Home Molecular Testing Methods Multigene Panel Test: Inherited Disease Genes, Cancer Genes, and Results

Multigene Panel Test: Inherited Disease Genes, Cancer Genes, and Results

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Vita Library
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Multigene panel testing analyzes inherited disease and cancer genes together; learn how panel selection, coverage, pathogenic variants, VUS findings, and negative results are interpreted.

A multigene panel test analyzes several or many genes at the same time. It is useful when different genes can cause overlapping symptoms or when a personal and family history could fit more than one hereditary cancer syndrome. Panels may contain fewer than ten genes or several hundred, and they differ in gene selection, sequencing coverage, deletion/duplication analysis, repeat or pseudogene methods, and reporting policy. More genes do not automatically make a better test. A broad panel can increase the chance of finding the cause, but it also increases uncertain and unexpected findings, particularly when genes have limited evidence or management guidance. The test may use blood, saliva, or another constitutional specimen to look for inherited variants, while a tumor panel evaluates acquired cancer changes and may not establish germline status. Results are generally classified as pathogenic, likely pathogenic, uncertain, likely benign, or benign. A positive result must fit the gene’s inheritance pattern and disease relationship. A negative result may be uninformative if the wrong genes, variant types, or family member were tested.

  • Multigene panels are most useful when several well-established genes could explain the same clinical question.
  • Panel content, coverage, and deletion/duplication capability vary substantially among laboratories.
  • Germline panels and tumor panels analyze different biological questions, even when gene names overlap.
  • Pathogenic and likely pathogenic variants may guide diagnosis, surveillance, treatment, or family testing.
  • A variant of uncertain significance should not be used alone for irreversible medical decisions.
  • A negative panel does not eliminate genetic risk when family history or phenotype remains strong.

Table of Contents

What Multigene Panels Are

A multigene panel is a curated group of genes analyzed for a defined clinical indication. The genes may be linked by phenotype, organ system, biochemical pathway, tumor type, or hereditary-risk pattern. Examples include epilepsy, cardiomyopathy, hearing loss, renal disease, connective-tissue disorders, mitochondrial disease, hereditary breast and ovarian cancer, polyposis, and broad hereditary cancer panels.

Most panels use next-generation sequencing to read coding exons and selected nearby intronic bases. Many add copy-number analysis to detect exon-level or whole-gene deletions and duplications. Some include specialized assays for repeat expansions, difficult pseudogene regions, methylation, mitochondrial DNA, or structural variants. The term “panel” does not guarantee that every relevant variant class is covered.

A germline panel usually analyzes constitutional DNA from blood, saliva, or another non-tumor source. It asks whether a person carries an inherited or de novo variant present throughout the body. A tumor panel analyzes cancer tissue or circulating tumor DNA and mainly identifies acquired alterations that may guide treatment. A variant found in tumor can be germline, but tumor testing alone may not distinguish the source. ASCO guidance states that patients who meet criteria for germline testing should receive appropriate germline testing regardless of tumor-testing results [1].

Panels occupy a middle ground between single-gene testing and exome or genome sequencing. They can provide deeper coverage and more focused interpretation than exome testing, while avoiding genes unrelated to the clinical question. However, a fixed panel can become outdated as new gene-disease relationships are established. Some laboratories use an exome backbone and analyze only the ordered virtual panel, allowing later reanalysis without generating a new sample.

The clinical value depends on gene-disease validity. A gene should be included because credible human evidence links pathogenic variation in that gene to the condition being evaluated, not merely because the gene has an appealing biological role. ClinGen systematically assesses the strength of gene-disease relationships and separates definitive or strong evidence from limited, disputed, or refuted claims [2]. Panels containing poorly established genes create more uncertain findings without necessarily improving diagnosis.

When a Panel Is the Right Test

A panel is especially useful when several genes produce similar features and clinical examination cannot reliably select one. Hypertrophic cardiomyopathy, inherited retinal disease, epilepsy, hearing loss, and hereditary cancer are common examples. Testing genes in parallel can save time, tissue, and cost compared with sequential single-gene tests.

A focused panel may be preferable when the phenotype is distinctive and the relevant gene set is well defined. A broader panel may be reasonable when features overlap several syndromes, family history is limited, ancestry or adoption obscures risk, or the result could affect multiple aspects of management. The panel should be broad enough to address plausible diagnoses but not so broad that it introduces many genes unrelated to the question.

