723. Cryptosporidium Detection in Preserved Stool Specimens: A Comparison Study of EIA, DFA, and Direct Microscopic Method

Abstract Background Cryptosporidium is an intestinal parasite that may cause diarrhea. Laboratory diagnosis largely relies on microscopic or immunology-based antigen detection. Direct fluorescent antibody (DFA) is considered the gold standard. Enzyme immunoassay (EIA) is an attractive alternative, but direct comparison studies for the performance together with the impact from different specimen preservation media are limiting. Methods We compared these three methods for the detection of Cryptosporidium oocysts (direct microscopic) or antigen (DFA or EIA) from stool samples preserved in either 10% buffered formalin, Cary-Blair/C&S, or Total Fix (MCC, Torrance, CA). The DFA from Meridian Bioscience (Cincinnati, OH) and the EIA using CRYPTOSPORIDIUM II (TechLab®, Blacksburg, VA) were performed according to the manufacturer’s instructions. The direct microscopic method was performed according to laboratory protocols, including direct wet mount, modified acid-fast stain, or permanent trichrome stain. Results A total of 140 samples, including 116 clinical specimens, 20 validation panel samples and 4 proficiency survey specimens, were examined (Table 1). The DFA and EIA methods produced 100% concordant results using all three preservatives, while the microscopic method had decreased sensitivity. All microscopic positives remained positive for both the DFA and EIA. Cross-reactivity from other parasites, such as Giardia, of the two immunoassays was not observed. Conclusion While the two immunological methods both outperformed the microscopic method, the EIA has the advantages of being objective, simple to perform, has less hands-on time, and thus makes it an attractive option for high throughput Cryptosporidium detection. Disclosures Kileen L. Shier, PhD, D(ABMM), MLS(ASCP)CM, Quest Diagnostics (Employee)


Cryptosporidium Detection in Preserved Stool Specimens: A Comparison
Background. Cryptosporidium is an intestinal parasite that may cause diarrhea. Laboratory diagnosis largely relies on microscopic or immunology-based antigen detection. Direct fluorescent antibody (DFA) is considered the gold standard. Enzyme immunoassay (EIA) is an attractive alternative, but direct comparison studies for the performance together with the impact from different specimen preservation media are limiting.

Methods.
We compared these three methods for the detection of Cryptosporidium oocysts (direct microscopic) or antigen (DFA or EIA) from stool samples preserved in either 10% buffered formalin, Cary-Blair/C&S, or Total Fix (MCC, Torrance, CA). The DFA from Meridian Bioscience (Cincinnati, OH) and the EIA using CRYPTOSPORIDIUM II (TechLab ® , Blacksburg, VA) were performed according to the manufacturer's instructions. The direct microscopic method was performed according to laboratory protocols, including direct wet mount, modified acid-fast stain, or permanent trichrome stain.
Results. A total of 140 samples, including 116 clinical specimens, 20 validation panel samples and 4 proficiency survey specimens, were examined (Table 1). The DFA and EIA methods produced 100% concordant results using all three preservatives, while the microscopic method had decreased sensitivity. All microscopic positives remained positive for both the DFA and EIA. Cross-reactivity from other parasites, such as Giardia, of the two immunoassays was not observed.
Conclusion. While the two immunological methods both outperformed the microscopic method, the EIA has the advantages of being objective, simple to perform, has less hands-on time, and thus makes it an attractive option for high throughput Cryptosporidium detection.
Disclosures Background. Part of an essential "toolbox" to eliminate Toxoplasma gondii infection is prompt recognition of acute infection acquired during gestation, in order to initiate treatment for congenital toxoplasmosis (CT). From conception to one month post-partum, screening seronegative pregnant women monthly for antibody to the parasite enables treatment that prevents trans-placental transmission of newly acquired maternal Toxoplasma, or that attenuates signs and symptoms of CT. Tests that are highly sensitive and specific-and that meet the other World Health Organization ASSURED criteria for diagnostics-are very useful for this kind of screening. Herein, we evaluated the accuracy of a test that meets these criteria-the LDBIO Toxoplasma These are criteria for ideal screening or diagnostic tests, as described in a September 2017 paper in the Bulletin of the World Health Organization. Our study focused mostly on sensitivity and specificity for the LDBIO immunochromatography test for IgG and IgM specific to Toxoplasma gondii.
Methods. Both parts of this study examined results generated by the LDBIO device-a point-of-care immunochromatography test for Toxoplasma IgG and IgM-using serum and whole blood samples. With whole blood, thirty microliters were collected using a glass micro hematocrit tube. With both sera and whole blood, samples were loaded into the well of the LDBIO device, which took 20 minutes to generate results. In the first part of this study, we summarized results from three published U.S. studies and added new data from an ongoing clinical trial at the University of Chicago Medical Center (UCMC). In the second part of this study, we compiled data on how the LDBIO device performed on a total of 69 samples from U.S. and French studies that had led to false positive results when tested with commercially available comparator tests. Four of these false positives came from the UCMC trial.