Evaluation of seven commercial antigen detection tests for Giardia and Cryptosporidium in stool samples

Abstract

Stool samples from patients with abdominal symptoms were used to evaluate different copro-diagnostic assays for the detection of Giardia and Cryptosporidium. Results from microscopical examination following conventional stool concentration and direct fluorescent-antibody methods were compared with various commercially available immunochromatographic and enzyme immunoassays. Of 220 samples, 45 were positive for Giardia and 17 for Cryptosporidium. For Giardia, the sensitivities obtained by Ridascreen Giardia, Rida Quick Giardia, Rida Quick Combi and Giardia-Strip were 82%, 80%, 80% and 44%, respectively. For Cryptosporidium, the sensitivities obtained by Rida Quick Cryptosporidium, Ridascreen Cryptosporidium, Rida Quick Combi and Cryptosporidium-Strip were 88%, 82%, 82% and 75%, respectively. The specificity of all tests was > or = 98%. Other intestinal parasites were present in 68 samples, but cross-reactions with other protozoan or helminthic parasites were not observed. Overall, the copro-antigen assays were less time-consuming and easier to perform, but were less sensitive than conventional microscopical methods. Thus, these tests might be a useful addition to, but not a substitute for microscopical methods in the diagnosis of travel-associated giardiasis and cryptosporidiosis.

Comparison of diagnostic sensitivity and specificity of seven Cryptosporidium assays used in the UK

“…The sensitivity of the RIDAQUICK ICLF assay (84.9 %) was lower than those of the EIAs and AP microscopy, but the CIs overlapped; however, this test was significantly less sensitive than IFM (97.4 %) ( Table 1). The sensitivity of the RIDAQUICK ICLF reported here is similar to that found by Weitzel et al (2006). mZN microscopy was significantly less sensitive than all other tests (Table 1); when mZN and ICLF were compared by a paired test of proportions, the difference was significant (P50.0016).…”

“…Using automated platewashing and -reading equipment and highly specific assays to confirm positive results, our results showed increased sensitivity and specificity for the ProSpecT EIA compared with those reported by Johnston et al (2003). However, as highlighted previously by Weitzel et al (2006), comparisons may also be influenced by the study population from which the samples are drawn, the study design -especially in the size and power of the study -and in the nomination of a gold standard, as a true standard is lacking. The requirement to confirm and resolve the genus (Cryptosporidium and/or Giardia) in combination assays adds assurance, and single assays should likewise be confirmed.…”

“…The requirement to confirm and resolve the genus (Cryptosporidium and/or Giardia) in combination assays adds assurance, and single assays should likewise be confirmed. This is especially important to eliminate false positives (Doing et al, 1999;Weitzel et al, 2006).…”

“…There have been many publications comparing diagnostic tests for Cryptosporidium and, whilst enzyme immunoassays (EIAs) require reduced labour time and microscopy skills (Garcia & Shimizu, 1997), the sensitivity and specificity when measured against immunofluorescence microscopy (IFM) varies among studies (Garcia & Shimizu, 1997;Weitzel et al, 2006). However, there has been no direct evaluation of all assays used routinely in the UK, where testing is common in clinical laboratories (Chalmers et al, 2010a).…”

Giardia duodenalis: NEW INSIGHTS ON AN ANCIENT PARASITE

“…Immunochromatography methods (IC, dipsticks) provide a faster and more convenient diagnostic alternative in feces with no preservative. Several studies have reported similar sensitivity of Giardia detection in feces through IF and ELISA, and noticeably greater than the sensitivity shown by IC, particularly in feces with low Giardia cyst count [9,[116][117][118]. Molecular methods have shown exquisite sensitivity and specificity.…”