1. CBER Chagas Serological Lot Release Panel Development
Hira L. Nakhasi, Ph.D.
Director, Division of Emerging and
Transfusion Transmitted Diseases,
OBRR/CBER/FDA

2. Challenge for Blood Products
Enhance Product Safety, Purity and Potency
Avoid Product Shortages & Major Increased Costs
and
Critical Path opportunities exist that could improve blood product safety, efficacy and availability while minimizing disruptions to the blood system

3. FIVE LAYERS OF BLOOD SAFETY
FDA’s approach is to optimize each safety layer:
1. Donor screening and deferral based on geographic, behavioral and medical risk factors (donor education, self deferral, donor interview)
2. Laboratory testing and deferral (HIV-1, HIV-2, HBV, HCV, HTLV-I, HTLV-II, WNV, Chagas, syphilis)
3. Deferral registries to prevent use of blood from deferred donors
4. Quarantine controls to prevent unit release pending verification of donor suitability
5. Investigation and correction of deviations

4. Impact on the US Public Health: Blood Safety and Availability
Millions of units are transfused annually
Risk of transmission of infectious disease agents through transfusion has been significantly reduced with the introduction of donor screening tests

5. Evolution of Testing and Deferral
What happens when an emerging pathogen threatens the safety of the blood supply?
We introduce deferral criteria based on epidemiologically determined risk factors (medical, geographic or behavior-related exposures) as an initial safety measure
Where feasible, tests are developed, but deferral is maintained as an overlapping safeguard
Test sensitivity and specificity generally improve. However, risk-based deferrals are usually retained as an overlapping safeguard, especially when data are lacking on the relative safety contribution of risk-based vs. test-based deferrals

6. Chagas Transmissions by Blood or Organ Donations: U.S./Canadian
1987: California – Mexican blood donor
1989: New York City – Bolivian blood donor
Manitoba – Paraguayan blood donor
1993: Houston – unknown blood donor
1999: Miami – Chilean blood donor
2000: Manitoba – German/Paraguayan blood donor
2001: Three organ recipients – Central American organ donor
2002: Rhode Island – Bolivian donor
2006: Los Angeles – Heart donor traveled to Mexico
Los Angeles – Heart donor born in El Salvador

7. Blood Screening ELISA Licensed
December, 2006 ORTHO T. cruzi ELISA Test System approved for use as a blood screening assay
Large blood centers implemented testing Feb FDA recommendations for implementation under consideration.
Pre-release testing of kit lots is CBER responsibility
CBER Lot Release Panel developed
Cross testing with manufacturers panels

8. T. cruzi Reactive Donors by State of Residence (01/29/07 – 01/14/09)
Total Repeat Reactive
RIPA Positive
RIPA Negative/Ind
RIPA Pending/NT
3071
749
2177 / 47 98 26 22 16 9 9 19 31 53 53
229 42 43 6 13 81 1 4 59 81 14 DC
119 65 16 27 2 38 37 17 39 8 73
482 52 26 21 96 31 24 26 46 12 35 PR 78 30 26 30
18.9 million donations screened
0.015% RR rate
RR from 47 states (-DE)
RIPA pos (25%) from 38 states (+PR, DC)
61% from FL and CA (1:3800-1:7600)
Overall: 1:27,600 (Source: AABB) 36 57
365
* 3 RIPA pos samples represent
multiple positives from auto donor
and cord blood

9. Epidemiology of T.cruzi infection among US blood donor
Confirmed positive (RIPA) donors:
25% US born
75% born in T.cruzi endemic countries
63% first time donors (increasing)
37% repeat donors (declining)
Potential autochthonous cases ~42
Chagas positive cases from 47 states
Look back has identified 0/88 of recipients*
All donors are long term chronic asymptomatic (low parasitemia)
Transfusions are rarely WB
L/B have few platelet Transfusions ( > probability to transmit than RBC)
*On going investigations for a few cases possible T-T but rare
No true seroconversions have been identified

10. Current Status of T.cruzi testing in the US
Continuation of universal blood screening for T.cruzi to have a better evaluation of epidemiology of the disease and performance of the tests.
Need for licensed confirmatory test for donor reentry
Blood established performed validation of selective testing strategy (STS) to chart future course of testing in the US
Public discussion of the STS

11. Standardization of Serological Testing for Chagas’ Disease
Validation and licensing of new tests
Analytical characteristics
Sensitivity, specificity and reproducibility
Clinical characteristics
Random donor specificity trial
Known positive and High risk sensitivity trials
Testing lot to lot consistency of licensed assays

12. T. cruzi Panel Development
Purpose
∙ Lot Release Panel to test lot to lot consistency
∙ Not a Reference Panel
∙ Not an International Standard
Objective
∙ Obtain T. cruzi positive specimens from various geographical locations.
∙ Emphasis on immigration patterns found in the
U.S. donor pool from endemic countries.

