Saturday, September 25, 2010

Blood test to detect organ transplant rejection

By Zara Qadir NewScientist

A simple blood test could help doctors detect telltale signs of transplant rejection. The finding may provide a non-invasive alternative for diagnosing organ rejection before damage occurs.

The technique could help the 40 per cent of heart transplant recipients who experience an acute episode of rejection in their first year after transplantation.

Normally, if organ function drops, a small piece of tissue will be removed and checked for rejection. The trouble is that the organ may already be damaged by the time doctors spot a problem.

A simple blood test for the proteins involved in the inflammatory response of rejection could provide the answer, says Adul Butte at Stanford University School of Medicine in California.

To identify the protein markers involved in organ rejection, Butt and his team used a publically available repository that documented changes in mRNA levels – the molecules that instructs cells to make proteins – during organ rejection. These changes gave the team clues about which proteins appear in the blood during rejection.

From 45 protein candidates, the team zeroed in on 10 that could be identified by tests already used in a clinical setting. Using blood samples from 39 kidney and 63 heart transplant patients they found three proteins which reliably increased during an acute rejection.

Minnie Sarval, who co-authors the study, believes the test could be used to adjust the levels of immunosuppressant drugs administered – increasing them only if rejection is imminent – thus minimizing side-effects. "It could also potentially prompt doctors to conduct a biopsy [only] if necessary rather than biopsying straight away," she says.

More research will show whether these diagnostic markers can predict an acute episode of rejection before any change in organ function.

"Identifying a protein marker that is elevated in the blood before rejection damage could represent a significant advance which could enable early intervention with treatment," says Steven Sacks at the centre for transplantation at King's College London. "Their next challenge would be to examine whether patients treated on the basis of this test do better than those who do not have the benefit of such testing and who have to wait until organ damage occurs before immunosuppressant treatment is increased."

The team are now planning clinical trials and hope their test will be available within three to five years.

Journal reference:PLOS Computational biology, DOI: 10.1371/journal.pcbi.1000940

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