PGxome® - Whole Exome Sequencing

Test Requisition Form

PGxome® RAPID Exome Test

Name Test Code Description CPT Code(s) Price
Family - Trio 13003 WES of patient + 2 additional family members 81415, 81416(x2) $2,890

If report is needed for any additional family members, add $490 per family member.

Family - Duo 13002 WES of patient + 1 additional family member 81415, 81416 $2,690

If report is needed for any additional family members, add $490 per family member.

Patient Only 13001 WES of patient 81415 $2,290

Sequencing cost to additional family members beyond trio: $390 (no report); additional CPT Code 81416

Rapid PGxome - Diagnostic is ideal for:

  • Seriously ill patients with an urgent need for genetic diagnosis

What is Rapid PGxome Diagnostic?

PGxome is PreventionGenetics' whole exome sequencing (WES) test. The PGxome assesses almost all genes from the human genome including coding regions and adjacent introns. This test is an appropriate choice for health care providers who are looking for an urgent genetic diagnosis. This is important as more than 50% of patients with genetic diseases are not given a specific diagnosis even after repeat clinical examinations and tests (Shashi et al. 2014). The standard clinical practice often involves examinations for specific phenotypes, imaging, biochemical testing for inborn errors of metabolism, genomic tests such as karyotyping or microarrays, and single gene or panel tests (Iglesias et al. 2014). However, patients remain without a genetic diagnosis, and patients and health care providers are caught in a long term diagnosis search, known as a diagnostic odyssey. This can lead to failures in identifying potential treatments and unknown recurrence and prognosis risks (Yang et al. 2013).

Reported diagnostic rates from commercial and academic laboratories have found that WES assays have a ~20-40% positive diagnostic rate, with higher rates being reported from trio analysis (i.e. proband and parents) compared to singleton analysis (Atwal et al. 2014; Iglesias et al. 2014; Farwell et al. 2015). Notably, ~5-7% of individuals who have WES have had dual diagnoses (i.e. two non-overlapping clinical presentations) (Yang et al. 2014; Farwell et al. 2015; Posey et al. 2016). The inclusion of copy number variant (CNV) calling should increase diagnostic rates. One study reported that 30% of genetics diagnoses have only been recently resolved due to new literature reports, highlighting the fast pace of gene-disease discovery, and the need of genetic testing laboratories to be current of the medical literature (Yang et al. 2014). The use of a whole exome sequencing test may aid in altering clinical management, predict recurrence and prognosis risks, reduce costs of additional testing, and may offer advantages over traditional molecular tests in certain patients (Valencia et al. 2015).

Rapid PGxome - Diagnostic is ideal for:

  • Seriously ill patients with an urgent need for genetic diagnosis

TURN AROUND TIME (TAT)

Rapid PGxome has an expedited TAT of 13 calendar days on average.

We recommend that providers choose expedited shipping to decrease the time samples spend in transit to PreventionGenetics.

Inclusion of detailed clinical notes/completion of the clinical data checklist and a pedigree are required. The ability to select variants that may be involved with the patient’s health problem directly correlates with the quality of clinical information provided.

ORDERING / SPECIMENS

Our Rapid PGxome Diagnostic offers the traditional options of Patient Only testing or Family testing (e.g., Duo, Trio, etc.). For the highest diagnostic rate, Family - Trio testing is recommended.

Specimen Requirements and Shipping Details

 

TEST METHODS

For the PGxome we use Next Generation Sequencing (NGS) technologies to cover the coding regions of targeted genes plus ~10 bases of non-coding DNA flanking each exon. As required, genomic DNA is extracted from patient specimens. Patient DNA corresponding to these regions is captured using hybridization probes. Captured DNA is sequenced on the NovaSeq 6000 using 2x150 bp paired-end reads (Illumina, San Diego, CA, USA). The following quality control metrics are generally achieved: >97% of target bases are covered at >20x, and mean coverage of target bases >100x. Data analysis and interpretation is performed by the internally developed Infinity pipeline. Variant calls are made by the GATK Haplotype caller and annotated using in house software and Jannovar. Common benign, likely benign, and low quality variants are filtered from analysis.

Copy number variants (CNVs) are also detected from NGS data. We utilize a CNV calling algorithm that compares mean read depth and distribution for each target in the test sample against multiple matched controls. Neighboring target read depth and distribution and zygosity of any variants within each target region are used to reinforce CNV calls. All reported CNVs are confirmed using another technology such as aCGH, MLPA, or PCR.

REPORTING

Only primary findings will be reported for Rapid PGxome. Reports will consist of up to two sections:

  • Variants in genes known to be associated with phenotype
  • Variants in genes possibly associated with phenotype

A preliminary report prior to confirmation may be issued in cases with a clear positive finding.

