Guidance for Industry 
 
Requalification Method for Reentry of 

Blood Donors Deferred Because of Reactive 

Test Results for Antibody to Hepatitis B 

Core Antigen (Anti-HBc) 

 
 
 
 
 
 
 
 
 
 
 
Additional copies of this guidance are available from the Office of Communication, Outreach 
and Development (OCOD) (HFM-40), 1401 Rockville Pike, Suite 200N, Rockville, MD 20852
1448, or by calling 1-800-835-4709 or 301-827-1800, or email ocod@fda.hhs.gov, or from the 
Internet at  
http://www.fda.gov/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guida 
nces/default.htm. 
 
For questions on the content of this guidance, contact OCOD at the phone numbers listed above. 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Biologics Evaluation and Research 
May 2010
  Contains Nonbinding Recommendations 
 
 
 
 
 
 
Table of Contents 
 
 
I.   INTRODUCTION....................................................................................................... 1 
 
II.   BACKGROUND ......................................................................................................... 2 
 
III.   RECOMMENDATIONS............................................................................................ 5 
 
IV.   IMPLEMENTATION ................................................................................................ 6
  
V.   REFERENCES............................................................................................................ 7 
 
APPENDIX.............................................................................................................................. 9
  
i  Contains Nonbinding Recommendations 
 
 
Guidance for Industry 
 
Requalification Method for Reentry of Blood Donors Deferred Because 
of Reactive Test Results for Antibody to Hepatitis B Core Antigen 
(Anti-HBc) 
 
 
This guidance represents the Food and Drug Administrations (FDAs) current thinking on this 
topic. It does not create or confer any rights for or on any person and does not operate to bind 
FDA or the public. You can use an alternative approach if the approach satisfies the 
requirements of the applicable statutes and regulations.  If you want to discuss an alternative 
approach, contact the appropriate FDA staff. If you cannot identify the appropriate FDA staff, 
call the appropriate number listed on the title page of this guidance. 
 
 
I. INTRODUCTION 
 
We, FDA, are issuing this guidance to provide you, establishments that collect Whole Blood or 
blood components intended for transfusion, with recommendations for a requalification method 
or process for the reentry of deferred donors into the donor pool based on a determination that 
previous tests that were repeatedly reactive for antibodies to hepatitis B core antigen (anti-HBc) 
were falsely positive and that there is no evidence of infection with hepatitis B virus (HBV).  
Currently, donors who are repeatedly reactive on  more than one occasion for anti-HBc (samples 
from more than one collection from the same donor are repeatedly reactive for anti-HBc) must 
be indefinitely deferred in accordance with Title 21 Code of Federal Regulations, section 
610.41(a) (21 CFR 610.41(a)). Although it may seem  unlikely that two anti-HBc tests would be 
falsely positive, such situations have occurred with some frequency because of the relative non-
specificity of these tests. The result is that many otherwise suitable donors are indefinitely 
deferred because of their anti-HBc test results, even though medical follow-up of such donors 
indicates that they are not infected with HBV.   
 
The availability of FDA-licensed hepatitis B virus nucleic acid tests (HBV NAT), which are 
particularly sensitive when single samples are tested, provides an additional, powerful method of 
determining whether a donor who has been deferred because of anti-HBc reactivity is truly 
infected with HBV.  Due to the availability of FDA-licensed HBV NAT and the improved 
specificity of anti-HBc assays, we are recommending in this guidance a reentry algorithm  for 
donors deferred due to falsely positive repeatedly reactive tests for anti-HBc.  This guidance 
finalizes the draft guidance of the same title dated May 2008. 
 
