Impact of Testing Strategies to Reduce Transmission Risk

for HBVRavi Reddy, M VermeulenSouth African National Blood Service (SANBS)29 July 2013

Overview of SANBS• SANBS is a private not for profit company operating on

a fee for service basis• Provides a vein to vein blood transfusion service in 8 of

the 9 provinces in SA.– WPBTS in Western Cape

• 807,000 units of blood collected annually (100% voluntary) – 2 800 units bled daily

• 2 testing centres - Johannesburg and Durban – Also test for Namibia BTS (ID-NAT as well)

• 7 blood processing centres• 82 blood banks serving > 600 hospitals and clinics.• SANBS is accredited with the South African National

Accreditation System (SANAS)– Specific laboratories are ISO 17025 accredited

HQ in Johannesburg

Donation Testing Strategy• Quality assured testing of each donation – EQAS and internal QC systems in place

• Serology is mandatory– Anti-HIV-1,2, anti-HCV, HBsAg– Quality assured testing with sensitive serology assays leads to

detection of most of the viral positive donations cost effectively

• Individual Donation Nucleic Acid Testing (ID-NAT) – Implemented in October 2005

– Primarily to reduce risk of HIV window period transmission but also HBV transmission as well

Rationale for ID-NAT in South Africa• HIV prevalence in blood donors 0.21%• HBV prevalence in Blood Donors is 0.1%• Implemented ID-NAT testing in October 2005

– ULTRIO® assay on the TIGRIS® platform for:– HIV-1 RNA– HCV RNA– HBV DNA

– Serology testing for anti-HIV, anti-HCV and HBsAg done concurrently

• Evaluated and implemented Ultrio Plus assay in May 2011 because of increased sensitivity for HBV detection in window period

Geographic Distribution of Chronic HBV Infection

HBsAg Prevalence

³8% - High 2-7% - Intermediate

<2% - Low

WHO

HBV 5 Year data

Code Active % New % Rejoined %Grand Total %

Donations 2967492 432064 399863 3799509

Concordant (NAT and HBsAg Pos) 232 0.008 3050 0.706 137 0.034 3419 0.090

ID-NAT only pos 217 0.0073 194 0.0449 65 0.0163 476 0.0125

HBsAg only pos 2 0.0001 124 0.0287 1 0.0003 127 0.0033

Grand Total 451 0.015 3368 0.780 203 0.051 4022 0.106

Hepatitis B Summary

• 476 NAT+, HBsAg negative donations detected in 5 years– Hundreds of cases of transmission via transfusion prevented

• ID NAT testing has had a significant positive impact on reducing risk of HBV transmission via blood transfusion

• However still a risk of non detection of very low viral load donations

• One confirmed HBV transmission on a donation that tested negative with routine serology and ID-NAT– Donor triggered look back as subsequent donation positive

• Ultrio Plus Assay evaluated and in 2010/11

Confirmed pre-ID-NAT WP transmission case

• Donor triggered look back – RBC• Platelet concentrate – Patient unable to be traced• Donor details

– 47 year old white male (low risk, regular donor)– 54 previous donations– Negative donation – 26/11/2008– Date of Transfusion – 10/12/2008– Positive donation – 26/01/2009

ID-NAT WP transmission case  Donor RBC recipient

  26-Jan-09 9-Apr-09 30-Mar-09*

S/CO HBsAg 1st screen 352 0.27 743S/CO HBsAg 2nd

screen 385   721S/CO HBsAg 3rd

screen 395   760

S/CO Ultrio 1st screen 15.3 13.3 14.3

S/CO Ultrio 2nd screen 15.6 12.8 14.2

S/CO Ultrio 3rd screen 14.9  0.12  15.7

S/CO dHBV 23.1 invalid 25.2

anti-HBc IgM   Pos Pos

anti-HBc total   Pos Pos

anti-HBs   Neg Neg

* 3.5 months after transfusion

Additional tests to Determine if Recipient infection caused by Transfusion

• Donor plasma index donation (26/11/08)– SANBS 3 out of 30 replicates positive– Gen Probe 7 out of 30 replicates positive with Ultrio Plus

• Phylogenetic analysis/sequencing– Donor and recipient – genotype A– Intra group nucleotide divergence

• Donor/recipient 0.31% (99.7% Shared Identity)

• Transmission by Blood Tranfusion confirmed

Ultrio, Ultrio Plus, TaqScreen Study performed

• Compare Sensitivity of NAT assays with a range of samples– 10 000 random samples– 40 HIV ID-NAT yield samples– 107 HBV ID NAT positive samples on Ultrio– HBsAg positive, HBV NAT negative samples– Other samples (HIV Window period transmission

sample and HBV window period transmission sample)

Proportion reactive per NAT option on 107 Ultrio HBV ID-NAT yield samples

NAT option

% reactive

p< 0.00001

p< 0.00001

p< 0.00001

P= 0.00015

tested in 6 replicates in each test option

Proportion HBV NAT reactive on WP* and OBI yield samples

NAT option

% reactive

Percent ID-NAT reactive on HBsAg+/Ultrio- yield samples

assay donaties

replicates

reactive

%

Ultrio 32 384 82 21,4%Ultrio Plus 32 384 241 62,8%

copies/ml*

*determined by probit analysis in Ultrio Plus against Eurohep standard

% reactive (12 reps)

