Transcript Tests Used In Blood Screening (II) Test Performance; Optimal Use of Reference Panels David A.

Tests Used In Blood Screening (II)
Test Performance; Optimal Use of
Reference Panels
David A. Leiby, PhD
Head, Transmissible Diseases
WHO Consultation
27-28 January 2009
WHO Headquarters, Geneva
Holland Laboratory
Common Serologic Assays for T. cruzi
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




indirect immunofluoresence (IFA)
indirect hemagglutination (IHA)
ELISA
RIPA
Western/immuno blots
rapid tests*
* not used for blood screening
U.S./Canadian Transfusion Cases:
1987:
California - Mexican donor
1989:
New York City - Bolivian donor
Manitoba - Paraguayan donor
1993:
Houston - unknown donor
1999:
Miami - Chilean donor
2000:
Manitoba - German/Paraguayan donor
2002:
Rhode Island – Bolivian donor
Impact of Latin American Immigration
LA Seroprevalence: 1996-98
1/5,400
0.018
% Donors Positive
0.016
1/7,200
0.014
0.012
0.010
1/9,900
0.008
0.006
0.004
0.002
0.000
1996
1997
1998
Leiby et al., Transfusion 2002;42: 549-555
Models for Testing/Implementation
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


universal blood screening
 screening + confirmatory assays
 parallel testing (2-3 assays)
risk-factor models
 birth in endemic country
 lived in rural area, thatched roof, vector
exposure, etc.
immunosuppressed patients
 must identify recipients at greatest risk
test each donor only once/twice
 logistically complex
 needs cost/benefit analysis
 analysis of sensitivity
Current ARC Testing Algorithm
Index donation
T. cruzi Ab Testing
Repeat Reactive
Non-Reactive
Retrieve index frozen plasma or
index retention sample (IRS)
Defer donor and enroll in
Chagas follow-up study (CFS)
No Actions
Sample sent from
NTL for RIPA
Positive, Indeterminate, Negative
SSO collates test results
and sends reports
Chagas Follow-Up Studies
RIPA Positive Donor
Donor follow-up:
questionnaire
2 clot tubes
2 EDTA tubes
3 heparin tube
T. cruzi Ab Testing
RIPA
PCR
Hemoculture
SSO collates test results
and sends reports
Donor Management Practices in U.S.
 RRs notified/deferred
 supplemental testing encouraged
 no FDA licensed tests exists
 RIPA most sensitive test available
 donor counseling including donor follow-up
studies encouraged
 no donor reentry
 refer RIPA positive donors to physicians
 recipient tracing for RIPA positive donors
T. cruzi Reactive Donors (01/29/07-11/30/08)
25
21
16
9
9
31
52
219
41
12
6
80
4
13
37
39
464
8
39
115
25
64
DC
2
17
70
50
25
58
77
15
19
55
41
21
95
30
45
23
12
24
33
30
59
17.8 million donations screened
0.015% RR rate
RR from 46 states (-DE, RI)
RIPA pos (25%) from 38 states (+PR, DC)
60% from FL and CA (1:3700-1:7500)
Overall: 1:27,000
26
73
PR
29
35
343
Total Cases
RIPA Pos
RIPA Reported
2633
639 (25%)
2597
Continental U.S. Map: RIPA Positives (thru 11/30/08)
>80% from ARC/BSL
Total Repeat Reactive
RIPA Positive
RIPA Negative/Ind
RIPA Pending/NT
2989
735
2135 / 45
74
22 Month Experience – ARC
Donation Type
No. Screened
No. RIPA Positive
Prevalence
Total Donors
5,459,496
235
1:23,232
Allogeneic
5,046,741
225
1:22,430
Autologous
65,960
6
1:10,993
Pheresis
346,795
4
1:86,699
Total Donations
12,059,270
235
1:51,316
Allogeneic
10,666,437
225
1:47,406
Autologous
99,863
6
1:16,644
Pheresis
1,292,970
4
1:323,243
2,482,904 donors contributed 2,317,801 person years
(only intervals between donations that were tested were counted)
PCR/Hemoculture Results for RIPA Pos Donors
+
-
%
PCR
(EDTA)
22
106
17
Hemoculture
(Heparin)
9
105
8
11/1/2008
10/1/2008
9/1/2008
8/1/2008
7/1/2008
6/1/2008
5/1/2008
4/1/2008
3/1/2008
2/1/2008
1/1/2008
12/1/2007
11/1/2007
10/1/2007
9/1/2007
8/1/2007
First Time (n=250, 63.45%)
7/1/2007
6/1/2007
5/1/2007
4/1/2007
3/1/2007
2/1/2007
1/1/2007
12/1/2006
11/1/2006
10/1/2006
9/1/2006
8/1/2006
Donor Status