FDAs guidance documents, including this guidance, do not establish legally enforceable 
responsibilities. Instead, guidances describe the FDAs current thinking on a topic and should be 
viewed only as recommendations, unless specific regulatory or statutory requirements are cited.  
The use of the word should in FDAs guidances means that something is suggested or 
recommended, but not required. 
1 
 Contains Nonbinding Recommendations 
 
 
 
 
 
II. BACKGROUND  

 
A.   Clinical Significance of Donor Screening for Hepatitis B Virus Infection 
 
HBV is an enveloped virus with a partially duplex circular deoxyribonucleic acid (DNA) 
genome of approximately 3,200 bases.  It is a major human pathogen that causes acute 
and chronic hepatitis, cirrhosis and hepatocellular carcinoma (Ref. 1).  The mortality of  
acute HBV infection is about 1%. Most primary infections in adults are self-limited.  The 
virus is cleared from the blood and liver, and individuals develop a lasting immunity.  
However, 2% to 6% of persons above the age of 5 years, and 30% to 90% of infected  
children under the age of 5 years (Ref. 2) develop chronic infections that generally are 
asymptomatic (i.e., a carrier state), but may not be benign.  About 20% of chronically 
infected individuals develop cirrhosis, and chronically infected subjects have 100 times 
higher risk of developing hepatocellular carcinoma than non-carriers.  In the United 
States, deaths from chronic HBV infection are estimated to range from 3,000 to 5,000 
individuals per year (Ref. 2). 
 
Currently, HBV is transmitted by blood transfusions more frequently than hepatitis C  
virus or human immunodeficiency virus.  The residual risk of post-transfusion HBV 
infection from donations screened for hepatitis B surface antigen (HBsAg) and anti-HBc 
has been estimated as 1 in 205,000 (Ref. 3) to 1 in 269,000 (Ref. 4) per donated unit.  The 
major cause of HBV transmission by blood is attributable to donations from 
asymptomatic donors with acute HBV infections who have not yet developed HBsAg or 
anti-HBc (i.e., donors in the seronegative window period) and, in some cases, from  
donors with chronic infections in which serological markers are not detected (occult 
hepatitis B). Seronegative blood donations from infected individuals can transmit 
hepatitis B. In such cases, lookback studies using polymerase chain reaction have shown 
that HBV DNA can be detected at low levels in the donors blood (Ref. 5).   
 
HBsAg becomes detectable in blood 30 to 60 days after infection followed by the 
emergence of anti-HBc.  Viremia develops several weeks before HBsAg is detected, and 
can reach 109-1010 virions/ml in acute infections (Ref. 1).  Upon clearance of the HBV 
infection by the immune response, the HBsAg disappears from the blood of individuals, 
while detectable anti-HBc and antibody to hepatitis B surface antigen (anti-HBs) usually 
persist indefinitely. However, there is evidence that anti-HBc can decrease and even 
disappear over a period of decades in resolved infections (Ref. 6).  Nonetheless, in 
chronically infected individuals, tests for HBsAg and anti-HBc usually remain positive 
for life and lower viral titers can be detected in blood for a long period although they tend 
to decline over time.  
 
HBV NAT assays for detection of HBV DNA have been developed, and have been 
licensed for screening blood donations using a minipool sample format.  These assays are 
also indicated for testing samples from individual donations, thus increasing test 
2 
 Contains Nonbinding Recommendations 
 
 
 
sensitivity. In a meeting of the Blood Products Advisory Committee (Committee or 
BPAC) on October 21, 2004 (Ref. 7), we requested scientific comment on a reentry 
algorithm for donors deferred for repeatedly reactive anti-HBc test results on more than 
one occasion.  The algorithm was based on follow-up testing of the donor for HBsAg, 
anti-HBc, and HBV DNA by sensitive HBV NAT.  Under this plan, HBV DNA testing 
using an FDA-licensed NAT would replace a previously considered recommendation for 
donor reentry that included antibody to hepatitis B surface antigen (anti-HBs) testing.   
We no longer propose additional testing for anti-HBs as part of donor reentry because 
extensive hepatitis B vaccination programs have been in place for a number of years, 
resulting in many individuals having anti-HBs from vaccination.  As a result, anti-HBs 
now has questionable value as a marker of hepatitis B infection. While the Committee did 
not take a formal vote on the algorithm, the Committee discussed this approach and did 
not express concerns about the adequacy of this plan as a reentry algorithm.   
 
