Understand whole-exome sequencing, when clinicians request it, how testing works, what affects cost and how to interpret the results.
What is WES in simple terms?
Whole-exome sequencing (WES) is a next-generation sequencing (NGS) test that examines most of the protein-coding regions of DNA. These regions, known as exons, account for a relatively small proportion of the human genome but contain many variants associated with recognized single-gene disorders. This makes WES useful when a condition may have several possible genetic explanations.
WES does not read the entire genome, nor does it cover every exon at equal quality. Its purpose is to investigate a defined clinical question, rather than provide a complete inventory of a person’s genetic differences.
When might WES be useful?
A clinician may consider WES when symptoms suggest more than one possible genetic disorder. Examples include some cases of childhood developmental delay, multisystem abnormalities, inherited neurological or muscle conditions, or unresolved cases after focused genetic tests. The decision depends on medical history, examination, family history and previous investigations.
If the suspected condition involves a balanced chromosomal rearrangement, a repeat expansion or a large structural change, karyotyping, chromosomal microarray analysis (CMA) or another targeted method may be more appropriate.
From sample collection to a report
Testing starts with clinical assessment, an agreed diagnostic question and informed consent. After an appropriate sample is collected, DNA is extracted, targeted regions are captured and sequenced. Bioinformatics specialists assess read quality, align sequences and identify potential variants.
The relevant findings are then prioritized against the patient’s symptoms and family history, classified and interpreted. A useful report explains what is clinically relevant, what remains uncertain and whether any follow-up testing is recommended.
What determines the cost of WES?
There is no universal price for whole-exome sequencing. Costs depend on whether one person or several family members are tested, coverage quality, laboratory methods, the scope of analysis, optional copy-number-variant analysis, confirmation of selected findings, interpretation and follow-up consultation.
Some quotations cover only sequencing, not a full clinical interpretation or later reanalysis. Ask how many people are included, what report you will receive, the expected turnaround time and who pays for any additional testing.
How should the result be read?
A report may identify a pathogenic or likely pathogenic variant relevant to symptoms, describe a variant of uncertain significance (VUS), or report no clear causal finding. A negative result does not definitively exclude a genetic disorder. Even a compelling finding must fit the clinical picture and expected inheritance pattern.
Some laboratories can also report medically actionable secondary findings under their consent and reporting policies. These choices should be discussed before testing.
Questions to ask before ordering
Ask the referring clinician what specific question WES should address. Could a more focused test be better? Would sequencing parents improve interpretation? Are earlier results available to avoid unnecessary duplication?
Confirm the accepted sample, coverage expectations, consent policy for secondary findings, reporting scope and possible reanalysis. WES is most valuable when test selection, laboratory methods, data analysis and clinical interpretation work together.
Frequently asked questions
Is WES the same as WGS?
No. WES primarily targets coding regions, while whole-genome sequencing (WGS) examines a broader portion of the genome. Neither detects every possible type of genetic change.
Does WES always provide a diagnosis?
No. Technical limitations, variant type and gaps in current medical knowledge may prevent a definitive answer.
Scientific resources for further reading
For case-specific advice and current laboratory requirements, consult our services or genetic counseling team.
