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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) In mid-1980s, anti-HBc testing introduced as surrogate marker for nonA, 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 HBsAg and Anti-HBc Testing HBsAg tests GS HBsAg EIA 3.0 Ortho HBsAg ELISA Test System 3 Abbott PRISM HBsAg ChLIA 23 January, 2003 23 April, 2003
18 July, 2006 Anti-HBc test Abbott PRISM HBc ChLIA 13 October, 2005 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) 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 Current Incidence and Residual Risk of HBV Infection Two methods for modeling residual risk 1. Based on incidence from newly identified seroconverters (repeat donor data used) 2. 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 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 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) OBrien et al, Transfusion, 2007, 47:316-325 OBrien et al, Transfusion, 2008, 48:2323-2330 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 HBV Prevalence Linauts 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 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 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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