RIPA Confirmed Positive Donors (n=394)
18
Repeat (n=144, 36.55%)
16
14
12
10
8
6
4
2
0
Donor Demographics to 11/30/08
RIPA Pos (N=394)
~ FT donors 250 (63%)
~ RPT donors 144 (37%)
~ Male 212 (54%)
~ Female 182 (46%)
~ Country of birth (N=149)
◦ Mexico
◦ US
◦ El Salvador
◦ Bolivia
◦ Honduras
◦ Colombia
◦ Argentina, Guatemala
◦ Brazil
◦ Ecuador, Nicaragua
◦ Paraguay, Chile, Somalia
44
37
24
15
6
5
4
3
2
1
RIPA Neg/Ind (N=1490)
~ FT donors 414 (28%)
~ RPT donors 1076 (72%)
~ Male 898 (60%)
~ Female 592 (40%)
~ Country of birth (N=420)
◦ US
400
◦ India
3
◦ China, Germany
2
◦ Thailand, Taiwan, Cuba,
Hungary, New Zealand,
Barbados, Ecuador, Panama,
Ukraine, Venezuela, Canada 1
◦ Colombia
2*
*21-37 years in Colombia, 1/2 with ECG
irregularities and 1 with upper GI symptoms
Autochthonous Transmission Summary
 45 potential autochthonous cases identified from screening US
blood donors
 37 from the ARC
 7 appear to be likely cases
 5 parasitemic
 2 donors thoroughly investigated by CDC (MS)
 another 7 have other risk factors
 some may be false positive
 continued investigation needed to determine frequency and risk
factor (e.g., hunting, camping, time spent outdoors, etc.)
 US-derived T. cruzi (USTC) study participants CDC, ARC and
UBS
 additional questionnaire re risk; CDC and ARC IRB approved
RIPA Positive Donors
Prior Non-reactive/Untested Donations
30
RIPA pos (N = 24 )
RIPA neg/pend (N = 625 )
25
Cases
20
15
10
5
v9
v1
4
v1
9
v2
4
v2
9
v3
4
v3
9
v4
4
v4
9
v5
4
v5
9
v6
4
v6
9
v7
4
v7
9
v8
4
v8
9
v9
4
v4
n1
1
n1
6
n2
1
n6
n1
0
Testing Week (IND (n) Start 08/28/06, IVD (v) Start 01/29/07)
16 with prior S/CO values: 0.12-0.98
8 QNS or NT donations
5 with multiple prior negative donations
Unlikely to be true “incident” infections!
Test Performance
IND/clinical trial (28/08/06 -28/01/07)
 PPV = 32 RIPA pos/63 RR = 51%; pos in 2 states
 RR rate = 63/148,969 = 0.042%
 Prevalence = 32/148,969 = 1:4655
Nationwide screening (29/01/07-30/11/08)
 PPV = 639 RIPA pos/2597 RR RIPA tested = 25%;
pos in 38 states (+ PR, DC)
 60% from FL and CA (1:3700-1:7500)
 RR rate = 2597 RRs/>17.8 x 106 donations = 0.015%
 Projected prevalence = 1:27,000
Sensitivity of Universal Testing (Ortho ELISA PI)
860/861 = 99.88% (95% CI = 99.35% to 100.00%)
Proposed Chagas Reference Standard
 requirements
 must include T. cruzi I and II
 broad geographic reactivity
 pooled vs. neat?
 sensitivity in diluted samples
 targeted antibody titers
 stability over time
 specified characteristics
 1 medium reactive from south
 1 medium reactive from north
 1 clear negative
Importance of Global Reference Standards
 test validation
 quality control
 comparisons with other tests
Interested Parties
 test manufacturers
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
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 evaluate candidate antigens
 measure sensitivity
regulatory agencies
 determine analytic sensitivity
 reproducibility/proficiency
 compare assays
blood establishments
 assay evaluation
 quality assessment
research institutions
diagnostic centers
 facilitate comparison with other laboratories
 internal controls
Summary & Conclusions
 significant number of U.S. blood donors infected with T. cruzi
 639 confirmed positives
 nationwide distribution
 1:27,000 donors infected
 current test performance
 99.88% sensitivity
 25% PPV
 need for a global reference standard
 test validation
 quality control
 assay comparison
 reference standard characteristics
 broad geographic reactivity is critical
Acknowledgements
American Red Cross
 Susan Stramer, SSO
 Greg Foster, SSO
 David Krysztof SSO
 Rebecca Townsend SSO
 Megan Nguyen, HL
 Melanie Proctor, HL
 Ross Herron, West Div
 Pamela Kahm, West Div
 Norma Espinoza, West Div
 Kay Crull, West Div
Blood Systems Laboratories
 Sally Caglioti
 Frank Radar
 Larry Morgan