Juston C Weems*, Deirdre Pierry, John Holman, Manoj Kandpal, Sunil M Kurian, Peter Meintjes, Neal Beswick and Josh Levitsky
Background: We have discovered and validated a microarray-based test that analyzes blood gene expression profiles (GEP) as an indicator of immune status in liver transplant recipients with stable liver function.
Methods: Analytical performance studies to characterize stability of RNA in blood during collection and shipment, analytical sensitivity (input RNA concentration), analytical specificity (interfering substances) and assay performance (clinical validity, and intra-assay, inter-assay, inter- laboratory reproducibility).
Results: Total RNA extracted from whole blood specimens collected in PAXgene Blood RNA tubes was stable up to 3 days at room temperature (stable RNA yield). Under routine ambient shipping conditions, storage and shipping temperatures did not affect results. However, specimen shipments exposed to temperatures >400°C or to ambient temperatures for >3 days were unacceptable for processing. Analytical sensitivity studies demonstrated tolerance to variation in RNA input (50 to 400 ng per 3’ IVT (in vitro transcript] labeling reaction). Specificity studies using genomic Jurkat DNA spiked into 3 ’IVT reactions at 10-20% demonstrated negligible assay interference. The test was reproducible across operators, runs, reagent lots, and laboratories. External validation demonstrated that the TruGraf Liver blood test accurately classified patients in 84% of 155 samples.
Conclusions: The previously published biomarker is the first non-invasive test to be demonstrated to have clinical utility in assessing immune status of LT recipients with stable liver function and shows promise as a reasonable and necessary tool supporting personalizing immunosuppressive therapy.
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