Immunochromatographic Test Detects Fecal Parasites

A recently developed test that detects three pathogenic protozoal parasites in human stool samples has been evaluated.

An immunochromatographic (IC) dip strip test simultaneously detects Cryptosporidium spp, Giardia duodenalis, and Entamoeba histolytica that are known to cause diarrheal disease.

At the University of Zaragoza (Spain) scientists collected 160 stool samples from patients with intestinal discomfort or diarrhea, in which parasitic infections needed to be ruled out. Samples were taken and analyzed by microscopic examination and by different IC tests, from July 2008 to December 2008. Fresh specimens were processed within 24 hours of collection. Besides the IC tests, both enzyme-linked immunosorbent assays (ELISA) and heminested polymerase chain reactions (PCR) were performed. Microscopy and PCR were the “gold standard” reference techniques and the results of the RidaQuick IC triple stool test were compared with those obtained with ELISA and IC single test for the three parasites.

Microscopic examination revealed that 22 samples were diagnosed as positive for Cryptosporidium spp., 31 for Giardia duodenalis, 41 for Entamoeba histolytica/dispar, and 68 had a negative diagnosis for the three parasites. Results of RidaQuick IC tests (R-Biopharm; Darmstadt, Germany) show sensitivities of 70%-72% for Cryptosporidium, 90%-97% for Giardia and 62.5% for Entamoeba histolytica. Specificities for these three protozoa were 93.6%-94.9%, greater than 99% and 96.1%, respectively. In all diagnoses, agreement with microscopy and PCR was over 90%, except in the triple test and microscopy in E. histolytica detection that was 76.3%, due to the inability of microscopy to differentiate E. histolytica from nonpathogenic species such as E. dispar or E. moshkovskii.

The authors concluded that the triple stool immunoassays provide adequate sensitivities and specificities with clinically relevant cost-effectiveness. They can be used in outbreak situations, for screening proposals and for massive assays in endemic areas where a large number of samples must be analyzed or as complementary test for individual diagnosis since the entire test could be performed in 15–20 minutes. The study was published online on January 20, 2012, in the Journal of Clinical Microbiology & Infectious Diseases.

Related Links:
University of Zaragoza
R-Biopharm