In hereditary cancer, panel selection should be based on the cancer type, age at diagnosis, pathology, family structure, ancestry, and cancers on both sides of the family. A person with breast and pancreatic cancer in close relatives may need a different panel from someone with numerous colorectal polyps or diffuse gastric cancer. The 2024 ASCO guideline recommends considering personal and family history when choosing the panel and including genes with established management relevance for the clinical scenario [1].

Testing an affected relative is usually more informative than testing an unaffected relative. If a family has multiple cancers, the best initial candidate may be the person with the youngest diagnosis, rarest tumor, multiple primary cancers, or most syndrome-specific features. A negative result in an unaffected person can be difficult to interpret when no familial pathogenic variant is known.

A panel may be less appropriate when:

  • one familial pathogenic variant is already known, making targeted testing sufficient;
  • a characteristic biochemical or methylation test should come first;
  • the likely condition is caused mainly by a repeat expansion or structural mechanism not covered by the panel;
  • chromosomal abnormalities are suspected and microarray or karyotype is more suitable;
  • the phenotype is so broad that exome or genome sequencing with family samples is likely to be more efficient.

Pretest counseling should define the possible outcomes and what decisions each could change. Testing simply because a large panel is available can generate information without a clear clinical use.

Choosing Genes and Technical Coverage

Two panels with similar names may have very different contents. Review the exact gene list and the disease association assigned to each gene. For inherited disease, ask whether the gene is associated with the patient’s phenotype and whether the inheritance pattern fits the family. For cancer, distinguish high-penetrance genes with established surveillance from moderate-risk genes and genes with uncertain or emerging risk estimates.

Technical coverage is equally important. A panel description should state:

  • which transcripts and exons are analyzed;
  • the intronic boundary included around each exon;
  • whether deletion/duplication analysis is performed;
  • whether promoter, deep intronic, or regulatory regions are included;
  • how low-coverage regions are completed;
  • whether mosaic variants can be detected and at what level;
  • whether difficult genes, pseudogenes, repeats, or homologous regions require special methods;
  • whether mitochondrial DNA or copy-number-neutral mechanisms are assessed.

Some important genes are technically challenging. PMS2 has homologous pseudogene regions; SMN1 and SMN2 require copy-number and gene-conversion analysis; CYP21A2 has a nearby pseudogene; repeat-expansion disorders cannot be excluded by ordinary short-read sequencing; and exon-level deletions may be missed if dosage analysis is absent. A panel that lists the gene but lacks the required method may provide false reassurance.

Deletion and duplication analysis can use read-depth algorithms, MLPA, array, quantitative PCR, or another validated method. The deletion/duplication test guide explains why sequence analysis alone may not detect exon-level dosage variants. Laboratories should disclose regions where copy-number sensitivity is reduced.

Panel size affects the balance between diagnostic yield and uncertainty. Adding clinically relevant genes can identify unexpected but actionable diagnoses. Adding genes with weak evidence raises the chance of VUS findings and ambiguous risk. ASCO and other professional guidance increasingly emphasizes purposeful panel construction rather than using the largest available menu [1,3].

The consent process should also address secondary or incidental findings. A focused panel usually limits these, but a broad multisystem panel can identify a pathogenic variant unrelated to the original reason for testing. Laboratories differ in whether such findings are reported and whether patients can opt out.

Specimens and Laboratory Analysis

Blood is often the preferred germline specimen because it yields high-quality DNA. Saliva or buccal samples are convenient but can contain variable DNA amounts, microbial DNA, and blood-cell contamination. In people with hematologic malignancy, prior stem-cell transplant, active clonal hematopoiesis, or recent transfusion, blood may not represent the intended constitutional genome. Cultured skin fibroblasts or another nonhematopoietic specimen may be needed.

The laboratory extracts DNA, prepares sequencing libraries, captures or amplifies targeted regions, and sequences them at validated depth. Bioinformatic software aligns reads to a reference genome and calls single-nucleotide variants and small insertions or deletions. Copy-number algorithms compare read depth across exons, often followed by orthogonal confirmation.

