Evaluation of a new enzyme-linked immunosorbent assay for detection of Chagas antibody in US blood donors.
BACKGROUND
Chagas disease, caused by the parasite Trypanosoma cruzi, represents a serious blood safety problem due to increasing immigration from Latin America. The Food and Drug Administration recently recommended implementation of Chagas antibody screening for US donors as soon as a suitable assay is licensed. An anonymized preclinical study of a prototype T. cruzi lysate-based enzyme-linked immunosorbent assay (ELISA) developed by Ortho-Clinical Diagnostics was conducted.


METHODS
Two populations of specimens were evaluated: 1) 10,192 sequential donations from blood donors residing in the El Paso, Texas, area and 2) 178 specimens from South America which were presumptively positive for antibodies to T. cruzi and purchased from commercial vendors.


RESULTS
A total of 10,189 (99.97%) of the 10,192 screened donor specimens did not react, whereas 3 (0.03%) tested initially reactive. The 3 initially reactive specimens tested repeat reactive and were confirmed by radioimmunoprecipitation analysis (RIPA). Based on antibody profile analysis, 2 of the 3 Chagas-positive specimens were from the same donor. Observed specificity of the test was therefore 100 percent. Of the specimens from South America, 173 of 178 were reactive by the prototype ELISA. Of the 5 nonreactive specimens, all did not react by indirect fluorescence assay, but 4 were positive by RIPA. Therefore, calculated sensitivity of the ELISA was 97.7 percent (173/177).


CONCLUSIONS
These studies indicate that the prototype ELISA has excellent sensitivity and specificity for detection of antibodies to T. cruzi in donors. Moreover, among donations from a geographically selected collection region of the United States, observed seroprevalence was 0.03 percent.
Tobler
Leslie H
LH
Blood Systems Research Institute, San Francisco, California 94118, USA. ltobler@bloodsystems.org
Contestable
Paul
P
Pitina
Lubov
L
Pitina
Lubor
L
Groth
Holly
H
Shaffer
Shirley
S
Blackburn
Gary R
GR
Warren
Harold
H
Lee
Stephen R
SR
Busch
Michael P
MP
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D001782:Blood Donors; D014355:Chagas Disease / Q000276:immunology* / Q000469:parasitology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods* / Q000592:standards; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D015531:Radioimmunoprecipitation Assay; D012680:Sensitivity and Specificity; D016036:Seroepidemiologic Studies; D013020:South America; D013781:Texas; D014349:Trypanosoma cruzi / Q000276:immunology*; D014481:United States
D000913:Antibodies, Protozoan