Serologic testing for Trypanosoma cruzi: comparison of radioimmunoprecipitation assay with commercially available indirect immunofluorescence assay, indirect hemagglutination assay, and enzyme-linked immunosorbent assay kits.
The radioimmunoprecipitation assay (RIPA) has been used as a confirmatory test in several ongoing and published studies of Trypanosoma 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.
Leiby
D A
DA
Transmissible Diseases Department, American Red Cross, Rockville, Maryland 20855, USA.
Wendel
S
S
Takaoka
D T
DT
Fachini
R M
RM
Oliveira
L C
LC
Tibbals
M A
MA
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D001782:Blood Donors; D014355:Chagas Disease / Q000175:diagnosis* / Q000469:parasitology; D004797:Enzyme-Linked Immunosorbent Assay; D019084:Fluorescent Antibody Technique, Indirect; D006386:Hemagglutination Tests; D006801:Humans; D015531:Radioimmunoprecipitation Assay; D011933:Reagent Kits, Diagnostic; D012698:Serologic Tests; D014349:Trypanosoma cruzi / Q000276:immunology*
D000913:Antibodies, Protozoan; D011933:Reagent Kits, Diagnostic