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FDA Workshop “Data and Data Needs to Advance Risk Assessment for Emerging Infectious Diseases for Blood
and Blood Products” November 29, 2011, Gaithersburg MD
Data Needed and Examples of Application in FDA Risk Assessments of Emerging
Transfusion-Transmitted Diseases
Hong Yang, Ph. D.Office of Biostatistics and Epidemiology,
CBER, FDA
Outlines
• Important data needed for risk assessment (RA) for emerging transfusion-transmitted diseases
• Case study- vCJD RA
• Case study- Malaria RA
RA Model for Transfusion-Transmitted Infectious Diseases
Recipient Risk (Probability infection)
Blood Donation: (Probability infectious)
Donor Risk (Probability infected)
Disease prevalence
Donor questionnaire screening
Infection rate
Data needed for RA of Emerging Transfusion-Transmitted Diseases
• Disease prevalence– Blood testing for antigens (MSM RA)– Clinical case report (Malaria RA)– Biomarker prevalence (vCJD RA)– Donor characteristics-risk factors (vCJD RA)
• Efficiency of donor questionnaire screening– Information from existing deferral (vCJD, Malaria RAs)– Screening errors differ by targeted deferral
• Infection rate– Transfusion Look Back study (T. cruzi RA)– Animal data (vCJD RA)– Assuming 100% infection rate (Malaria RA)
Data for Estimation of Disease Prevalence among Donors (1)
• Blood testing for antigens– Most relevant– Likely unavailable for EID
Application in FDA RA:
Data on HIV and HBV prevalence in
MSM population (MSM RA)
Data for Estimation of Disease Prevalence among Donors (2)
• Clinical case report– Under-estimate prevalence when
incubation period of disease is long
– Information lag for EID
Application in FDA RA: CDC Malaria Surveillances Report (Malaria RA)
Data for Estimation of Disease Prevalence among Donors (3)
• Biomarker prevalence survey– A good surrogate ?
Application in FDA RAs: • UK tissue surveillance study
(vCJD RA) • Seroprevalence data (T. cruzi
RA)
normal brain
vCJD florid plaque
Data for Estimation of Disease Prevalence among Donors (4)
• Donor characteristics-risk factors ─ Travel survey
• Data from travel agency have limitation in scale and mode of transportation
• Donor data more relevant– Behavior survey
Application in FDA RAs:• Travel survey (vCJD and Malaria RAs)• MSM behavior survey (MSM RA)
Data needed for RA of Emerging Transfusion-Transmitted Diseases
• Disease prevalence– Blood testing for antigens (MSM RA)– Clinical case report (Malaria RA)– Biomarker prevalence (vCJD RA)– Donor characteristics-risk factors (vCJD RA)
• Efficiency of donor questionnaire screening– Information from existing deferral (vCJD, Malaria RAs)– Screening errors differ by targeted deferral
• Infection rate– Transfusion Look Back study (T. cruzi RA)– Animal data (vCJD RA)– Assuming 100% infection rate (Malaria RA)
Data needed for RA of Emerging Transfusion-Transmitted Diseases
• Disease prevalence– Blood testing for antigens (MSM RA)– Clinical case report (Malaria RA)– Biomarker prevalence (vCJD RA)– Donor characteristics-risk factors (vCJD RA)
• Efficiency of donor questionnaire screening– Information from existing deferral (vCJD, Malaria RAs)– Screening errors differ by targeted deferral
• Infection rate– Transfusion Look Back study (T. cruzi RA)– Animal data (vCJD RA)– Assuming 100% infection rate (Malaria RA)
Case study 1
vCJD Risk Assessment for Plasma-Derived Blood Clotting Factors
Estimate of Donor Risk
12
Donorprevalence
Donor’s travels to
vCJD regions
Donor questionnaire
screening
UK
France EU Military Bases in EU
vCJD prevalence in epidemic regions
Model Inputs (1)- Prevalence of vCJD in the UK
1. Epidemiological modeling vCJD clinical cases (LOWER estimate) FDA model estimated UK prevalence in 2002: ~4.5 per million
2. Tonsil/appendix tissue surveillance in UK patients (HIGHER estimate) Hilton, et al. 2004
1 in 4,225 individuals, or 237 per million
13
• Donor Travel Survey– Blood Donor Travel Survey 1980-1996 (ARC
2000) • Number donors traveled, destination, year,
duration
• Efficiency of donor deferral– Assumed a mean 92% based on data for other
diseases
14
Model Inputs (2)- Prevalence of vCJD in the US Donors
Case study 2
Malaria Risk Assessment
Estimate of Donor Risk
16
Number donors who traveled
Donor questionnaire
screening
Donor prevalence
Case incidence among travelers
Infection prevalence among travelers
Input Data - Donor Risk for Malaria
• Annual number donor who travels to Malaria endemic areas (ARC 2007, personal communication)– Nationwide deferrals projected based on data collected
in 6 blood centers
• Malaria incidence report (CDC 2001-2005)– Imported/acquired in US, US travelers/immigrants,
regions of exposure, Plasmodium spp.
• Probability asymptomatic malaria (CDC 2001-2005)– <10% cases not showing symptoms after 90 days since
exposure
Summary
• The most important data needed: disease prevalence, efficiency of donor questionnaire screening and infection rate
• Data contributed by blood centers and other stake holders has been essential for FDA RA
• We need more and better data
Acknowledgements
• FDA workshop working group– Anderson, Steven– Forshee, Richard– Gallagher, Lou– Walderhaug, Mark