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Screening for HBsAg and Anti-HBc in North American Blood Donors

Screening for HBsAg and Anti-HBc in North American Blood Donors. John Saldanha, Roche Molecular Systems SoGAT XXI, 28-29 May, 2009, Brussels, Belgium. . Background. HBV screening of blood donations introduced in 1970s (HBsAg)

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Screening for HBsAg and Anti-HBc in North American Blood Donors

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  1. Screening for HBsAg and Anti-HBc in North American Blood Donors John Saldanha, Roche Molecular Systems SoGAT XXI, 28-29 May, 2009, Brussels, Belgium .

  2. Background • HBV screening of blood donations introduced in 1970s (HBsAg) • In mid-1980s, anti-HBc testing introduced as surrogate marker for non-A, non-B (HCV) • Risk of transfusion transmitted HBV greater than HCV or HIV-1 • Pre-2006: • Risk 1:63,000 – 1:205,000 (mathematical modeling) • Average window period 59 days (range 37 – 87 days) • Although NAT testing for HIV-1 and HCV introduced in 1999, no requirement yet for NAT testing for HBV

  3. HBsAg and Anti-HBc Testing • HBsAg tests • GS HBsAg EIA 3.0 23 January, 2003 • Ortho HBsAg ELISA Test System 3 23 April, 2003 • Abbott PRISM HBsAg ChLIA 18 July, 2006 • Anti-HBc test • Abbott PRISM HBc ChLIA 13 October, 2005

  4. Background: Incidence of Acute HBV in US • 1990 – 2007: acute HBV incidence declined by 82% • 2007: 4,519 acute, symptomatic cases ((1.5 cases per 100,000 population) • Underreporting and asymptomatic cases → 43,000 new infections • Decline greatest amongst children <15 years • Introduction of vaccination of children against HBV MMWR, 2009;58 (SS-3)

  5. HBV Vaccination and Blood Screening • HBV vaccination rates • >50% among younger cohorts • >70% in blood donors in younger cohort • Vaccination rates may confound HBV testing results and modeling • ‘Breakthrough’ infections in vaccinated individuals • Asymptomatic, low viral loads • Risk of transfusion-transmitted HBV infection? R. Forshee, BPAC, April 2009

  6. Current Incidence and Residual Risk of HBV Infection Two methods for modeling residual risk • Based on incidence from newly identified seroconverters (repeat donor data used) • Incidence based on HBsAg positive/anti-HBc negative donors (yield donors) x window period (‘New strategy’) Assumption: HBV infectious dose of 1-10 virions/20 mL plasma Zou et al, Transfusion, In Press

  7. Residual Risk of HBV Infection: USA ARC data 1997 – 1999 1:86,000 – 1:110,000 2006 – 2008 1:280,000 – 1:357,000 Greatest reduction in 16 – 19 year old age group (HBV vaccination program target) 2008: 44% donors anti-HBsAg positive/HBsAg, anti-HBc negative Donors <29 years old highest rate of anti-HBsAg positivity (65%) Zou et al, Transfusion, In Press

  8. Residual Risk of HBV Infection: Canada Incident rate model (repeat donors) used 2001 – 2005 1:153,000 56% of donors vaccinated (~ 80% under age 30) O’Brien et al, Transfusion, 2007, 47:316-325 O’Brien et al, Transfusion, 2008, 48:2323-2330

  9. HBV NAT Testing of Blood Donors • Blood Products Advisory Committee (BPAC) meeting, 1st April, 2009 • Three currently FDA-licensed HBV NAT tests • Roche COBAS AmpliScreen test (pools of 24) April, 2005 • Chiron Procleix Ultrio test (IDT and pools up to 16) August 2008 • Roche cobas MPX test (IDT and pools of 6) December, 2008 • Recent advances in technology, automation, more sensitive tests → testing in smaller pools or IDT • Potential to detect window cases, occult HBV and vaccine breakthrough cases

  10. HBV PrevalenceLinauts et al., Transfusion, 2008 • COBAS® AmpliScreen HBV Test, pools of 24 →1:844,870 • cobas® TaqScreen MPX Test, pools of 6 & individual testing → 1:72,336 • Combined data (COBAS® AmpliScreen HBV Test, pools of 24; cobas® TaqScreen MPX Test, pools of 6 & IDT) • 3,451,815 donations tested from April 2002 - December 2008 • Yield: 5 samples MPX NAT reactive → 1:690,363 HBsAg negative anti-HBc negative (PRISM) • Follow up samples for 3 donors • Window case, vaccine ‘breakthrough’, chronic carrier

  11. HBV Prevalence: ARC • Procleix Ultrio test • ~3.7 million donors screened • 9 NAT yield cases • 8 detected in pools of 16 → 1:389,796 • 1 detected by IDT → 1:576,940 • Overall rate: 1: 410,540 • 3 window cases • 6 vaccine ‘breakthrough’ S. Stramer, BPAC, April, 2009

  12. Summary • Decrease in HBV prevalence due to vaccination program • Incident rate (HBsAg) • USA: 1:280,000 – 1:357,000 • Canada: 1:153,000 • HBV NAT yield • USA: 1:410,000 to 1:690,000 • Canada: 1: 730,000 (estimated)

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