AlloMap Molecular Expression Test
In August 2008, the AlloMap Molecular ExpressionTest, made by XDx Expression Diagnostics was licensed as a multigene blood test for use in heart-transplant patients. AlloMap Testing is intended to aid in the identification of heart transplant recipients with stable allograft function who have a low probability of moderate or severe acute cellular rejection. The test is approved for use in patients who are 15 years of age or older and are at least two months (55 days or longer) post-transplantation.
AlloMap assesses the gene-expression profile of RNA isolated from peripheral blood mononuclear cells (PBMCs). AlloMap detects expression of 20 genes, 11 informative and nine are used for normalization and quality control. PBMCs are lyzed to release RNA which is then converted into cDNA. The expression of each gene is measured by amplification and fluorescence detection using a qRT-PCR.
A mathematical classifier combines the measured gene expression values into a single AlloMap score between 0 and 40. Each score is associated with a negative predictive value (NPV) and a positive predictive value (PPV), that indicate the probability that the patient does not have or does have current rejection.
Clinical validation of the AlloMap test used patient samples and clinical data obtained during the Cardiac Allograft Rejection Gene Expression Observational (CARGO) study. Nine U.S. heart transplant centers enrolled 737 patients who contributed 5,834 blood samples and clinical data. This study confirmed the efficacy and performance of the AlloMap test.
A comparative effectiveness study, the Invasive Monitoring Attenuation through Gene Expression (IMAGE) study, compared clinical outcomes of patients managed with AlloMap to clinical outcomes of patients managed with endomyocardial biopsy. U.S. heart transplant centers enrolled 602 patients who were at least six months post-transplant. The results showed that AlloMap was not inferior to endomyocardial biopsy with respect to clinical outcomes when used to monitor stable, asymptomatic heart transplant patients.
