Donated blood sample involved in HIV transmission, even though donation tested for HIV RNA

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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.

Glossary

ribonucleic acid (RNA)

The chemical structure that carries genetic instructions for protein synthesis. Although DNA is the primary genetic material of cells, RNA is the genetic material for some viruses like HIV.

 

plasma

The fluid portion of the blood.

assay

A test used to measure something.

antigen

Something the immune system can recognise as 'foreign' and attack.

p24

An HIV antigen that makes up most of the HIV viral core. High levels of p24 are present in the blood during the short period between HIV infection and seroconversion, before fading away. Since p24 antigen is usually detectable a few days before HIV antibodies, a diagnostic test that can detect p24 has a slightly shorter window period than a test that only detects antibodies.

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

Protection of UK blood supply from HIV, HBV, HCV: infected donations rarely enter supply - news story

References

Delwert EL et al. First report of human immunodeficiency virus transmission via an RNA-screened blood donation. Vox Sanguinis 86: 171-177, 2004.