Researchers have developed a blood test that could revolutionize monitoring for heart transplant rejection, potentially eliminating up to 80% of the invasive tissue biopsies currently required to detect this life-threatening condition. The test performed better than traditional biopsies in a study of nearly 200 heart transplant recipients, detecting problems even when no outward signs of rejection were evident.
The study, primarily funded by the National Heart, Lung, and Blood Institute (NHLBI) and published in Circulation, represents a significant advance in transplant medicine. "There's an urgent need for an alternative method to monitor patients for acute heart transplant rejection," said Sean Agbor-Enoh, M.D., Ph.D., study co-author and chief of the NHLBI's Laboratory of Applied Precision Omics.
Revolutionary Detection Method
The donor-derived cell-free DNA test tracks DNA markers from the organ donor that appear in the blood of the transplant recipient. When cells from the donor organ are injured or dying, they release more donor DNA fragments into the bloodstream compared to healthy cells. Higher amounts of donor DNA therefore indicate a higher risk for transplant rejection.
"We showed in our initial assessment that this 'liquid biopsy' is highly sensitive for detecting acute rejection, finding it weeks to months before current clinical tools," said Hannah Valantine, M.D., senior study author and former lead investigator of the Laboratory of Organ Transplant Genomics at NHLBI.
Superior Performance in Clinical Testing
The research team collected blood samples from 171 people who had recently undergone heart transplantation at five regional transplant centers within or near the Washington, D.C.-metropolitan area. The sampling included nearly 2,000 cell-free DNA measurements over an 18-month monitoring period. The study population included a high percentage (about 44%) of African Americans.
The blood test demonstrated superior performance compared to tissue biopsy, detecting higher amounts of rejection markers and earlier signs of rejection. Notably, it detected more instances of other types of transplant injury missed by biopsy, including antibody-mediated rejection, one of the deadliest forms of rejection and the hardest to treat and diagnose.
The test may be able to detect rejection as early as 28 days after heart transplantation and at least three months before rejection is detectable using heart tissue biopsy. This early detection capability is crucial, as acute rejection typically occurs in the first three to six months after transplantation.
Addressing Current Limitations
Current monitoring methods rely on frequent and painful biopsies of heart tissue, which carry risks of damaging the heart and are limited by their invasiveness and reliability. These biopsies must be performed in hospitals, whereas specimens for the new blood test can be collected at almost any commercial blood-collecting center.
"This test will not completely eliminate the need for invasive procedures, but it can eliminate about 80% of the biopsies currently performed after heart transplant," said study co-author Palak Shah, M.D., a heart disease specialist at Inova Heart and Vascular Institute.
Potential for Reducing Health Disparities
The test holds particular promise for addressing serious health disparities in transplant outcomes. Because African Americans tend to have higher rates of heart transplant rejection and experience poorer transplant outcomes than other groups nationwide, the test could help reduce existing transplant-related health disparities that have persisted for decades.
Researchers are using the blood test to further study the mechanisms underlying acute rejection and explore why African Americans tend to have higher rates of transplant rejection, with the goal of eliminating this health disparity.
Additional Benefits and Future Prospects
Beyond its diagnostic capabilities, the noninvasive blood test may provide significant financial savings and offer a potentially safer alternative to invasive biopsies during viral outbreaks like the current COVID-19 pandemic. The test could be particularly valuable given the critical shortage of donor organs.
However, researchers acknowledge that additional clinical studies, including randomized controlled trials, are needed to confirm these findings before the test can become a routine monitoring tool. The exact timeline for clinical availability remains unclear.
"This could potentially save lives in the wake of a critical shortage of donor organs," Valantine noted, emphasizing the broader implications of this breakthrough for transplant medicine.
