ImmunoCard STAT! cartridge antigen detection assay compared to microplate enzyme immunoassay and modified Kinyoun's acid-fast staining technique for detection of Cryptosporidium in fecal specimens

Abstract

Cryptosporidium species infect humans and a wide range of animals worldwide; outbreaks of cryptosporidiosis have been reported in several countries. Routine diagnostic methods may be insufficient to demonstrate the presence of these organisms. The study assessed the diagnostic accuracy of the antigen detection immuno-cartridge test, ImmunoCard STAT! (Meridian Bioscience Inc., Cincinnati, OH, USA), compared to the combined gold standard: modified Kinyoun's acid-fast technique confirmed with the microplate enzyme immunoassay (EIA) for the detection of Cryptosporidium in fecal specimens. Three hundred fifteen formalin-fixed stool specimens were submitted for testing. The Kinyoun's acid-fast-stained smear revealed 24 positive samples for Cryptosporidium (of which 23 specimens were confirmed by the EIA) and 291 negative samples (of which 289 were negative by EIA). Agreement between the three used tests was shown in 22 positive and 288 negative samples for Cryptosporidium. Kappa score of agreement between the immuno-cartridge test and EIA was 0.957, p = 0.000. The sensitivity of the immuno-cartridge test was 96% (95% confidence interval (CI), 87% to 104%) and the total accuracy of the test was 97% (95% CI, 93-103). The ImmunoCard STAT! Cryptosporidium cartridge assay is easy to use and does not require specialized training or equipment and is useful in routine diagnosis and screening for Cryptosporidium especially where rapid, point of care testing is needed or where other reliable tests are unfeasible with a performance comparable to the EIA and acid-fast technique.

Enteric Protozoa in the Developed World: a Public Health Perspective

“…The modified ZiehlNeelsen technique (413) is used widely; however, one recent study found that it was less sensitive than PCR (75.7%; 95% CI ϭ 68.3 to 81.8%) but was highly specific (100%; 95% CI ϭ 96.5 to 100%) (56). Kinyoun's acid-fast staining technique (102), modified Sheather's flotation technique (76,294,296), and the iron-hematoxylin staining technique (119) have also been described.…”

Molecular genetic characterization of human Cryptosporidium isolates and their respective demographic, environmental and clinical manifestations in Egyptian diarrheic patients

“…Such conflicting evaluations reduce the advantage of rapid detection of Cryptosporidium by ICT immunoassay, which may be explained by the persistence of antigens for several days after treatment, or an abortive infection, or by cross-reaction with other antigens [42] . It was reported that several mAbs against oocysts antigens of C. parvum cross react with other parasitic life cycle stages, other Cryptosporidium species or other coccidian parasites [43,44] . Because reaction of the immuno-card test may persist after the patient stops shedding intact organisms, our results may not be false-positive but may rather represent recently cured cases [45] .…”

Community Laboratory Testing for Cryptosporidium: Multicenter Study Retesting Public Health Surveillance Stool Samples Positive for Cryptosporidium by Rapid Cartridge Assay with Direct Fluorescent Antibody Testing

“…Several studies have previously identified these tests as having sensitivity and specificity similar to the performance of DFA, the gold standard test for Cryptosporidium [18–20]. However, previous problems with false-positive results associated with these tests have been noted [19, 24, 25].…”

“…When exposed to fecal specimens with Cryptosporidium antigen, a cartridge containing proprietary capture antibody for the antigen will cause a colored line (Remel Xpect, red for Cryptosporidium ; Meridian Immunocard STAT!, gray-black) to appear in addition to a line in the control window. In previous studies, these assays were reported to perform well compared to other diagnostics assays [18–20]. …”