Since the 2004 BPAC meeting referred to above, we have licensed qualitative tests for 
the direct detection of HBV DNA in human plasma from donors, including donors of 
Whole Blood and blood components, Source Plasma and other living donors, that have 
sensitivities of <2 International Units (IU)/mL (about 10 copies HBV DNA/mL) at 95% 
detection for HBV DNA when specific procedures are used.1 The availability of 
sensitive, FDA-licensed, HBV NAT assays provides an additional, powerful method of 
determining whether a donor, who has been deferred because of anti-HBc reactivity, is 
truly infected by HBV.  Due to the availability of FDA-licensed HBV NAT assays and 
the improved specificity of anti-HBc assays, we are recommending a reentry algorithm 
for anti-HBc in this guidance. Empirical studies support utility of this algorithm (Ref. 8).   
 
B.   Rationale and Procedure for the Requalification Method for Reentry  
 
Under 21 CFR 610.40(a), you must test each donation of human blood or blood 
component intended for use in preparing a product, including donations intended as a 
component of, or used to prepare, a medical device, for evidence of infection due to 
HBV, among other communicable disease agents.  Testing for evidence of infection of 
HBV includes testing for the presence of HBsAg and anti-HBc.  In addition, some blood 
establishments also test blood donations for HBV DNA by HBV NAT. 
 
Under 21 CFR 610.41(a), as a general matter, you must defer donors who test reactive2  
with respect to the battery of screening tests required under 21 CFR 610.40.  However, 
donors who test repeatedly reactive for anti-HBc on only one occasion do not need to be 
                                                 
1 COBAS AmpliScreen HBV Test (Roche Molecular Systems, Inc., Pleasanton, California): Triplicate testing  using 
 
the multiprep specimen processing procedure.   

Procleix  ULTRIO  Assay (Gen-Probe, Inc., San Diego, California):   Testing 6 replicates. 
  
2 In  21 CFR  610.41(a), FDA requires that  blood establishments  defer donors who test reactive by a screening test for 

evidence of infection due to a communicable disease agent(s) listed in section 610.40(a).  In section 610.41(a)(1),  

however, a donor who tests reactive for anti-HBc on only one occasion is not required to  be deferred.  In this 

guidance, we refer to  reactive test results for HBsAg and anti-HBc as repeatedly reactive to accurately describe 

the testing algorithms for HBsAg and anti-HBc. 

 
3 
 Contains Nonbinding Recommendations 
 
 
 
deferred (21 CFR 610.41(a)(1)).  Donations collected from these donors are not suitable 
for allogeneic transfusions (21 CFR 610.40(h)(1) and (2)) (Ref. 9), but such donations, if 
otherwise nonreactive when tested for communicable disease agents as required under 21 
CFR 610.40, may be used for further manufacturing into plasma derivatives without FDA 
prior approval. (21 CFR 610.40 (h)(2)(v). Donors who test reactive on more than one 
occasion do not fall within this exception and must be deferred (21 CFR 610.41(a)).  
 
Under 21 CFR 610.41(b), a deferred donor subsequently may be found to be suitable as 
a donor of blood or blood components by a requalification method or process found 
acceptable for such purposes by FDA. 3    
 
Until now, we have not recommended a requalification method for reentry of donors 
deferred due to repeatedly reactive test results for anti-HBc because there was no 
supplemental (additional, more specific) test available.  Although donor screening for 
anti-HBc has contributed to blood safety, a large proportion of donors with anti-HBc 
reactivity who fulfill all other donor suitability criteria have been indefinitely deferred on 
the basis of potentially false positive anti-HBc test results (Refs. 10, 11).  It is estimated 
that as many as 21,500 potentially eligible donors were deferred annually in the late 
1980s and 1990s because of false positive anti-HBc results, and that over 200,000 donors 
could be eligible for reentry (Ref. 10). 
 
