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Heart Transplant Monitoring Test Validated

By LabMedica International staff writers
Posted on 06 Feb 2020
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Image: The myTAIHEART test is a powerful non-invasive test that uses a small sample of blood to determine if a patient is at a low or increased risk of rejecting their heart transplant. myTAIHEART works by measuring the fraction of cell-free DNA (cfDNA) present in the bloodstream that is attributable to the transplanted heart. An elevated donor fraction (DF%) is associated with an increased risk of acute cellular rejection (Photo courtesy of TAI Diagnostics).
Image: The myTAIHEART test is a powerful non-invasive test that uses a small sample of blood to determine if a patient is at a low or increased risk of rejecting their heart transplant. myTAIHEART works by measuring the fraction of cell-free DNA (cfDNA) present in the bloodstream that is attributable to the transplanted heart. An elevated donor fraction (DF%) is associated with an increased risk of acute cellular rejection (Photo courtesy of TAI Diagnostics).
A heart transplant, or a cardiac transplant, is a surgical transplant procedure performed on patients with end-stage heart failure or severe coronary artery disease. Noninvasive risk assessment for rejection in heart transplant recipients, both adult and pediatric, is an imperative and urgent clinical need.

Organ-transplant patients require life-long immunosuppression that must be controlled carefully to balance risk of allograft rejection and loss with equally life-threatening immunosuppression-induced risks of infection, cancer, and other maladies. In heart transplant patients, this balance traditionally has been monitored through a multitude of diagnostic modalities.

A team of scientists led by those at the Medical College of Wisconsin (Milwaukee, WI, USA) clinically validated a rapid, highly sensitive, quantitative genotyping test using 158 matched endomyocardial biopsy-plasma pairs from 76 pediatric and adult heart transplant recipients. The test used is called the myTAIHEART (TAI Diagnostics, Wauwatosa, WI, USA) whose scientists cooperated in the study. From initial donor and recipient samples, the firm takes a baseline signature of 94 single nucleotide polymorphisms (SNPs) in genomic DNA (gDNA). It can then detect and quantify donor DNA in the transplant recipient's blood and calculate a donor fraction. These cell-free DNA (cfDNA) levels serve as a biomarker of viability, with rising donor fraction indicating a potential for transplant rejection.

To assure pre-analytical quality and consider interrelated cfDNA measures, plasma preparation was optimized and total cfDNA (TCF) concentration, DNA fragmentation, and donor-specific fraction (DF) quantification were validated in parallel for integration into myTAIHEART reporting. Analytical validations employed individual and reconstructed mixtures of human blood-derived gDNA, cfDNA, and gDNA sheared to apoptotic length. Precision, linearity, and limits of blank/detection/quantification were established for TCF concentration, DNA fragmentation ratio, and DF determinations.

For DF, multiplexed high-fidelity amplification followed by quantitative genotyping of 94 SNP targets was applied to 1,168 samples to evaluate donor options in staged simulations, demonstrating DF call equivalency with/without donor genotype. The clinical validation studies using 158 matched endomyocardial biopsy-plasma pairs from 76 pediatric and adult heart transplant recipients selected a DF cutoff (0.32%) producing 100% negative predictive value (NPV) for ≥2R acute cellular rejection (ACR).

Paula E. North, MD, PhD, a professor of pathology and lead author of the study, said, “The MyTAIHEART test can be used to stratify probability of moderate to severe ACR in heart transplant recipients. Another advantage is that the test is that it is a noninvasive test, which is particularly applicable in patients with limited vascular access, which is a relatively common problem in transplant patients. Furthermore, it can also be useful in stable patients after the first year post-transplant, and in patients who are too ill to undergo anesthesia and invasive biopsy. It is also a relatively inexpensive option compared to endomyocardial biopsy (EMB) that can potentially allow increased frequency of monitoring to detect rejection before it becomes clinically evident.” The study was published on January 13, 2020 in the journal PLOS ONE.

Related Links:
Medical College of Wisconsin
TAI Diagnostics



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