# Presentation: 164098

## 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
- 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

**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)

- 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)

## Slide 5

## Slide 6

## Evidence of Sero-reversion

## Ortho® T. cruzi ELISA Test SystemPre-clinical Sensitivity

- Cutoff

- Confirmed Negative by RIPA

- Sensitivity = 99.7% (753/755)1

- 1    Specimens from 12 Latin American countries

- Ortho® *T. cruzi* ELISA Test SystemPre-clinical Sensitivity

## Ortho® T. cruzi ELISA Test SystemPre-clinical  Specificity

*Tobler et al Transfusion, 2007*

- Ortho® *T. cruzi* ELISA Test SystemPre-clinical**  **Specificity

**Specificity - 100%         Seroprevalence - 3/10,192**

## Slide 10

## 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

## 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

- 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

- REDS II International – Brazil Chagas Study

## 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

- 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

- 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 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

- 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

- 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 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

## Race/Ethnicity

| Group | Repeat
Number (%) | First Time 
Number (%) |
| --- | --- | --- |
| African American/Black | 1,772 (2.5) | 1,098 (5.8) |
| Hispanic/Latino | 8,710 (12.4) | 4,199 (22.1) |
| Native American | 671 (1.0) | 300 (1.6) |
| Asian/Pacific Islander | 768 (1.1) | 338 (1.8) |
| Caucasian/White | 55,200 (78.8) | 12,187 (64.0) |
| Other/Missing | 2,968 (4.2) | 907 (4.8) |

## Country of Birth 

| Country | Repeat
Number (%) | First Time 
Number (%) |
| --- | --- | --- |
| USA | 46,469 (66.3) | 13,512 (71.1) |
| Mexico | 748 (1.1) | 599 (3.2) |
| Central or South America | 150 (0.2) | 83 (0.4) |
| All other countries | 1,234 (1.8) | 354 (1.9) |
| Refused | 9 (0.01) | 4 (0.02) |
| Missing/Unknown | 21,479 (30.6) | 4,463 (23.5) |

## Responses to 1R

| Donor: 3 months or more in Mexico, Central or South America | Repeat
Number (%) | First Time 
Number (%) |
| --- | --- | --- |
| Mexico | 1,196 (1.4) | 860 (3.4) |
| Central/South America | 534 (0.6) | 234 (0.9) |
| Both Mexico and Central/South America | 118 (0.1) | 40 (0.2) |
| No  | 85,277 (97.8) | 24,425 (95.4) |
| No Response | 51 (0.06) | 30 (0.1) |
| Unknown/Unsure | 38 (0.04) | 6 (0.06) |

## Responses to 1S

| Donor’s Mother: 3 months or more in Mexico, Central or South America | Repeat
Number (%) | First Time 
Number (%) |
| --- | --- | --- |
| Mexico | 1,221 (1.8) | 935 (5.0) |
| Central/South America | 350 (0.5) | 153 (0.9) |
| Both Mexico and Central/South America | 34 (0.05) | 17 (0.09) |
| No  | 67,710 (97.5) | 17,051 (93.7) |
| No Response | 27 (0.04) | 31 (0.09) |
| Unknown/Unsure | 128 (0.2) | 75 (0.3) |

## Responses to 1T

| Donor: Travel to Mexico, Central or South America since last donation | Repeat
Number (%) |
| --- | --- |
| Mexico | 3,425 (5.0) |
| Central/South America | 248 (0.4) |
| Both Mexico and Central/South America | 44 (0.06) |
| No  | 65,155 (94.5) |
| No Response | 30 (0.04) |
| Unknown/Unsure | 28 (0.04) |

## 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

- 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

## First Time Only Targeted Testing in Europe (as of 2003)

| Country | Anti-HTLV | Syphilis  | Anti-HBc |
| --- | --- | --- | --- |
| Belgium |  |  | Y |
| Denmark | Y |  |  |
| Finland | Y |  |  |
| Luxembourg |  |  | Y |
| Norway | Y | Y | Y |
| Sweden | Y | Y | Y |

## 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 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:

## Slide 30