For purposes of reentering into the donor pool, a donor who has been indefinitely 
deferred because of having tested repeatedly reactive for anti-HBc on more than one 
occasion, we recommend in Section III of this guidance that, after a minimum of 8 weeks 
following the last repeatedly reactive anti-HBc test, you obtain from the donor a new, 
pre-donation blood sample (i.e., a blood sample that is obtained before the next donation) 
for follow-up testing, using FDA-licensed tests for HBsAg, anti-HBc and HBV DNA by 
NAT. If the new, pre-donation blood sample test results are negative for HBsAg, anti-
HBc and HBV DNA, the donor may return to donate blood.  When the donor returns to 
donate, after the tests for HBsAg, anti-HBc, and HBV DNA on the pre-donation sample 
have been determined to be negative, we recommend that you reenter the donor as 
eligible to donate Whole Blood and blood components, provided that the donor meets all 
eligibility criteria. Note that the reentry of a donor permits prospective donations from a 
reentered donor who meets donor suitability criteria.  It does not affect the status of 
previous collections from that donor. 
 
For donor retesting, we recommend that a minimum 8-week (56 days) period elapse 
following the last repeatedly reactive anti-HBc test, because this time period provides 
sufficient confidence that at least one of the three HBV markers (HBsAg, anti-HBc, and 
HBV DNA) will be detectable if the donor had been truly infected with HBV at the time  
of the last anti-HBc reactive donation (Ref. 1).  In addition, eight weeks is the minimum  
time period permitted between donations of Whole Blood, with limited exceptions (21  
                                                 
3  A deferred  donor may serve as an autologous  donor in accordance with  21 CFR 610.40  and 21 CFR 610.41.  Note 
that a deferred  donor that donates for autologous  use is not  deemed  to be reentered and remains deferred, until the 
criteria for reentry are met. 
4 
 Contains Nonbinding Recommendations 
 
 
 
CFR 640.3(b)). 
 
For purposes of reentry, we recommend that you use an FDA-licensed HBV NAT labeled 
as having a sensitivity of < 2 IU/mL at 95% detection rate [1 IU = ~5 copies].  Donors 
with negative results for HBV DNA at this level of sensitivity are highly unlikely to be  
infected with HBV (Ref. 12).  Depending upon the assay and the platform used, this 
sensitivity may only be achieved when testing individual donor samples.    
 
 
III. RECOMMENDATIONS 
 
A.   You may reenter into the donor pool, a donor who has been indefinitely deferred 
solely because of repeatedly reactive tests for anti-HBc on more than one occasion 
if (see flow chart in the Appendix): 
 
1. 	  After a minimum of 8 weeks following the last repeatedly reactive anti-HBc 
test, you collect a follow-up sample from the donor, and this sample tests 
negative on FDA-licensed tests for HBsAg, anti-HBc, and HBV DNA by NAT 
(sensitivity at 95% detection rate of <2 IU /mL)   
 
    and 
 
2. 	  When the donor presents to donate, after the new, pre-donation blood sample 
tests negative on FDA-licensed tests for HBsAg, anti-HBc, and HBV DNA by 
NAT, you determine that the donor meets all eligibility criteria for donors of 
Whole Blood and blood components. 
 
B.   You should continue to indefinitely defer a donor who was deferred for anti-HBc 
reactivity on more than one occasion and whose sample or donation tests: 1) 
repeatedly reactive on the HBsAg test (whether or not the neutralization test is 
positive); 2) repeatedly reactive on the anti-HBc test; or 3) reactive on the HBV 
NAT. Positive results on tests for HBsAg, anti-HBc or HBV DNA by NAT may be 
useful in donor counseling. 
 
