There are many testing options to choose from when trying to identify or confirm a genetic condition. The ideal test type for your patient will be determined by various factors including: clinical findings, cost, turnaround time, and why testing is being performed.
This blog will help you work through the different options available.
SINGLE GENE TEST
Single-gene tests are best used with a more defined phenotype that corresponds to 1 condition/gene. These tests help identify causative mutations and confirm the suspected diagnosis.
Example: Ordering beta-hemoglobin gene (HBB) analysis for someone who has clinical features with complete blood count or hemoglobin electrophoresis results consistent with beta-thalassemia and confirmation of causative mutations is desired.
In contrast, multi-gene panels are used to help narrow down a diagnosis in a more cost-effective and timely manner than testing one gene after another sequentially.
Example: Ordering a panel for congenital disorders of glycosylation (including 66 genes) on a patient with suspected clinical features of this type of disorder. Since the phenotypes can overlap, it is more cost effective to analyze many genes at once, instead of the top 3 or 4 as single-gene tests first.
Exome testing is the most comprehensive test available and is often used when there are more complex clinical presentations or when other testing has already shown to be negative. It has an average diagnostic yield of approximately 30%, but is more likely to return results of unknown significance than single and multi-gene testing.
Example: Patient symptoms/phenotype does not match any one diagnosis or set of diagnoses so exome testing is ordered to try and find the condition and cause (previous testing may have been done but would be negative).
Interested in an in-depth discussion about exome testing? Join us for a live webinar on Thursday, January 28th with EGL's Lora J.H. Bean, PhD, FACMG, Senior Molecular Laboratory Director and Lindsey C. Mighion, MS, CGC, Laboratory Genetic Counselor.
For more information regarding the Medical EmExome, download our clinician's guide to Medical EmExome testing.