13. Geographic Distribution of Panel Members* 7%
0.1%
24%
1.2%
0.4%
9.8%
10.7%
30% 3%
3.9%
17.7%
11.7%
Geographic Distribution of Panel Members * * * *
*Endemic countries for CBER Panel
N%-WHO estimate of prevalence,
Global burden of Chagas’ disease in the year 2000 DRAFT
A Moncayo, F Guhl, C Stein. *

14. Preliminary Formulation of Panel
Obtained/Purchased positive units and tested neat for titers and co-infections
(e.g. HCV, HBsAg, HIV etc.)
Determined acceptable units for possible panel manufacturing
∙ Highest Titers
∙ Largest Volumes
∙ Geographical Variation

15. Preliminary Formulation of Panel con’t
Chose Acceptable Units from Following Areas ∙ Mexico, Argentina, Nicaragua, and Brazil
Tested at CBER/DETTD with Serial Dilutions until Non-Reactive
∙ Ortho T. cruzi ELISA Test System
Sent Serial Dilutions to Kit Manufacturers
∙ Ortho-Clinical Diagnostics
∙ Abbott Laboratories
Evaluate all results to construct final panel

16. Candidate CBER Lot Release Panel
10 Member Panel
2 Negatives
4 geographical units at 2 dilutions
∙ Consensus High Positive (S/CO >2.0)
∙ Consensus Low Positive (S/CO ~ 1.0)
500 ml Bulk, 500 ml for Final Vialing
Fill Volume 1.25 ml

17. Validation of Candidate Panel
CBER/DETTD Tested Final Vialing
∙ Ortho T. cruzi ELISA Test System
∙ Abbott PRISM Chagas
∙ Abbott Chagas Confirmatory Assay
Ortho-Clinical Diagnostics Tested
Abbott Laboratories Tested

18. CBER Panel Testing Results
Manufacturers Testing
CBER
Testing
Lot Release
Criteria
CBER and
Manufacturers
Testing*
Panel Member
Screening Test A B
Screening
Tests
Confirmatory
Test
1 (Negative)
0.163
0.183
0.169
0.220 -
Negative
2 (Nic. High)
1.776
5.782
1.784
5.720 +
Positive
3 (Mex. High)
1.647
3.512
1.650
11.430
4 (Arg. High)
1.184
1.524
1.006
1.580
+/-
5 (Braz. High)
3.141
7.018
3.244
6.900
6 (Negative)
0.134
0.198
0.132
0.200
7 (Nic. Low)
1.131
2.641
1.100
3.560
8 (Mex. Low)
0.800
1.861
0.944
3.660
9 (Arg. Low)
0.606
0.812
0.642
1.010
10 (Braz. Low)
2.336
3.782
2.396
3.740
*Lot release criteria for the Confirmatory test will be determined after testing additional lots

19. Summary
Selection of panel members guided by availability, antibody titer, geographic source of specimens and origins of US immigrant blood donor population.
Panel dilutions guided by multiple tests on two testing platforms.
4 panel members mandatory positive (S/Co >2)
4 panel members low positive/high negative (S/Co~1)
2 negative
Acceptance criteria for each panel member as negative, positive or positive/negative determined by multiple testing of the diluted specimens from final filled vials.

20. Acknowledgments Robert Duncan Steve Kerby Kori Francis Robin Biswas
Alain Debrabant
Leslyn Aaron
Karen Smith
Silvano Wendel- Brazil

21. CBER Lot Release Procedures
Manufacturer submits kit lot with testing data for FDA review
Manufacturer’s in-process test results
Manufacturer’s release panel results
Test results from 100 non-reactive specimens
Manufacturer’s results from CBER panel
CBER tests kit with CBER panel
CBER approves/fails release of kit lot