C.   If you wish to perform follow-up testing on a donor who is deferred because of anti-
HBc test results, you may do so before the end of the 8-week waiting period for 
donor notification purposes or for medical reasons.  Negative test results on follow-
up for HBsAg, anti-HBc, and HBV DNA by NAT (sensitivity at 95% detection rate 
of < 2 IU/mL), may be useful in donor counseling.  However, only negative results 
for all three tests (HBsAg, anti-HBc, and HBV NAT), obtained at least 8 weeks 
after the last repeatedly reactive anti-HBc result, would qualify the donor for 
reentry. If you obtain a reactive HBV NAT, or repeatedly reactive HBsAg or anti-
HBc, or positive HBsAg result on any of these tests during this 8-week waiting 
period, the donor would not be eligible for reentry, and we recommend that you 
defer the donor indefinitely. 
5 
 Contains Nonbinding Recommendations 
 
 
 
 
A donor who has been requalified as described above in Section III. A. 1 and 2 may on 
subsequent occasions be indefinitely deferred solely because of repeatedly reactive tests for anti-
HBc on more than one occasion.  You may reenter such a donor into the donor pool by again 
following all procedures described in Section III. A.      
 
    
IV. IMPLEMENTATION 
 
We consider the recommendations in this guidance to be an acceptable requalification method 
for reentry of donors deferred due to falsely positive repeatedly reactive tests for anti-HBc.  
Licensed establishments implementing these recommendations must report this change to FDA 
as required under 21 CFR 601.12(a). We consider implementation of recommendations in this 
guidance in their entirety and without modification to be a minor change to an approved license 
application. Therefore, licensed establishments are not required to have FDA prior approval and 
may submit a statement of this change in an annual report under 21 CFR 601.12(d), indicating 
the date that the revised standard operating procedures were implemented.  Unlicensed 
establishments implementing recommendations in this guidance in their entirety and without 
modification are not required to report this change. 
 
We do not consider implementation of an alternative requalification method from that described 
in this guidance to be acceptable, unless approved by FDA for such purpose.  In accordance with 
21 CFR 610.41(b), you must not reenter a donor unless the requalification method or process is 
found acceptable for such purposes by FDA.  Licensed establishments intending to use an 
alternative requalification method must submit a supplement for prior approval, as required 
under 21 CFR 601.12(b). Similarly, under 21 CFR 610.41(b), FDA must find an alternative 
requalification method proposed by an unlicensed establishment to be acceptable before it is 
implemented. 
 
 
 
6 
 Contains Nonbinding Recommendations 
 
 
 
 
V. REFE RENCES 
 
 
1. 	  Ganem, D., Prince, A.M., Hepatitis B Virus Infection  Natural History and Clinical 
Consequences. New England Journal of Medicine, 350, 1118-1129 (2004). 
 
2. 	  Alter, M.J., Centers for Disease Control and Prevention.  Epidemiology of HBV Infection 
and Prevention Programs.  Presentation to the Advisory Committee on Blood Safety and 
Availability, August 27, 2004. 
http://www.hhs.gov/ophs/bloodsafety/advisorycommittee/pastmeetings/pastmeetings.html#o  
 
3. 	  Dodd, R., et al., Current Prevalence and Incidence of Infectious Disease Markers and  
Estimated Window-Period Risk in the American Red Cross Blood Donor Population. 
Transfusion, 42, 975-979 (2002). 
 
4. 	  Busch, M.P., Transfusion-Transmitted Viral Infections: Building Bridges to Transfusion 
Medicine to Reduce Risks and Understand Epidemiology and Pathogenesis. Transfusion, 
46, 1624-1640 (2006). 
 
5.	   Roth, W.K., Weber, M., Petersen, D., Drosten, C., Buhr, S., Sireis, W., Weichert, W., 
Hedges,D., Seifried, E., NAT for HBV and Anti-HBc Testing Increase Blood Safety.  
Transfusion, 42, 869-875 (2002). 
 
