Author:

Keywords:

1103 Clinical Sciences, 1117 Public Health and Health Services, Microbiology, 3202 Clinical sciences, 3207 Medical microbiology

Abstract:

Objectives: Giardiasis is a diarrhoeal illness caused by Giardia lamblia, a one-celled parasite that lives in the intestine of humans and animals. The disease is diagnosed by microscopical identification of cysts or trophozoites in faeces, using direct mounts as well as concentration procedures. Since these analyses are labour-intensive and require a skilled microscopist, antigen detection tests (direct fluorescent antibody (DFA), enzyme immunoassay (EIA) and rapid, dipstick-like tests) have been developed as alternatives. We have evaluated the performance of a commercially available one-step immunochromatographic membrane test using specific monoclonal antibodies against the cyst membrane antigens of G. lamblia, the Giardia-strip (CorisBioconcept). Methods: The test performance was evaluated with known positive (n = 18) and negative (n = 55) stool specimens for G. lamblia, tested by the standard ova and parasite (O&P) examination as the golden standard. Faeces with other parasites (8 Endolimax nana, 8 Entamoeba coli, 4 Entamoeba histolytica and 1 Ancylostoma) and Staphylococcus aureus (3) were included to evaluate the specificity of the test. These fresh and unpreserved samples, obtained from the laboratory of UZ Gasthuisberg and Medisch Centrum voor Huisartsen Leuven, were frozen and maintained at -20_C prior to testing. The Giardia-strip was used according to the manufacturer’s instructions. Results: By the Giardia-strip, 17 of the 18 known positive specimens were positive and 54 of the 55 Giardia-negative samples were negative (94.4% sensitivity, 98.2% specificity, 94.4% positive predictive value and 98.2% negative predictive value), compared to (O&P) which is considered as the reference method. The Giardia false-positive discrepant sample came from a patient who was on holiday in Tunisia. Microscopy on a control sample of the same patient remained negative. The missed positive specimen by the Giardia-strip contained many cysts. No cross-reactions with other parasites or S. aureus were observed in this study. Conclusion: The Giardia-strip has an excellent sensitivity and specificity for the detection of G. lamblia in stool. The test is easy to perform (no concentration prior to testing), suitable for single sample analysis and has a short turn-around-time (15 minutes). This diagnostic kit may be very beneficial in the absence of trained microscopists. However, it cannot substitute the routine O&Ps as only G. lamblia is detected.