Download Infectious disease screening of blood products for prevention of

Infectious disease screening of
blood products for prevention
of transfusion-transmitted
diseases
Roni J. Bollag
October 2005
§ 610.40 Test requirements.
(a) Human blood and blood components.
Except as specified in paragraphs (c)
and (d) of this section, you, an establishment
that collects blood or blood
components, must test each donation
of human blood or blood component intended
for use in preparing a product,
(i) Syphilis testing. In addition to the
including donations intended as a component
testing otherwise required under this
of, or used to prepare, a medical
section, you must test by a serological
device, for evidence of infection due to
test for syphilis under §§ 640.5(a), 640.14,
the following communicable disease
640.23(a), 640.33(a), 640.53(a), and
agents:
(1) Human immunodeficiency virus,
640.65(b)(2) of this chapter.
type 1;
(2) Human immunodeficiency virus,
type 2;
(3) Hepatitis B virus;
(4) Hepatitis C virus;
(5) Human T-lymphotropic virus,
type I; and
PROPOSED 24th edition of Standards for Blood Banks
(6) Human T-lymphotropic virus,
and Transfusion Services, for Comment Purposes (10/7type II.
12/7/05)
Testing for transfusion-transmitted diseases
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HBsAg
anti-HBc
anti-HCV
HCV RNA
anti-HIV-1/2
HIV-1 RNA
anti-HTLV-I/II
syphilis serology
WNV RNA
Historical perspective
• Pre-1985: syphilis, HBsAg
• 1985-1989: better HBsAg, HIV, HTLV,
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+ ALT, anti-HBc (surrogates for nonA, nonB Hep)
1990: added HCV, HIV-2, HTLV-II
1996: HIV p24 Ag testing
1999: HIV, HCV NAT
2004: WNV NAT
Hepatitis B
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transmitted through parenteral, sexual exposure
mean incubation time 90 days
50% of infections are symptomatic
1/500 infections are lethal
6 -10% of infections become chronic
vaccination makes donor anti-HBs+, HBsAg-, anti-HBcrisk of transmission 1/66,000
Hepatitis C
• Transmitted through parenteral (common) or sexual (rare)
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exposure
Most common chronic blood-borne infection in US with
~150,000 new cases/year.
~ 4 million infected in US
Most common transfusion-transmitted disease
Most common cause of liver transplants.
75% of infections become chronic
Latency of symptomatic liver disease can be decades
Antibody appears in serum 54 – 192 days post-infection
Risk of transmission 1/103,000
HIV
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First reports of transfusion-transmitted HIV in 1982
Blood product testing began in 1985
transmitted through parenteral, sexual exposure
Variable latency period
Antibody titer detectable ~ 45 days post-infection
Common symptoms include night sweats, weight loss,
diarrhea, thrush, purpura
• Infection chronic, but viral load abated with multi-drug
therapy
• Risk of transmission 1/563,000
Transfusion transmission risks
Transmission risk, per unit
1:100
HIV
1:1000
HBV
1:10 000
HCV
1:100 000
1:1 000 000
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
HTLV-I/II
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Transmitted through parenteral or sexual exposure
HTLV-I endemic in Japan and the Caribbean
Most infections generate only mild symptoms
HTLV-1 causes adult T-cell leukemia/lymphoma
(~0.1%/year)
neurological disorder similar to MS (~0.1%/year)
Risk of transmission 1/641,000.
West Nile Virus
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transmitted by arthropod exposure (incidental)
birds are primary hosts
50nm spherical, lipid-enveloped flavivirus
Single-stranded positive sense RNA genome (11,000 nts)
Encephalitis, meningites
Asymmetric flaccid paralysis (poliomyelitis-like)
2002: 4156 cases reported in U.S. (284 fatalities)
5-10 % mortality
Initial screening by questionnaire
Voluntary NAT testing: through 2004, 1017 units withdrawn
due to presumptive WNV infection
• Peak exposure in August-September
• Viremia 6.5 to 56.4 days
Syphilis
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“The great imitator”
transmitted by sexual exposure
rarely transmitted by transfusion (2-3 reports in 30 years)
seroconversion occurs after occurs after spirochetemia
untreated infection progresses through multiple stages
testing is required by AABB (past 50 years)
syphilis positivity considered surrogate marker for other
diseases transmitted by high-risk behaviors
• RPR for cardiolipin or reagin (non-specific)
• Positive RPR sent for treponemal antibody testing (specific)
Misperception?
