Blood Systems Trypanosoma cruzi and Chagas Disease Studies and Potential Strategies for Targeted Testing of Donors Blood Products Advisory Committee CBER FDA April 26, 2007. Michael Busch Brian Custer. Outline. BSRI/BSI T. cruzi & Chagas’ studies Test performance evaluation study
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Blood Systems Trypanosoma cruzi and Chagas Disease Studies and Potential Strategies for Targeted Testing of DonorsBlood Products Advisory CommitteeCBER FDAApril 26, 2007
Hypothesis: T. cruzi seropositive donors will have an overall 10% to 20% increased rate of cardiac and gastrointestinal symptoms and ECG abnormalities relative to control donors, and the frequency of symptoms and signs will correlate with duration of infection and PCR positivity.
Hypothesis: T. cruzi seropositive donors who are negative for parasitemia by PCR will demonstrate lower level antibody reactivity than PCR positive donors, and the reactivity levels will decline over time in the PCR-negative group.
Hypothesis: In contrast to T. cruzi seropositive donors in which T. cruzi PCR will be positive in greater than 70% of subjects, parasite DNA will not be detected in ELISA negative donors from either endemic or non-endemic regions.
Ortho®T. cruzi ELISA Test SystemPre-clinical Sensitivity
Sensitivity = 99.7% (753/755)1
Confirmed Negative by RIPA
1 Specimens from 12 Latin American countries
10,192 sequential donations from blood donors residing in the El Paso, Texas areaOrtho®T. cruzi ELISA Test SystemPre-clinicalSpecificity
Specificity - 100% Seroprevalence - 3/10,192
Tobler et al Transfusion, 2007
Cases: 500 blood donors who tested T. cruzi AB positive 6 – 10 years ago (using tests other than the US approved Ortho test)
Controls: 500 blood donors who tested T. cruzi Ab negative from the same blood center 6 – 10 years ago, matched on gender, age (+/- 5 years), and repeat versus first time donor status
Repeat reactive index donation results lead to:
T. cruzi ELISA, RIPA, and PCR testing
Other infectious agents:
Leishmania, Plasmodium, Paracoccidioides?
All United Blood Services prospective donors asked to provide:
N – No
M – Mexico
C – Central America and/or South America
B – Both Mexico and Central and/or South America
Used to flag donations that should not be used for plasma components
Proposed strategies to model: