioscience, Germany), direct smear (23) samples, CerTest (19) samples (Biotec, Zaragoza, Spain), and Ritchie technique (17) samples. Real-time PCR was the most sensitive for the diagnosis of G. lamblia in comparison to the other techniques. Conclusions All the techniques investigated were sensitive for the detection of G. lamblia in stool samples. Further studies are recommended using multiplex real-time PCR assay in order to increase the possibility of the presence or absence of the infection.