Quality metrics include the proportion of target bases above a minimum depth, read quality, allele balance, strand support, and sample identity. Regions that fail coverage may be completed by Sanger sequencing or listed as limitations. A high average depth does not guarantee complete coverage of every exon.

Variant interpretation uses population frequency, predicted molecular effect, segregation, functional data, case evidence, phenotype match, inheritance, and expert-curated resources. Variants are classified under professional frameworks as pathogenic, likely pathogenic, uncertain significance, likely benign, or benign. Laboratories may differ because they have different internal data, evidence dates, or application of criteria.

The report should identify the genes analyzed, test limitations, reportable range, and classification date. It may include only pathogenic, likely pathogenic, and uncertain variants relevant to the indication, while omitting benign changes. A “negative” report therefore does not mean no DNA differences were found; it means no reportable disease-associated variants met the laboratory’s criteria.

Turnaround time varies with panel size, confirmatory testing, specimen quality, and whether parental samples are analyzed. Trio or family-based testing can improve interpretation by showing whether variants are de novo, inherited, or located on opposite chromosome copies.

Interpreting Positive Results

A positive result usually means a pathogenic or likely pathogenic variant was identified in a gene relevant to the clinical question. The result is diagnostic only when the gene-disease relationship, inheritance pattern, variant state, and phenotype align.

For an autosomal dominant disorder, one pathogenic variant may be sufficient. For an autosomal recessive disorder, two pathogenic variants usually must be present on opposite copies of the gene. If two variants are found but phase is unknown, testing parents can determine whether they are in trans or on the same chromosome. For an X-linked condition, interpretation depends on sex-chromosome complement, gene, and X-inactivation or penetrance. Mitochondrial inheritance follows separate rules.

In hereditary cancer, a pathogenic variant can affect surveillance, preventive surgery discussions, treatment, and relatives. The magnitude and spectrum of risk vary by gene and sometimes by variant. A pathogenic BRCA1 variant and a pathogenic variant in a moderate-risk breast cancer gene should not trigger identical recommendations. Management should follow current gene-specific guidance.

A positive result can be:

  • Diagnostic: it explains the person’s clinical condition.
  • Predictive: an unaffected person carries a familial risk variant.
  • Carrier: one recessive disease variant is present without confirming the disease.
  • Incidental: a medically important finding is unrelated to the test indication.
  • Potentially mosaic: the variant is present at an allele fraction below that expected for a standard germline heterozygous result.

The report may describe reduced penetrance or variable expressivity. Reduced penetrance means not every carrier develops the condition. Variable expressivity means affected carriers can have different features or severity. A positive result predicts risk, not an exact future.

When a variant was first found on tumor testing, confirmation in a constitutional specimen is essential before relatives are tested. A tumor VAF near 50% is not proof of germline origin because tumor purity, copy number, loss of heterozygosity, and clonal hematopoiesis can produce similar values.

A result should be connected to a care plan: disease-specific evaluation, surveillance, treatment consideration, reproductive counseling, or targeted family testing. The presence of a pathogenic variant alone does not replace clinical judgment.

Variants of Uncertain Significance

A VUS is a DNA change for which available evidence cannot establish whether it causes disease. It is neither a positive nor a negative result. Larger panels generate more VUS findings because they examine more genes and include more rare variation.

A VUS should not be used alone to diagnose a condition, recommend preventive surgery, change cancer screening beyond what personal and family history supports, or test healthy relatives predictively. Clinical management should be based on established risk factors while the variant remains uncertain.

Several kinds of evidence may later clarify a VUS:

  • population data showing the variant is too common for the disorder;
  • segregation with or away from disease in informative relatives;
  • well-validated functional studies;
  • repeated observation in people with a consistent phenotype;
  • RNA analysis showing an effect on splicing;
  • expert-panel classification;
  • improved knowledge of the gene-disease relationship.

Testing relatives solely “to see who has the VUS” is often uninformative. A laboratory or genetics professional may recommend targeted segregation testing when specific relatives can provide meaningful evidence. The laboratory should guide this process.

VUS rates vary by ancestry because reference databases contain unequal representation. People from underrepresented populations may receive more uncertain findings even when their true disease risk is no higher. This is a limitation of available evidence, not a biological difference in the meaning of uncertainty.

