Analytical Validation of HEARTBiT: A Blood-Based Multiplex Gene Expression Profiling Assay for Exclusionary Diagnosis of Acute Cellular Rejection in Heart Transplant Patients.

BACKGROUND: HEARTBiT is a whole blood-based gene profiling assay using the nucleic acid counting NanoString technology for the exclusionary diagnosis of acute cellular rejection in heart transplant patients. The HEARTBiT score measures the risk of acute cellular rejection in the first year following heart transplant, distinguishing patients with stable grafts from those at risk for acute cellular rejection. Here, we provide the analytical performance characteristics of the HEARTBiT assay and the results on pilot clinical validation. METHODS: We used purified RNA collected from PAXgene blood samples to evaluate the characteristics of a 12-gene panel HEARTBiT assay, for its linearity range, quantitative bias, precision, and reproducibility. These parameters were estimated either from serial dilutions of individual samples or from repeated runs on pooled samples. RESULTS: We found that all 12 genes showed linear behavior within the recommended assay input range of 125 ng to 500 ng of purified RNA, with most genes showing 3% or lower quantitative bias and around 5% coefficient of variation. Total variation resulting from unique operators, reagent lots, and runs was less than 0.02 units standard deviation (SD). The performance of the analytically validated assay (AUC = 0.75) was equivalent to what we observed in the signature development dataset. CONCLUSION: The analytical performance of the assay within the specification input range demonstrated reliable quantification of the HEARTBiT score within 0.02 SD units, measured on a 0 to 1 unit scale. This assay may therefore be of high utility in clinical validation of HEARTBiT in future biomarker observational trials.

The association of polymorphism in PHACTR1 rs9349379 and rs12526453 with coronary artery atherosclerosis or coronary artery calcification. A systematic review.

OBJECTIVE: There is a need to identify genetic factors that may produce coronary artery atherosclerotic disease (CAD) that are not involved in the usual risk factors leading to CAD. Previous studies have often equated coronary artery calcification (CAC) with CAD with coronary stenosis or its sequelae. The objective of this study was to examine the relationship between phosphatase and actin regulator 1 (PHACTR1) single nucleotide polymorphisms (SNPs) and the type of coronary artery disease CAD versus CAC. METHOD: A systematic review of the literature was conducted to answer the question of whether PHACTR1 gene polymorphisms are associated with coronary artery disease expressed as coronary artery atherosclerosis or CAC. RESULTS: Eighteen studies spanning seven PHACTR1 SNPs were identified and evaluated for the relationship between PHACTR1 and coronary artery disease. There were significant relationships between rs9349379, rs12526453, and CAD with odds ratios (ORs) (confidence interval) of, respectively, 1.15 (1.13-1.17), 1.13 (1.09-1.17) but not for rs2026458, 1.03 (0.88-1.19). The OR for CAC was 1.22 (1.18-1.26) for rs9349379 and 1.28 (1.21-1.38) for rs12526453. CONCLUSIONS: Several PHACTR1 specifically rs9349379 and rs12526453 polymorphisms but not rs2026458, are associated with CAD. There are differences in the association of PHACTR1 SNPs with CAC. PHACTR1 warrants more attention and study for the prevention and treatment of CAD.