  Ultrio Ultrio Plus increase p value

Donations 775444 789948  

pre-HBsAg WP 47 (1:16 499) 80 (1:9 874) 170% 0.005

post-HBsAg WP 10 (1:77 544) 17 (1:46 468) 167% 0.19

OBI 94 (1:8249) 162 (1:46 468) 172% 0.00004

HBV-NAT yield 151 (1:5204) 259 (1:3 050) 172% <0.00001

HBsAg positive 820 (1:946) 841 (1:939) 103% 0.89

HBsAg+/DNA- 38 (1:20 406) 16 (1: 49 372) 0.002

All HBV infections 971 (1:799) 1100 (1:718) 111% 0.016

HBV ID-NAT Yields – One year Data Ultrio (2010 vs. Ultrio Plus 2011)

1-10 10-100 100-1000 >1000

48

77

13 8

88

110

43

17

Ultrio Ultrio PlusP<0.01 P=0.15 P<0.001 P=0.16

HBV-DNA cps/mL

Viral load distribution in all HBV NAT yields detected by Ultrio versus Ultrio Plus

Estimated WP reduction with Ultrio and Ultrio Plus (14.5 vs 24.7 days; 1.7 fold)

days

cps/

ml

0 10 20 30 40 50 60 700.01

0.1

1

10

100

1000

10000

100000

1000000

10000000Ultrio HBsAg

WPeclipse Ultrio Plus HBsAg

Ultrio Plus

Start WP

ID50 3.16 cps/20 ml

Ultrio Plus 50% LOD 4.1 cps/ml

Ultrio 50% LOD 63 cps/ml

HBsAg S/CO=1 3000 cps/ml

14.5 days

24.7 days12.9 days

22.9 days

screening period

WP transmission

risk

Ultrio 1:27 000

Ultrio PLus 1:43 000

WP Ultrio

Probable OBI transmission caseDonor Recipient

Drawing date 25/1/12 11/4/12¥ 11/5/12 11/6/12 4/7/12¥ 31/1/13

Status RBC Issued Look back Follow up Follow upUltrio Plus S/CO Neg 15.3/15.5/15.1 15.6/14.9 Neg Pos

dHBV S/CO 22.7 negHBsAg Neg Neg Neg Neg Pos Neg

Anti-HBc IgM Neg Neg Pos Pos

Anti-HBc total Pos Pos Pos PosAnti-HBs titre <2 2.6 <10 284 IU/L

Viral load 1.6 cps/mL* 43 cps/mL

¥ 100 % homology of whole HBV genotype D genome sequence of donor sample 11/4/12 and recipient sample 4/7/12 (analysis kindly performed by Dr Marco Koppelman, Sanquin, Amsterdam)* Estimated from 5/20 reps Ultrio Plus reactive by probit analysis ( 5.1% probability of transmission estimated with ID50 of 316 virions)

Testing Strategy for Hepatitis B• Countries with high incidence/prevalence of HBV

need to carefully review algorithms for HBV testing and assay selection– Maximise safety and minimise product discard

• High prevalence countries– HBsAg and ID-NAT but not anti-HBc

• No discard of anti-HBc positive units (6-8% of products usable)• Majority of early and occult infections detected• Minimal risk of not detecting post HBV DNA window period

donations and some OBI’s• Ultrio Plus in ID-NAT format has significantly improved

sensitivity and reduced risk

Course of HBV markers and residual transmission risk with ID-NAT

Vermeulen et al, Transfusion 2012;52:880-892.

1st WP ~10 days (Ultrio Plus)

2nd WP < 1day (Ultrio Plus)

OBI transmission riskunknown

SANBS Algorithm for HBV Testing• ID-NAT and HBsAg testing• Concordant positive – confirmed• ID-NAT only (2 x U+ and dHxV)• Non repeat reactive – donation discarded, anti-

HBc and anti-HBs marker added – 0.12% of donations discarded (mostly false positive)– Donor not notified– When donor returns

• Additional tests performed• Blood can be used if all routine tests and anti-HBc negative

Algorithm for HBV Testing (cont’d)• ID-NAT repeat reactive (2 out of 4), serology

negative– Additional tests on plasma bag– Donor recalled and additional tests done– If confirmed positive defer donor– If deferral, medical division contacts and counsels

donor– If all tests on follow up donation negative (review

need for additional tests or re-instate)

HIV infections in six years of ID-NAT screening of 4,520,230 donations

7993 (96.5%)

HIV RNA +, anti-HIV– window period

228 (2.8%)

HIV RNA +, anti-HIV +concordant

HIV RNA –, anti-HIV + elite controller64 (0.77%)

HIV-RNA anti-HIV

82/228 (38.4%) HIV-Ag + • 59 in first time donors (0.71%)• 4 in lapsed donors (0.05%)• 1 in repeat donor (0.01%)*

136 HIV-Ag-, RNA+ infections avoided (1:33,237)

Impact of ID NAT on Blood Safety - HIV

• Significant positive impact on blood safety contributing to major public health success story– 136 ID- NAT positive, anti-HIV negative, p24 antigen negative donations

detected in 6 years of testing. – Without ID-NAT there would have been numerous HIV transmissions via

blood transfusion – Major public health success story– Increased collections by 95 000 units over 5 years and increased

confidence in the blood supply– Could increase Black donors from 7% to 31% of donor base over 5 years

• Since ID NAT implementation, no reported case of HIV transmission since October 2005– HIV prevalence in blood donors has increased (0.07% to 0.23%)– Highlights impact of ID-NAT on improving blood safety

Summary• Implementation of ID-NAT testing has resulted

in a significant increase in safety of the South African blood supply compared to previous testing strategy

• ID-NAT continues to interdict infectious donations that are missed in mini pool format

• SANBS evaluation and one year data confirmed that Ultrio Plus is more sensitive than Ultrio for HBV

Thank You