Blood-Based Gene Expression Tests

Abstract

The tremendous progress achieved in the omics field has successfully provided new insights into the pathogenesis of common diseases. Molecular phenotyping of the disease status has become feasible by novel, robust, and fast high-throughput analytic platforms, and global gene expression profiling offers a novel opportunity for molecular disease profiling and biomarker identification. Article see p 154 A biomarker is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention, and the overall expectation of a biomarker is to enhance the ability of the clinician to optimally manage the patient.1 To evaluate a biomarker, important measures are its sensitivity (ability to detect the disease, ie, identification of true-positives) and specificity (ability to the detect absence of disease, ie, identification of true-negatives), as well as its positive and negative predictive values.1 Expression pattern of defined genes can also be viewed as a biomarker in which the expression levels of multiple genes are combined in a defined manner to provide an expression signature, an expression score, or a classifier. A precise gene expression signature or score has the promise to diagnose diseases, classify them further, and potentially guide personalized decisions for individual patients. Because of their easy accessibility, whole blood and peripheral blood mononuclear cells provide an optimal source for RNA and subsequent gene expression analyses. Gene expression profiling has already been shown to predict cardiomyopathy pathogenesis in heart failure2,3 and to be useful in monitoring clinically significant allograft rejection.4,5 …