“Syphilis is a venereal disease that can also be acquired by
exposure to infected blood.”
- introduction to eMedicine article
http://www.emedicine.com/MED/topic2224.htm
Trends in infectious disease
Cases per 100,000 Population
Syphilis
160
140
120
100
Series1
80
60
40
20
0
1940
1950
1960
1970
1980
YEAR
1990
2000
2010
RPR (non-treponemal)
• Antigen:
• 0.003% cardiolipin
• 0.02% lecithin
• 0.09% cholesterol
• 10% choline chloride
• 0.01875% charcoal
• specimen not heat-inactivated
• acceptable specimens: serum, plasma, cord blood
• unacceptable specimen: CSF
VDRL (non-treponemal)
• Antigen:
• 0.03% cardiolipin
• 0.2% lecithin
• 0.9% cholesterol
• specimen heat-inactivated
• acceptable specimens: serum, CSF, cord blood
• unacceptable specimen: plasma
FTA-ABS (treponemal)
• Antigen:
• suspension of Treponema pallidum (Nichols) extracted
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from rabbit testicular tissue
Sorbent:
• cultures of nonpathogenic Reiter treponemes
Detection
• FITC-labeled rabbit antihuman IgG
TP-PA = MHA-TP (treponemal)
• Antigen:
• formalinized tanned sheep erythrocytes sensitized with
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T. pallidum (2.5% suspension)
Sorbent:
• 0.5% sheep red cell membranes
• 0.25% bovine red cell membranes
• 0.1% rabbit testicular extract
• 0.125% sonicated Reiter treponeme
• 1% normal rabbit serum
Detection
• Agglutination
Sensitivities and Specificities of
Syphilis serology tests
Standard Status Nontreponemal Tests
Sensitivity (%) by Stage of Untreated Syphilis
Latent
Late
Specificity
Test
Primary
Secondary
VDRL
78 (74-87)
100
96 (88-100) 71 (34-94)
98 (96-99)
RPR
86 (77-99)
100
98 (95-100)
98 (93-99)
73
Nonsyphilis
Standard Status Treponemal Tests
Sensitivity (%) by Stage of Untreated Syphilis
Specificity
Test
Primary
Secondary
Latent
Late
Nonsyphilis
FTA-ABS
84 (70-100)
100
100
96
97 (84-100)
MHA-TP
76 (69-90)
100
97 (97-100)
99 (98-100)
Causes of false positive non-treponemal tests
Acute
Chronic
Hepatitis
Connective tissue / autoimmune diseases
Viral pneumonia
Immunoglobulin abnormalities
Measles
Narcotic addiction
Malaria
Aging
Pregnancy
Leprosy
Infectious mononucleosis
Malignancy
Chicken pox
Other viral infections
Immunizations
Drug use
Lab / technical error
Causes of false positive treponemal tests
FTA-ABS
MHA-TP
1% false positives
< 1% false positives
Systemic, discoid, druginduced lupus
Narcotic addiction
Aging
Other collagen vascular
diseases
Leprosy
IV drug abuse
Lyme disease
Infectious mononucleosis
Drug addiction
Collagen vascular diseases
Leprosy
Other miscellaneous conditions
AABB position on syphilis testing
STATEMENT OF THE AMERICAN ASSOCIATION OF BLOOD
BANKS
BEFORE THE BLOOD PRODUCTS ADVISORY COMMITTEE
September 15, 2000
Syphilis Testing
Presented by Louis Katz, MD
Chair, AABB Transfusion Transmitted Disease Committee
“AABB believes the requirement for performing
an STS on each whole blood donation can safely
be eliminated based on thirty years experience”
AABB position on syphilis testing
Rationale
• transfusion-transmitted syphilis not recognized in US for 30
years
• transmissibility of T. pallidum occurs before the STS is
reactive
• storage of blood components in refrigerators and improved
oxygen tension likely to prevent transmission of spirochetes
• from 1990 to 1997, 57% of 241,800 component recalls were
for incorrect syphilis testing
