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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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michael busch brian custer

Blood Systems Trypanosoma cruzi and Chagas Disease Studies and Potential Strategies for Targeted Testing of DonorsBlood Products Advisory CommitteeCBER FDAApril 26, 2007

Michael Busch

Brian Custer

  • BSRI/BSI T. cruzi & Chagas’ studies
  • Test performance evaluation study
  • Clinical evaluation studies
  • Analysis of donor testing strategies
    • DHQ questions
    • Risk factors questions
    • Capacity for targeted testing
    • Formal decision analysis
  • Experience to date (Feb. 26 – April 7)
reds ii international brazil chagas study
REDS II International – Brazil Chagas Study
  • Aim A. Define the natural history of Chagas disease in T. cruzi seropositive blood donors, according to donor demographic parameters, time since donation and exposure, and presence of persistent parasitemia.

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.

  • Aim B. Characterize persistence of T. cruzi antibody reactivity over time, relative to detection of parasitemia by PCR.

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.

  • Aim C. Determine rate of seronegative T. cruzi infection by performing coded PCR on seronegative populations from endemic and non-endemic regions and seropositve controls.

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.

Data collected at each study visit
    • Patients’ medical history (baseline only)
    • Physical exam
    • Clinical tests (serology, ECG, chest x-ray, echo)
    • T. cruzi infection diagnosis based on serology (complement fixation, indirect hemagglutination, immunofluorescence, and EIA)

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

ortho t cruzi elisa test system pre clinical specificity

RIPA Positive

RIPA Negative

10,192 sequential donations from blood donors residing in the El Paso, Texas area

Ortho®T. cruzi ELISA Test SystemPre-clinicalSpecificity

Specificity - 100% Seroprevalence - 3/10,192

Tobler et al Transfusion, 2007

reds ii international brazil chagas study11
REDS II International – Brazil Chagas Study
  • Case control study design in Sao Paulo and Montes Claros

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

reds ii international brazil chagas study12
REDS II International – Brazil Chagas Study
  • Death index search
  • New blood testing to establish current infection status
  • Medical history, risk factor and symptoms assessment
  • Clinical assessment
    • Physical exam
    • ECG
    • Echocardiogram (potentially contrast)
  • NHLBI Division of Cardiology
    • Centralized reading of ECG and Echo
bsi follow up studies
BSI - Follow-up Studies

Repeat reactive index donation results lead to:

  • Donor symptoms and risk factors interview
  • Follow-up sample collection and testing

T. cruzi ELISA, RIPA, and PCR testing

Other infectious agents:

Leishmania, Plasmodium, Paracoccidioides?

  • Clinical evaluation study
bsi test performance evaluation
BSI - Test Performance Evaluation
  • Aims
    • 1a. Evaluate the performance characteristics of the T. cruzi ELISA based on index donation supplemental assays (RIPA, and Leishmania IFA for RIPA-negative and indeterminate cases), and assess risk factors and symptoms among all ELISA repeat reactive donors compared to non-reactive donors, as well as among repeat reactive donors relative to their RIPA/IFA confirmation status
    • 1.b. Confirm the T. cruzi infection status in index repeat reactive donors by obtaining a follow-up blood sample that will be tested by ELISA, RIPA, quantitative PCR and potentially a new recombinant T. cruzi antigen based antibody confirmation assay (LIPA)
bsi clinical evaluation
BSI - Clinical Evaluation
  • Aim
    • Begin to define the clinical stage and natural history of Chagas disease in T. cruzi seropositive U.S. blood donors according to:
      • Donor demographics
      • Estimated time since (last) exposure
      • Presence of persistent parasitemia
      • Establish a group of confirmed seropositve donors, based on RIPA and/or PCR positive results, that represent the basis for a long-term cohort and outcomes study
bsi clinical evaluation16
BSI - Clinical Evaluation
  • T. cruzi RIPA positive donors recruited
  • MD visit or referral to local clinic for:
    • Physical examination
    • ECG
    • Echocardiogram
  • Additional testing of aliquots from samples collected in follow-up study
    • Other markers of T. cruzi infection or cardiac damage
decision analysis study
Decision Analysis Study
  • Aim
    • Develop a decision analysis model based on the combination of donor questioning and donation laboratory screening strategies to determine if any targeted testing strategy can meet safety objectives and assess which strategies are:
      • Most effective
      • Most cost-effective
donor history questionnaire
Donor History Questionnaire

All United Blood Services prospective donors asked to provide:

  • Race and ethnicity – Starting 2 years ago
  • Country of birth – Added just before T. cruzi testing
  • Three additional questions – Added Feb. 26, 2007
    • 1R – Have you spent time that adds up to 3 months or more in Mexico, Central America or South America?
    • 1S – Has your mother spent time that adds up to 3 months or more in Mexico, Central America or South America?
    • 1T – Since your last donation have you traveled to Mexico, Central America or South America?
donor history questionnaire19
Donor History Questionnaire
  • For each of the three additional questions four responses options are included:

N – No

M – Mexico

C – Central America and/or South America

B – Both Mexico and Central and/or South America

  • Only results for 89,118 eligible allogeneic donors from February 26 – April 7, 2007 are presented in the following slides
donor compliance with dhq questions
Donor compliance with DHQ questions
  • 1,509 out of 89,118 (1.7%) allogeneic donors left these voluntary questions blank
    • 350 First time donors (1.8%)
    • 1,159 Repeat donors (1.6%)
information systems and laboratory capacity for targeted testing
Information Systems and Laboratory Capacity for Targeted Testing
  • CMV testing (separate inventories)
  • WNV testing (type of testing)
  • HLA considerations and expected special testing
    • Ever transfused?
    • Ever pregnant?

Used to flag donations that should not be used for plasma components

decision analysis
Decision Analysis

Proposed strategies to model:

  • No screening – the baseline comparator strategy
    • By including a no screening strategy we will be able to highlight the number of repeat reactive donors who are identified and the safety gain achieved using T. cruzi ELISA testing
  • Screening of first time donors who report travel to or lived in Latin America for 3 or more months (excludes screening of repeat donors)
  • Screening of all first time donors and only repeat donors with travel to Latin America since their last donation
  • After a defined period of screening of every donation (for example 1 year) one-time screening of each donor who presents to donate following the implementation of T. cruzi screening AND screening of donors who report travel to Latin America since their last donation
  • Ongoing screening of each donation from each donor
  • Other potential strategies or modifications to the above strategies?
decision analysis29
Decision Analysis

Next steps:

  • Sufficient data is not available at this time
    • Continue to collect DHQ data and donor testing results
  • Intend to capture and assess the importance of uncertainty in all aspects of T. cruzi testing
  • Disease progression model development: