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

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.