Serological vs NAT testing
• Window period (based on serological testing):
• HCV (80d)
• HBV (56 d)
• HIV (16 d)
• Window period (based on NAT)
• HCV (10-30 d)
• HIV (10 d)
http://www.moffitt.usf.edu/pubs/ccj/v6n5/dept5.htm
Algorithm for multiplex NAT screening
Syphilis NAT testing
• Published PCR targets:
• tpf-1
• BMP
• tmpA, tmpB
• 47-kDa protein gene
• 16S RNA
• polA
• Sensitivity:
• 200 organisms/ml
• gold-standard (RIT) detects 2 organisms/ml
Proposal for Treponema pallidum
diagnostic PCR based on the highly
conserved mutL gene
• Primers:
• forward: CTTGAAACGCAAATGCTCAA
• reverse: CCCTCGCTTCCTAACACAAG
• PCR product: 197 bp
• Rationale:
bacterial mutL homologs are conserved through to
humans and are essential for function
Serology vs NAT testing for
Treponema pallidum
• Window period for syphilis: 1 – 3 wks
• NAT testing can identify 50 organisms (decreasing window to
less than 1 week).
• The rabbit infectivity test (RIT), = "gold standard" test has a
detection limit of a single organism and can be used to confirm
T. pallidum infection
• requires access to an animal facility
• extremely time-consuming and expensive
• Minimum TAT 90 d
Problems with NAT testing for syphilis
• molecular biological expertise required
• special precautions to prevent cross-contamination
• commercially available NAT assays require more than 12
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hours to perform
the cost of each commercial NAT test is approximately 10
times that of the most expensive EIA test.
Conclusion: serological testing for
syphilis in blood products
Serological testing for syphilis in individual
donated blood products should be
eliminated or replaced with highly specific
and sensitive NAT testing, to be performed
in multiplex algorithm with other NAT
screens
Bibliography
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Orton, S.L., Liu, H., Dodd, R.Y., Williams, A.E. (2002) Prevalence of circulating Treponema pallidum DNA
and RNA in blood donors with confirmed-positive syphilis tests.
Transfusion. 42: 94-99
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Palmer, H.M., Higgins, S.P., Herring, A.J., Kingston, M.A. (2003) Use of PCR in the diagnosis of early
syphilis in the United Kingdom. Sex. Transm. Infect. 79: 479-483.
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Liu, H., Rodes, B., Chen, C.-Y., Steiner, B. (2001) New tests for syphilis: rational design of a PCR method
for detection of Treponema pallidum in clinical specimens using unique regions of the DNA polymerase I
gene. J. Clin. Microbiol. 39:1941-1946
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Harmening, D.M. (2005) Modern Blood Banking and Transfusion Practices, 5th ed. Philadelphia: F.A.
Davis and Co.
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Brecher, M.E., ed. (2002) AABB Technical Manual, 14th ed. Bethesda, MD: American Association of
Blood Banks.
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http://www.aabb.org/pressroom/press_releases/prbpacsyph091400.htm
http://www.moffitt.usf.edu/pubs/ccj/v6n5/dept5.htm
http://www.aabb.org/About_the_AABB/Stds_and_Accred/stdsproposedbbts24.pdf
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http://www.bloodbook.com/trans-tran.html
http://www.emedicine.com/MED/topic2224.htm
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=Nucleotide&list_uids=3322571&dopt=
GenBank