Detection of a Giardia lamblia coproantigen by using a commercially available immunoenzymatic assay, in Belo Horizonte, Brazil

Abstract

SUMMARYIt is known that fecal examination to detect Giardia lamblia cysts or trophozoites produces a high percentage of false-negative results. A commercially available immunoenzymatic assay (ProSpecT Giardia Microplate Assay, Alexon, Inc., BIOBRÁS) to detect G. lamblia specific coproantigen was evaluated for the first time in Brazil. A total of 90 specimens were tested. Each specimen was first tested as unpreserved stool, and then it was preserved in 10% Formalin to be tested 2 months later. The assay was able to identify all the 30 positive patients (sensitivity = 100.0%) by visual or spectrophotometric examination in the unpreserved specimens and was negative in 57 of the 60 patients without G. lamblia (specificity = 95.0%). The assay identified 27 of the 30 positive patients (sensitivity = 90.0%) and was negative in 59 of the 60 negatives (specificity = 98.3%) in the preserved stools according to both readings. A marked difference was observed in the optical densities in both groups, preserved and unpreserved stools, when the G. lamblia-positive specimens were compared to the negative or positive for other intestinal parasites than G. lamblia. The assay seems a good alternative for giardiasis diagnosis, especially when the fecal examination was repeatedly negative and the patient presents giardiasislike symptoms.

Freqüência de enteroparasitas em amostras de alface (Lactuca sativa) comercializadas em Lavras, Minas Gerais

“…Apesar do ensaio imunoenzimático apresentar uma alta sensibilidade e especificidade na detecção de coproantígeno de G. lamblia em amostras fecais 7 , provavelmente devido à metodologia empregada, não se atingiu o mesmo resultado testando amostras de alface.…”

Detection of Giardia duodenalis antigen in human fecal eluates by enzyme-linked immunosorbent assay using polyclonal antibodies

“…The sensitivity of these methods has varied from 88 to 98% with CIE, and from 68 to 100% for the ELISA; their specificity has ranged from 90 to 97% for CIE, 81-100% for ELISA, and 100% for dot-ELISA. Several Giardia antigen detection kits are now commercially available (Rosoff et al 1989, Addiss et al 1991, García & Shimizu 1997, Aldeen et al 1998, Rocha et al 1999, Fedorko et al 2000, their sensitivity varying from 85 to 98% and their specificity ranging between 90 and 100%. However, it is well known that the sensitivity and specificity of diagnostic methods based upon Giardia antigen detection can be affected by the genetic variability of Giardia isolates present in a given geographic area (Faubert & Belosevic 1990).…”

Comparison of two methodologies for detection of Giardia spp. cysts and Cryptosporidium spp. oocysts in activated sludge samples from a sewage treatment plant in the city of Campinas, São Paulo State, Brazil

“…prevalence rates range from between 13.8 and 63.3% for children (Rocha et al 1999). Another reason for the high concentrations found, could be the fact that in Campinas only 37% of the sewage was treated and discharged into the water bodies, contributing to source contamination (SANASA 2006).…”