A case of HIV transmission in the US involving a blood donation that had been screened for HIV RNA is reported in the March edition of Vox Sanguinis.
The case involved an individual who had been very recently infected with HIV, but had not yet serocoverted and had a very low viral load. It is the first reported instance of HIV being transmitted by donated blood that had been screened using minipool nucleic acid amplification testing (MR-NAT), which was introduced into the US in 1999 (minipooling involves the pooling of sera from 16-24 blood donors in order to speed up the process of HV RNA testing while holding down the cost of screening; other countries may use larger pools).
However, investigators are stressing that efforts to protect the blood supply from donations infected with HIV and other infectious diseases such as hepatitis C virus (HCV) are very effective, and are likely to become even more so when the enhanced individualised donation NAT (ID-NAT) assays become more widely used, even though this is likely to have considerable cost implications.
In August 2000, a 32-year-old man, who denied any high-risk HIV behaviour, donated blood. This donation tested negative for HIV antibodies, p24 antigen and HIV and HCV RNA using an NAT assay on a pool of 24 donations. The donated blood was then released for transfusion.
In December 2000, the same man donated blood again. This time it tested positive for HIV RNA using the MP-NAT assay, but was negative for p24 antigen or other viral markers. The man again denied any HIV risk behaviours.
Investigators established that the blood donated in August had been used in a blood transfusion in February 2001. The recipient was notified, asked if they were in a group at high risk of HIV, and offered an HIV antibody and viral load test. The individual tested HIV-positive with a viral load of 32,000 copies/ml and started HAART.
The frozen plasma from the infected donation and blood from the recipient were tested to see if the HIV had a genetic linkage. Seven independent tests were conducted and revealed that the HIV in both samples had closely related genetic sequences and was consistent with “HIV transmission as a result of… transfusion from the implicated donor.”
In order to determine the ability of MP-NAT assays to detect potentially infectious donations, plasma from the infected donation was retested using three different assays. Inconsistent results emerged, with two assays providing negative results. However, the third assay revealed a low-level viral load, below 150 copies/ml. When the investigators retested the plasma using individualised NAT (ID-NAT), these assays, which individually test each donation for infectious agents, produced positive results.
The investigators comment, "these results demonstrate that very low-level viraemia during the preseroconversion window period is infectious by blood transfusion, and confirms that… a very small risk of transfusion-associated HIV transmission remains, even after screening with MP-NAT."
However, the investigators emphasise that it is important to place this case in context. During the period that MP-NAT has been in use in the US, over 35 million donated blood units have been tested and used in transfusions in 20 million patients. This case was the first HIV infection noted involving screened blood (although two additional HIV-infected donations resulting in onward transmission and an HCV-infected donation have subsequently been identified). A case of HIV transmission despite MP-NAT has been detected in France. The use of ID-NAT is, say the investigators, likely to reduce this incidence even further, but will have resource and cost implications.
Further information on this website
Delwert EL et al. First report of human immunodeficiency virus transmission via an RNA-screened blood donation. Vox Sanguinis 86: 171-177, 2004.