Secondary findings are not reported.

All differences from the reference sequences (sequence variants) are assigned to one of five interpretation categories (pathogenic, likely pathogenic, variant of uncertain significance, likely benign and benign) per ACMG guidelines (Richards et al. 2015). Only relevant pathogenic, likely pathogenic, and Uncertain variants are reported. likely benign and benign variants are not included in the reports. A full list of all sequence variants will be provided to the ordering physician upon request.

Nomenclature for sequence variants comes from Human Genome Variation Society (HGVS) (http://www.hgvs.org).

LIMITATIONS AND OTHER TEST NOTES

Interpretation of the test results is limited by the information that is currently available. Better interpretation should be possible in the future as more data and knowledge about human genetics and this specific disorder are accumulated.

Sequencing: When sequencing does not reveal any heterozygous differences from the reference sequence, we cannot be certain that we were able to detect both patient alleles.

For technical reasons, the PGxome test is not 100% sensitive. Some exons cannot be efficiently captured, and some genes cannot be accurately sequenced because of the presence of multiple copies in the genome. Therefore, a small fraction of sequence variants relevant to the patient's health will not be detected.

We sequence coding exons for most given transcripts, plus ~10 bp of flanking non-coding DNA for each exon. Unless specifically indicated, test reports contain no information about other portions of the gene, such as regulatory domains, deep intronic regions, uncharacterized alternative exons, chromosomal rearrangements, repeat expansions, epigenetic effects, and mitochondrial genome variants.

In most cases, we are unable to determine the phase of sequence variants. In particular, when we find two likely causative mutations for recessive disorders, we cannot be certain that the mutations are on different alleles.

The ability to detect low-level mosaicism of variants is limited.

Runs of mononucleotide repeats (eg (A)n or (T)n) with n >8 in the reference sequence are generally not analyzed because of strand slippage during amplification.

Unless otherwise indicated, DNA sequence data is obtained from a specific cell-type (usually leukocytes if taken from whole blood). Test reports contain no information about the DNA sequence in other cell-types.

We cannot be certain that the reference sequences are correct.

Copy Number Variant Analysis: The PGxome test detects most deletions and duplications including intragenic CNVs and large cytogenetic events; however aberrations in a small percentage of regions may not be accurately detected due to sequence paralogy (e.g., pseudogenes, segmental duplications), sequence properties, deletion/duplication size (e.g., 1-3 exons vs. 4 or more exons), and inadequate coverage. In general, sensitivity for single, double, or triple exon CNVs is ~70% and for CNVs of 4 exons or larger is >95% but may vary from gene-to-gene based on exon size, depth of coverage, and characteristics of the region.

Balanced translocations or inversions are only rarely detected.

Certain types of sex chromosome aneuploidy may not be detected.

In nearly all cases, our ability to determine the exact copy number change within a targeted region is limited.

Our ability to detect CNVs due to somatic mosaicism is limited.

The sensitivity of this test is dependent on DNA quality.

CONTACTS

Genetic Counselors: GC Team - support@preventiongenetics.com

Geneticist: Diane Allingham-Hawkins, PhD, FCCMG, FACMG - diane.allingham-hawkins@preventiongenetics.com

REFERENCES

Atwal P.S. et al. 2014. Genetics in Medicine : Official Journal of the American College of Medical Genetics. 16: 717-9. PubMed ID: 24525916

Caudle et al. 2016. Genetics in Medicine. PubMed ID: 27441996

Farwell K.D. et al. 2015. Genetics in Medicine : Official Journal of the American College of Medical Genetics. 17: 578-86. PubMed ID: 25356970

Iglesias A. et al. 2014. Genetics in Medicine : Official Journal of the American College of Medical Genetics. 16: 922-31. PubMed ID: 24901346

Kalia S.S. et al. 2016. Genetics in Medicine: Official Journal of the American College of Medical Genetics. Advance online publication. doi:10.1038/gim.2016.190. PubMed ID: 27854360

Posey et al. 2016. Genetics in Medicine : Official Journal of the American College of Medical Genetics. 18: 678-85. PubMed ID: 26633545

Richards S et al. 2015. Genetics in Medicine : Official Journal of the American College of Medical Genetics. 17: 405-24. PubMed ID: 25741868

Shashi V. et al. 2014. Genetics in Medicine : Official Journal of the American College of Medical Genetics. 16: 176-82. PubMed ID: 23928913

Valencia C.A. et al. 2015. Frontiers in Pediatrics. 3: 67. PubMed ID: 26284228

Yang Y. et al. 2013. The New England Journal of Medicine. 369: 1502-11. PubMed ID: 24088041

Yang Y. et al. 2014. JAMA. 312: 1870-9. PubMed ID: 25326635