WES vs. CMA: Understanding the Difference

In the ever-evolving landscape of genetics, diagnostic tools play a pivotal role. Two such prominent tools are Whole Exome Sequencing (WES) and Chromosomal Microarray (CMA), each serving unique diagnostic purposes.

Whole Exome Sequencing (WES) focuses on the protein-coding regions of the genome, known as the exome. While the exome only makes up about 1-2% of the genome, it contains approximately 85% of known disease-causing mutations. WES is particularly effective for identifying single nucleotide variants and small insertions or deletions.

Chromosomal Microarray Analysis (CMA)

On the other hand, Chromosomal Microarray Analysis (CMA) is designed to detect larger genomic imbalances, such as copy number variants (CNVs). These include microdeletions and microduplications that may be too small to be seen under a microscope but too large to be detected by traditional sequencing methods.

Choosing the Right Test

The choice between WES and CMA depends on the clinical presentation and the suspected underlying genetic cause. Often, CMA is used as a first-tier test for individuals with developmental delays or multiple congenital anomalies, while WES is employed when a specific single-gene disorder is suspected or when first-tier tests have not provided a diagnosis.