Laboratories periodically reclassify variants. Most VUS reclassifications move toward benign or likely benign, although some become pathogenic. Patients should keep contact information current and retain the report. The ordering clinic should have a plan for receiving and communicating amended results.

A VUS in a gene with limited disease validity is even harder to interpret. Stronger gene-disease curation and careful panel design reduce this problem. ClinGen’s evidence-based framework is one resource laboratories and clinicians use to judge whether variation in a gene can credibly cause a specific disorder [2].

Negative and Inconclusive Results

A negative panel means no reportable pathogenic or likely pathogenic variant was found in the genes and regions analyzed. Its significance depends on the pretest probability and whether the test could detect the relevant mechanism.

A true negative occurs when a familial pathogenic variant is known and the tested relative does not carry it. This usually returns that person’s risk for the associated hereditary syndrome toward population or family-history-based levels, while unrelated risks remain.

An uninformative negative occurs when no familial cause is known. The family may have a variant in an untested gene, a variant type the assay cannot detect, a polygenic or multifactorial cause, or a non-genetic explanation. Screening may still be recommended based on family history.

A negative result may require reconsideration when:

  • the panel omitted a relevant gene;
  • copy-number analysis was not included;
  • repeat expansions, methylation, mitochondrial variants, or structural changes were not assessed;
  • the tested person was unaffected while an affected relative is available;
  • the phenotype has evolved or was entered incompletely;
  • a gene-disease association was established after the test;
  • exome or genome sequencing could evaluate a broader hypothesis.

An inconclusive report may contain one pathogenic variant in a recessive gene when a second is required, two variants with unknown phase, a VUS that fits the phenotype, or a technical limitation in a critical region. These findings can guide follow-up but do not confirm the diagnosis.

Reanalysis can be valuable. A laboratory may reinterpret stored data as classifications and gene lists change. Sometimes a new panel, exome, genome, RNA study, or chromosome-level test is more appropriate than reanalyzing the same restricted data.

Negative hereditary cancer testing does not erase risk from prior cancers, atypical pathology, or strong family history. Risk models and enhanced screening may still apply. Likewise, a negative diagnostic panel does not mean symptoms are psychological or unexplained forever; it marks the limit of current testing.

Family Testing and Follow-Up

When a pathogenic germline variant is identified, relatives can receive targeted testing for that exact familial change. Targeted testing is more informative and usually less expensive than repeating the full panel. Results divide relatives into carriers and noncarriers for that variant, allowing surveillance and reproductive counseling to be individualized.

Cascade testing should begin with close adult relatives and expand according to the inheritance pattern. Testing minors is generally appropriate when childhood management would change; adult-onset-only risks usually warrant deferring predictive testing until the person can participate in the decision. Exceptions depend on the gene and family situation.

Reproductive implications vary. Autosomal recessive carrier couples may have a 25% chance of an affected child in each pregnancy. An autosomal dominant carrier often has a 50% chance of transmitting the variant, but penetrance may be incomplete. X-linked and mitochondrial risks require separate counseling. Options can include prenatal diagnosis, preimplantation genetic testing, donor gametes, or natural conception with postnatal testing.

After receiving a report, ask:

  1. Were the genes appropriate for the phenotype and family history?
  2. Did the assay include deletion/duplication analysis and other relevant variant types?
  3. Does a positive variant fit the inheritance pattern and clinical features?
  4. Is a result germline, tumor-only, or potentially mosaic?
  5. Should parents, siblings, children, or another affected relative be tested?
  6. What management is supported by current gene-specific guidance?
  7. How will reclassification or reanalysis be communicated?

Genetic counseling improves test selection, consent, interpretation, and family communication. It is particularly important for broad panels, moderate-risk cancer genes, uncertain variants, unexpected findings, and reproductive decisions.

Keep the complete report and the exact variant notation. Family members should provide a copy to their own clinician rather than relying on a verbal gene name. A well-chosen multigene panel can shorten a diagnostic journey or identify preventable risk, but its value comes from matching the right genes and methods to the clinical question and translating the result into proportionate care.

References

Disclaimer

This article provides general education and cannot select a panel or interpret an individual germline or tumor result. Gene lists, evidence, and management guidance change, so decisions should use the complete laboratory report and consultation with a genetics professional. A VUS should not be used by itself for preventive surgery, predictive family testing, or other irreversible action.

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