Serologic Testing for Trypanosoma cruzi : Comparison of Radioimmunoprecipitation Assay with Commercially Available Indirect Immunofluorescence Assay, Indirect Hemagglutination Assay, and Enzyme-Linked Immunosorbent Assay Kits

Abstract

The radioimmunoprecipitation assay (RIPA) has been used as a confirmatory test in several ongoing and published studies ofTrypanosoma cruzi in blood donors in the United States. Despite its use as a confirmatory test, few studies are available comparing RIPA to commercially available serologic test methods. Thus, we compared RIPA with two indirect hemagglutination assays (Biolab Diagnostica SA, São Paulo, Brazil; Hemagen Diagnostics, Inc., Waltham, Mass.) and four different enzyme-linked immunosorbent assays (Abbott Laboratories, Abbott Park, Ill.; Embrabio, São Paulo, Brazil; Organon Teknika, São Paulo, Brazil; and Gull Laboratories, Salt Lake City, Utah) using a panel of 220 serum specimens from Brazilian blood donors with a range of T. cruzi antibody titers as determined by indirect immunofluorescence assay (IFA). A titer of 1:20 was used as the baseline for seropositivity. All IFA-negative serum specimens (n = 19) were nonreactive on all tests. At a titer of 1:20 (n = 9), reactivity rates varied considerably among the tests, with only the RIPA and the Organon and Gull assays identifying reactive specimens. For specimens at a 1:40 titer (n = 35), most assays identified at least 32 of 35 (91%) specimens as reactive, but the Biolab assay only identified 24 (69%). At higher titers (1:80, n = 56; 1:160,n = 101) the assays were comparable, with the exception of the Biolab assay, demonstrating rates of agreement with IFA of ≥98%. Overall, when compared with several other test formats, RIPA demonstrated equivalent or superior rates of agreement with IFA-positive specimens across all titers examined. In particular, at titers of >1:40, the RIPA compared favorably with other test methods currently in use, supporting its application as a confirmatory test, particularly in a research setting.

Evaluation of a prototype Trypanosoma cruzi antibody assay with recombinant antigens on a fully automated chemiluminescence analyzer for blood donor screening

“…11 A highly sensitive and specific radioimmune precipitation assay (RIPA), which detects specific T. cruzi antibodies, was described almost two decades ago. 12,13 The RIPA has been suggested for use as a confirmatory test in the United States but its technical complexity, and the fact that it is labor-intensive, expensive, and involves radioactivity make its adoption for this purpose unlikely. In contrast, other serologic tests for detecting antibodies to T. cruzi are well suited for rapid and inexpensive diagnosis of the infection and have been in use widely in the endemic countries for decades.…”

Risk factors and select cardiac characteristics in dogs naturally infected with Trypanosoma cruzi presenting to a teaching hospital in Texas

“…The method of serological testing for T. cruzi in these dogs was an IFA performed by the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL, College Station, Texas), and samples with IgG titers of ≥20 were considered positive per TVMDL standard protocol; this cutoff has been used in dog and human studies. 7,26 In 3 dogs, no serologic testing was performed, but dogs were included in the analysis due to necropsy records indicating histopathological confirmation of intramyositic T. cruzi amastigotes. A positive serology result or histopathology diagnosis of Chagas disease qualified dogs as naturally infected for purposes of the analysis.…”

Trypanosoma cruzi in Los Angeles and Miami blood donors: impact of evolving donor demographics on seroprevalence and implications for transfusion transmission

“…All samples identified as repeat reactive by EIA underwent confirmatory testing at the ARC's Holland Laboratory (Rockville, MD) by using a radioimmunoprecipitation assay (RIPA). 20,21 These samples were assayed in parallel with three negative and three positive control sera, the latter obtained from parasitologically confirmed cases of Chagas' disease. Diagnostic confirmation of seropositivity by RIPA was defined as the presence of bands in autoradiographs indicative of antibodies specific for the 72-and 90-kDa glycoproteins of T. cruzi.…”