Commercial Assay for Detection of Giardia lamblia and Cryptosporidium parvum Antigens in Human Fecal Specimens by Rapid Solid-Phase Qualitative Immunochromatography

Abstract

The ImmunoCard STAT! Cryptosporidium/Giardia rapid assay (Meridian Bioscience, Inc.) is a solid-phase qualitative immunochromatographic assay that detects and distinguishes between Giardia lamblia and Cryptosporidium parvum in aqueous extracts of human fecal specimens (fresh, frozen, unfixed, or fixed in 5 or 10% formalin or sodium acetate-acetic acid-formalin). By using specific antibodies, antigens specific for these organisms are isolated and immobilized on a substrate. After the addition of appropriate reagents, a positive test is detected visually by the presence of a gray-black color bar (regardless of the intensity) next to the organism name printed on the test device. A control is included in the device. Steps include tube preparation (buffer, patient specimen, conjugates A and B), testing (addition of sample onto the test device), and visual reading (total time, 12 min). Test performance was evaluated with known positive and negative stool specimens (170 specimens positive for Giardia and 231 specimens negative for Giardia) (85 specimens positive for Cryptosporidium and 316 specimens negative for Cryptosporidium); they were tested with trichrome, ironhematoxylin, or modified acid-fast stains or the Meridian Bioscience, Inc., Giardia/Cryptosporidium Merifluor combination reagent; specimens with discrepant results were retested by using the Merifluor combination reagent. On the basis of the results of the reference methods, the sensitivities, specificities, and positive and negative predictive values were as follows: for G. lamblia, 93.5, 100, 100, and 95.5%, respectively; for C. parvum, 98.8, 100, 100, and 99.7%, respectively. False-negative results for G. lamblia were obtained with specimens with low parasite numbers (n ‫؍‬ 7) or specimens containing trophozoites only (n ‫؍‬ 3); one specimen with a false-negative result contained numerous cysts. The one specimen false negative for C. parvum was confirmed to be positive by immunofluorescence. No cross-reactivity was seen with 10 different protozoa (152 challenges), nine different helminths (35 challenges), or human cells (4 challenges) found in fecal specimens. This rapid test system may be very beneficial in the absence of trained microscopists; however, for patients who remain symptomatic after a negative result, the ova and parasite examination and special stains for other coccidia and the microsporidia should always remain options.With continued interest in rapid diagnostic testing, potential waterborne outbreaks, fewer well-trained microscopists, and expanding evidence that Giardia lamblia and Cryptosporidium parvum can cause severe symptoms in humans, laboratories are reviewing their test ordering options with regard to immunoassay kits that can be incorporated into their routine diagnostic protocols (3, 4, 6, 11-15, 19-22, 24). Revised recommendations related to ordering ova and parasite (O&P) examinations, the newer stool immunoassays, and special tests (stains) for coccidia and microsporidia have been developed and laboratories are incorporating...

Low sensitivity of the ImmunocardSTAT® Crypto/Giardia Rapid Assay test for the detection of Giardia and Cryptosporidium in fecal samples from children living in Libreville, Central Africa

“…infection compared to the 5.5 % found here (Minak et al 2012;Garcia et al 2003;Zaglool et al 2013). A high threshold for the detection of specific antigens is presumably in cause, accounting for the low sensitivity observed here, as sensitivities of 62 % to 81 % have been obtained, depending on parasite load in previous studies (Chartier et al 2013).…”

“…A higher value (68.0 %) was reported by one study in USA (Agnamey et al 2011). Using diarrheic samples of immunocompromised patients, higher values of this RDTs sensitivity have been noted, ranging from 70.0 to 94.0 %, in France, Saudi Arabia, California and Bangladesh (Garcia et al 2003. Agnamey et al 2011Minak et al 2012).…”

“…Antigens specific to G. duodenalis and C. spp. can be detected in fecal samples by immunochromatographic tests (ICTs) or rapid diagnostic tests (RDTs) (Garcia et al 2003;Minak et al 2012;Agnamey et al 2011;Stark et al 2014). In resource-limited settings, RDTs are highly suitable for point of care testing, with many advantages.…”

A Comparison of Microscopy and Enzyme Linked Immunosorbent Assay for Diagnosis of Giardia lamblia in Human Faecal Specimens

“…But, this problem has been overcome in direct detection of Giardia lamblia antigen in stool (Copro-antigen diagnosis) which was initially done by using counterimmunoelectrophoresis [15]. Now a days, the most widely used antigen detection immunoassays for Giardia are the direct fluorescent-antibody (DFA) tests which detect intact organisms, and enzyme immunoassays (EIAs) which detect soluble stool antigens [16,17]. The advantages of the EIA over DFA are that numerous samples can be screened at one time, and secondly the tests can be read objectively on a spectrophotometer instead of subjectively on a fluorescence microscope [18].…”

Recombinase Polymerase Amplification-Based Assay to Diagnose Giardia in Stool Samples

“…A number of nucleic acid-based and antigen-based diagnostic assays for stool sample detection of Giardia at the point-of-care are available and have shown impressive reliability. [9][10][11] Traditional nucleic acid diagnostics such as polymerase chain reaction (PCR), however, require the use of expensive thermal cycling equipment, limiting their use to central laboratories.…”