6. 	  Seeff, L.B., Beebe, G.W., Hoofnagle, J.H., et al., A Serologic Follow-Up of The 1942 
Epidemic of Post-Vaccination Hepatitis in the United States Army.  New England Journal 
of Medicine, 316(16), 965-970 (1987). 
 
7. 	  FDAs Current Thinking on Reentry of Donors Deferred for Repeated Detection of Antibody 
to Hepatitis B Core Antigen: Blood Products Advisory Committee 81st meeting; Transcript, 
October 21, 2004. ww.fda.gov/ohrms/dockets/ac/cber04.html#BloodProducts.  
 
8.	   Katz, L., Strong, D.M., Tegtmeier, G., Stramer, S., Performance of an Algorithm for 
Reentry of Volunteer Blood Donors Deferred Due to False-Positive Test Results for 
Antibody to Hepatitis B Core Antigen.  Transfusion, 48, 2315-2322 (2008). 
 
9. 	  FDA Memorandum to All Registered Blood Establishments:  FDA Recommendations 
Concerning Testing for Antibody to Hepatitis B Core Antigen (Anti-HBc), September 10, 
1991. http://www.fda.gov/cber/memo.htm.    
 
10.  Kleinman, S.H., Kuhns, M.C., Todd, D.S., Glynn, S.A. McNamara, A., DiMarco, A., Busch, 
M.P., For the Retrovirus Epidemiology Donor Study. Frequency of HBV DNA Detection in 
US Blood Donors Testing Positive for the Presence of Anti-HBc:  Implications for 
Transfusion Transmission and Donor Screening.  Transfusion, 43, 696-704 (2003). 
 
7 
 Contains Nonbinding Recommendations 
 
 
 
11.  Tegtmeier, G., Henderson, S., McNamara, A., Kuhns, M., Contribution of Anti-HBc  
Screening to Blood Safety at a Regional Blood Center in the United States.  Transfusion, 37, 
110S (Abstr. S439) (1997). 
 
12.  Reesink, H.W., et al.  	Occult Hepatitis B Infection in Blood Donors.  Vox Sanguinis, 94, 
153-166 (2008). 
8 
 Contains Nonbinding Recommendations 
 
 
 
 
APPENDIX 
 
 
REQUALIFICATION PROCESS FOR DONORS DEFERRED BECAUSE OF  
REPEATEDLY REACTIVE TEST RESULTS FOR ANTI-HBc 
 
 
Donors previously deferred solely because of repeatedly reactive (RR) anti-HBc test on more 
than one occasion 
 
 
 
After a minimum of 8 weeks1 following the last repeatedly reactive anti-HBc test result, test a 
follow-up sample using FDA-licensed HBsAg and anti-HBc tests, and HBV NAT2   
 
 
 
 
 
 
 
HBsAg RR3 or Anti-HBc RR or HBV NAT Reactive   All tests negative 
 
 
 
 
 
  Defer donor indefinitely        Reenter donor 
  (Donor eligible for future donations, 
provided donor meets eligibility criteria)  
 
1 If, for donor notification purposes or for medical reasons, you wish to perform follow-up 
testing on a donor who is deferred because of repeatedly reactive anti-HBc test results before the 
end of the 8-week waiting period and the blood sample tests HBsAg RR or anti-HBc RR or HBV 
NAT reactive, the donor should be indefinitely deferred.  If, however, the sample tests negative 
on all three of these tests, the donor should be retested after a minimum of 8 weeks following the 
last repeatedly reactive anti-HBc test result using licensed HBsAg and anti-HBc tests, and HBV 
NAT. If, at that time, the sample tests negative on all three of these tests (HBsAg, anti-HBc, and 
HBV NAT), the donor may be eligible to donate. 
2 The sensitivity of the HBV NAT used should be < 2 IU/mL, at 95% detection rate. 
3 Regardless of the neutralization test result. 
9