Once upon a time, way back a decade ago, single gene testing often occurred during investigation of diseases. Those days are essentially over. Today, it’s all about multiple genes, gene expression tests, and much more. For an example, consider the numbers set out in this abstract of a June 10, 2019 paper about an investigation into Alzheimer’s and genetic variants:

“Design, Setting, and Participants  The discovery stage included 10 441 non-Hispanic white participants in the Alzheimer Disease Sequencing Project. Replication was sought in 2 independent, whole-exome sequencing data sets (1766 patients with AD, 2906 without AD [controls]) and a chip-based genotype imputation data set (8728 patients with AD, 9808 controls). Bioinformatics and functional analyses were conducted using clinical, cognitive, neuropathologic, whole-exome sequencing, and gene expression data obtained from a longitudinal cohort sample including 402 patients with AD and 647 controls. Data were analyzed between March 2017 and September 2018.”

Ma Y, Jun GR, Zhang X, et al. Analysis of Whole-Exome Sequencing Data for Alzheimer Disease Stratified by APOE Genotype. JAMA Neurol. Published online June 10, 2019. doi:10.1001/jamaneurol.2019.1456