A Transfusion Medicine Specialist in New Zealand reports that their Blood Collection Service classifies donors as being either high or low risk for HIV or HCV infection according to the combination of test results for anti-HIV and anti-HCV (by ELISA) coupled with indeterminate HIV Western Blot confirmation or HCV-RIBA results, respectively. High risk and low risk individuals are treated differently. For example if a donor has a positive anti-HCV (ELISA) test and is also positive for antibodies to c22 or NS3 on HCV-RIBA, they follow that donor more closely than if the donor has antibodies to NS4 or NS5. During 2002 they introduced mini-pool testing for HIV RNA and HCV RNA for all of their collected blood. In addition, donations testing positive for anti-HIV or anti-HCV by ELISA (irrespective of their HIV-Western Blot or HCV-RIBA result) are also individually tested for HIV-RNA or HCV-RNA. The New Zealander would like to know how others deal with donors who demonstrate various combinations of positive (reactive) test results for HIV and HCV.

ADDENDA July 29, 2005

1. Editor's Note: The following e-Network Forum discussions:

• Notification of donors who test HIV and/or HCV ELISA positive but confirmatory testing is indeterminate or negative
• Use of nucleic acid amplification testing (NAT) results in notification of blood donors to resolve uncertain results for HIV and HCV
• Re-entry of donors who tested positive in an HCV ELISA antibody screen but RIBA-negative, prior to implementation of HCV-RNA testing

and ...

Exceptions and Alternative Procedures Approved Under 21 CFR 640.120: As of July 26, 2005. (Excerpt from item #11)

21 CFR 610.40(e), 610.46(b) & 630.6(a):

1. Discontinue supplemental testing for HIV-1 and HCV for each donation with a repeatedly reactive anti-HIV and anti-HCV EIA screening test only if the individual donation HIV-1 and HCV NAT is reactive or discriminatory reactive using HIV-1 and HCV primers. The supplemental testing for HIV-1 and HCV must still be performed on all donations with a repeatedly reactive anti-HIV and anti-HCV EIA screening test and a HIV-1 and HCV NAT that is non-reactive or discriminatory non-reactive. Also exempt from obtaining HIV-1 and HCV supplemental test results prior to donor notification for these donors. Donors must still be notified of their deferral and the reason for the deferral, including the HIV-1 and HCV NAT results. In addition, exempt from notifying consignees of the results of the HIV-1 supplemental testing. Consignees must still be notified of the results of the repeatedly reactive anti-HIV EIA screening test and reactive or discriminatory reactive HIV-1 NAT results within 30 calendar days after the repeatedly reactive anti-HIV EIA results.
2. Discontinue supplemental testing for HIV-1 for each donation with a repeatedly reactive anti-HIV EIA screening test only if the individual donation HIV-1 NAT is reactive or discriminatory reactive using HIV-1 primers. The supplemental testing for HIV-1 must still be performed on all donations with a repeatedly reactive anti-HIV EIA screening test and a HIV-1 NAT that is non-reactive or discriminatory non-reactive. Also exempt from obtaining HIV-1 supplemental test results prior to donor notification for these donors. Donors must still be notified of their deferral and the reason for the deferral, including the HIV-1 NAT results. In addition, exempt from notifying consignees of the results of the HIV-1 supplemental testing. Consignees must still be notified of the results of the repeatedly reactive anti-HIV EIA screening test and reactive or discriminatory reactive HIV-1 NAT results within 30 calendar days after the repeatedly reactive anti-HIV EIA results.

may be germane to the current issue.

ADDENDA July 31, 2005

2. A colleague who works for a multi-state network of blood collection centers in the USA reports that at present time, within the confines of routine operations, and outside of a specific investigational study protocol, they follow the package inserts with a few exceptions. If a donor is HCV EIA repeat reactive (RR), RIBA positive but RNA negative, they know that there are three possible explanations: false pos RIBA, resolved HCV infection or an HCV viral load less than the cutoff of minipool or even individual donor (ID) NAT. They have retested minipool neg samples and about 2-5% will repeat by ID NAT (RIBA pos); they no longer do this routinely. For HIV EIA RR, WB positive but RNA negative samples, they do retest the index sample by ID NAT (PCR; alternate NAT) and follow the donor. This is because about 1/2 of such cases are due to false positive western blots (these can be easily sorted from true positives also by low EIA S/CO and weak banding on western blot, typically lacking a band at p31). For NAT reactive samples that are Ab nonreactive (HIV or HCV), they also investigate these donors by retesting the index sample by single unit NAT (TMA and PCR) and retesting serology; these donors are also enrolled into follow up until seroconversion occurs.

ADDENDA Aug. 3, 2005

3. Dr. Leslie H. Tobler, Senior Scientist for Blood Systems Research Institute (attribution used with permission) reports that in her opinion, what the New Zealand blood bank is doing makes a lot of sense, because using HCV RIBA indeterminate band patterns it may be possible to distinguish individuals who have a probability of evolving into RIBA positive band patterns from those that will not. However, the issue with HIV-1 Western blots is not as straight forward. Dr. Tobler reports that the following information has been submitted to the 2005 Annual AABB meeting and has been accepted as a poster. Briefly, they have established a study group consisting of 1) Minipool negative RIBA confirmed positive blood donors and 2) Minipool positive RIBA confirmed blood donors. When 85 minipool-NAT negative donations were tested in duplicate by individual transcription mediated amplification, 6 (7%) tested RNA positive, indicating low-level viremia. To date, 59 HCV minipool NAT negative donors who where TMA negative (duplicate testing) on index have been recalled and retested in duplicate using individual transcription mediated amplification. 52 (88%) of 59 cases remained HCV RNA-negative on follow-up, whereas 7 (12%) were either RNA-positive in both (4 cases) or in one of two TMA tests (3 cases). These observations indicate that among minipool-NAT negative donations there exists a subpopulation of individuals with very low and fluctuating viremia. Thus, the approach the New Zealand blood banker is using should identify these donors in the process of resolving their infection, i.e. they have become RIBA indeterminate.

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator