Microcephaly and Pontocerebellar Hypoplasia Panel

48 gene panel that includes assessment of non-coding variants

Ideal for patients with a clinical suspicion of microcephaly or pontocerebellar hypoplasias.

Analysis methods Availability Number of genes Test code CPT codes
PLUS
SEQ
DEL/DUP
4 weeks 48 GHC0217 SEQ 81405
SEQ 81406
SEQ 81407
DEL/DUP 81479

Summary

ICD codes
Commonly used ICD-10 code(s) when ordering the Microcephaly and Pontocerebellar Hypoplasia Panel

ICD-10 Disease
Q02 Microcephaly
Q04.3 Pontocerebellar hypoplasias

Sample requirements:

  • EDTA blood, min. 1 ml
  • Purified DNA, min. 3μg
  • Saliva (Oragene DNA OG-500 kit)

Label the sample tube with your patient’s name, date of birth and the date of sample collection. Note that we do not accept DNA samples isolated from formalin-fixed paraffin-embedded (FFPE) tissue.

About

Microcephaly is a neurodevelopmental disorder. It is usually defined as a head circumference (HC) more than two (or three) standard deviations below the mean for age and sex and serves as an important neurological indication or warning sign, however uniformity in its definition is lacking. Microcephaly may be congenital or develop in the first few years of life. In general, life expectancy for individuals with microcephaly is reduced and the prognosis for normal brain function is poor. It may stem from a wide variety of conditions that cause abnormal growth of the brain, or from syndromes associated with chromosomal abnormalities. A homozygous mutation in one of the microcephalin genes (MCPH1, ASPM, WDR62) causes primary microcephaly. Najm type X-linked intellectual deficit (point mutations and deletions in the CASK gene) is a rare cerebellar dysgenesis syndrome associated with microcephaly in most cases. Examples of monogenic syndromes associated with microcephaly are Seckel syndrome spectrum disorders. Nonsyndromic pontocerebellar hypoplasias (PCH) are a rare heterogeneous group of diseases characterized by hypoplasia and atrophy and/or early neurodegeneration of the cerebellum and pons. PCH patients of all subtypes present with progressive microencephaly, delayed or absence of cognitive and voluntary motor development, intellectual deficit, spasticity, chorea/dyskinesia, swallowing difficulties and seizures. The majority of PCH cases are caused by mutations in tRNA splicing endonuclease (TSEN genes). Approximately half the cases of PCH subtype 1 are due to mutations in the EXOSC3 gene. Other subtypes include mutations in for example TSEN2 and TSEN54 genes. Diagnosis is made based on clinical symptoms and neuroradiological findings (MRI) and can be confirmed by molecular genetic analyses. Nonsyndromic pontocerebellar hypoplasias (PCH) are generally inherited in an autosomal recessive pattern. Isolated microcephaly is known to have autosomal dominant, autosomal recessive and X-linked inheritance.

Panel Content

Genes in the Microcephaly and Pontocerebellar Hypoplasia Panel and their clinical significance

Gene Associated phenotypes Inheritance ClinVar HGMD
AKT3Megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndromeAD1227
AMPD2Pontocerebellar hypoplasia type 9, Spastic paraplegia 63AR1415
ASPMMicrocephalyAR171174
ATRCutaneous telangiectasia and cancer syndrome, Seckel syndromeAD/AR818
CASKMental retardation and microcephaly with pontine and cerebellar hypoplasia, FG syndrome, Mental retardationXL80104
CDK5RAP2MicrocephalyAR1920
CENPFCiliary dyskinesia -Lethal CiliopathyAR127
CENPJSeckel syndrome, MicrocephalyAR329
CEP63Seckel syndromeAR72
CEP152Seckel syndrome, MicrocephalyAR1920
DYNC1H1Spinal muscular atrophy, Charcot-Marie-Tooth disease, Mental retardationAD5764
DYRK1AMental retardationAD8777
EFTUD2Mandibulofacial dysostosis with microcephaly, Esophageal atresia, syndromicAD4393
EXOSC3Pontocerebellar hypoplasiaAR1219
GFM1Combined oxidative phosphorylation deficiencyAR1818
KANSL1Koolen-de Vries syndromeAD5463
KATNB1Lissencephaly 6, with microcephalyAR610
KIF11MicrocephalyAD3764
LIG4Severe combined immunodeficiency with sensitivity to ionizing radiation, LIG4 syndromeAR1635
MBD5Mental retardationAD4887
MCPH1MicrocephalyAR2232
MFSD2AMicrocephaly 15, primary, autosomal recessiveAR34
MRE11AAtaxia-telangiectasia-like disorder-1AR5751
MYCNFeingold syndromeAD2540
NDE1Microhydranencephaly, LissencephalyAR1215
NHEJ1Severe combined immunodeficiency with microcephaly, growth retardation, and sensitivity to ionizing radiationAR1415
OPHN1Mental retardation, with cerebellar hypoplasia and distinctive facial appearanceXL2536
PAFAH1B1Lissencephaly, Subcortical laminar heterotopiaAD118168
PCNTMicrocephalic osteodysplastic primordial dwarfismAR4884
PHGDHNeu-Laxova syndrome 1AR1519
PLK4Microcephaly and chorioretinopathy, autosomal recessive 2AR36
PNKPEpileptic encephalopathy, early infantile, Ataxia-oculomotorAR3417
POMT1Muscular dystrophy-dystroglycanopathyAR4194
PQBP1Renpenning syndromeXL1318
RARS2Pontocerebellar hypoplasiaAR2333
RTTNMicrocephaly, short stature, and polymicrogyria with or without seizuresAR1310
SEPSECSPontocerebellar hypoplasia, type 2DAR1014
STAMBPMicrocephaly-capillary malformation syndromeAR1419
STILMicrocephalyAR1114
TSEN2Pontocerebellar hypoplasiaAR84
TSEN54Pontocerebellar hypoplasiaAR2121
TUBB2BPolymicrogyria, asymmetricAD2030
TUBGCP4Microcephaly and chorioretinopathy, autosomal recessive 3AR75
TUBGCP6Microcephaly and chorioretinopathy, autosomal recessive 1AR156
VRK1Pontocerebellar hypoplasiaAR69
WDR62MicrocephalyAR3346
WDR73Galloway-Mowat syndromeAR912
XRCC4Short stature, microcephaly, and endocrine dysfunctionAR911

Non-coding variants covered by the panel

Gene Genomic location HG19 HGVS RefSeq RS-number
ASPMChr1:197097820c.2761-25A>GNM_018136.4rs199422149
CDK5RAP2Chr9:123182253c.4005-15A>GNM_018249.5rs387906274
EXOSC3Chr9:37782146c.475-12A>GNM_016042.3rs370087266
PNKPChr19:50364799c.1387-33_1386+49delCCTCCTCCCCTGACCCCNM_007254.3rs752902474
POMT1Chr9:134379574c.-30-2A>GNM_007171.3
RARS2Chr6:88244587c.613-3927C>TNM_020320.3
STAMBPChr2:74077998c.1005+358A>GNM_006463.4
XRCC4Chr5:82400728c.-10-1G>TNM_022406.2rs869320678

Panel Update

Genes added

  • AMPD2
  • GFM1
  • KANSL1
  • KATNB1
  • MFSD2A
  • MYCN
  • PHGDH
  • PLK4
  • RTTN
  • SEPSECS
  • STAMBP
  • TUBGCP4
  • TUBGCP6
  • WDR73
  • XRCC4

Genes removed

  • CEP164

Test strength and Limitations

The strengths of this test include:

  • CAP and ISO-15189 accreditations covering all operations at GHC Genetics including all Whole Exome Sequencing, NGS panels and confirmatory testing
  • CLIA-certified personnel performing clinical testing in a CLIA-certified laboratory
  • Powerful sequencing technologies, advanced target enrichment methods and precision bioinformatics pipelines ensure superior analytical performance
  • Careful construction of clinically effective and scientifically justified gene panels
  • Our Nucleus online portal providing transparent and easy access to quality and performance data at the patient level
  • Our publically available analytic validation demonstrating complete details of test performance
  • ~1,500 non-coding disease causing variants in GHC WES assay (please see below ‘Non-coding disease causing variants covered by this panel’)
  • Our rigorous variant classification based on modified ACMG variant classification scheme
  • Our systematic clinical interpretation workflow using proprietary software enabling accurate and traceable processing of NGS data
  • Our comprehensive clinical statements

Test limitations The following exons are not included in the panel as they are not sufficiently covered with high quality sequence reads: *PPA2* (11, 12). Genes with partial, or whole gene, segmental duplications in the human genome are marked with an asterisk if they overlap with the UCSC pseudogene regions. The technology may have limited sensitivity to detect variants in genes marked with these symbols (please see the Panel content table above).

This test does not detect the following:
  • Complex inversions
  • Gene conversions
  • Balanced translocations
  • Mitochondrial DNA variants
  • Repeat expansion disorders unless specifically mentioned
  • Non-coding variants deeper than ±20 base pairs from exon-intron boundary unless otherwise indicated (please see above Panel Content / non-coding variants covered by the panel).

This test may not reliably detect the following:
  • Low level mosaicism
  • Stretches of mononucleotide repeats
  • Indels larger than 50bp
  • Single exon deletions or duplications
  • Variants within pseudogene regions/duplicated segments

The sensitivity of this test may be reduced if DNA is extracted by a laboratory other than GHC Genetics.

For additional information, please refer to the Test performance section and see our Analytic Validation.

Test Performance

The GHC Genetics panel covers classical genes associated with Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), cardiac arrest underlying cardiac condition, cardiac arrest cause unspecified, syncope and collapse, abnormal ECG, Long QT syndrome, arrhythmogenic right ventricular cardiomyopathy (ARVC) and Short QT syndrome. The genes on the panel have been carefully selected based on scientific literature, mutation databases and our experience.

Our panels are sliced from our high-quality whole exome sequencing data. Please see our sequencing and detection performance table for different types of alterations at the whole exome level (Table).

Assays have been validated for different starting materials including EDTA-blood, isolated DNA (no FFPE), saliva and dry blood spots (filter card) and all provide high-quality results. The diagnostic yield varies substantially depending on the assay used, referring healthcare professional, hospital and country. GHC Genetics’ Plus Analysis (Seq+Del/Dup) maximizes the chance to find a molecular genetic diagnosis for your patient although Sequence Analysis or Del/Dup Analysis may be a cost-effective first line test if your patient’s phenotype is suggestive of a specific mutation type.

Performance of GHC Genetics Whole Exome Sequencing (WES) assay.
All individual panels are sliced from WES data.

Sensitivity % (TP/(TP+FN) Specificity %
Single nucleotide variants 99.65% (412,456/413,893) >99.99%
Insertions, deletions and indels by sequence analysis
1-10 bps 96.94% (17,070/17,608) >99.99%
11-50 bps 99.07% (957/966) >99.99%
Copy number variants (exon level dels/dups)
Clinical samples (small CNVs, n=52)
1 exon level deletion 92.3% (24/26) NA
2 exons level deletion/duplication 100.0% (11/11) NA
3-7 exons level deletion/duplication 93.3% (14/15) NA
Microdeletion/-duplication sdrs (large CNVs, n=37))
Size range (0.1-47 Mb) 100% (37/37)
Simulated CNV detection
2 exons level deletion/duplication 90.98% (7,357/8,086) 99.96%
5 exons level deletion/duplication 98.63% (7,975/8,086) 99.98%
The performance presented above reached by WES with the following coverage metrics
Mean sequencing depth at exome level 174x
Nucleotides with >20x sequencing coverage (%) 99.4%

Our mission is to improve the quality of the sequencing process and each modification is followed by our standardized validation process. Detection of Del/Dup of several genes is by MLPA analysis (MS Holland). All genes are performed by CNV analysis through the genome depending on exon size, sequencing coverage and sequence content. We have validated the assays for different starting materials including isolated DNA from EDTA blood that provide high-quality results.

Bioinformatics & clinical interpretation

The sequencing data generated in our laboratory is analysed by our bioinformatic pipeline, integrating state-of-the art algorithms and industry-standard software solutions. We use also JSI medical systems software for sequencing data analysis. JSI medical systems is a certified system offering sophisticated bioinformatic software solutions covering a wide field of sequencing techniques.

Incorporation of rigorous quality control steps throughout the workflow of the pipeline ensures the consistency, validity and accuracy of results.

Every pathogenic or probably pathogenic variant is confirmed by the Sanger sequencing method. Sanger sequencing is also used occasionally with other variants reported in the statement. In the case of variant of uncertain significance (VUS) we do not recommend risk stratification based on the genetic finding. The analysis of detected variants was performed on the basis of the reference database of polymorphisms and international mutation databases: UMD, LOVD and ClinVar.

The consequence of variants in coding and splice regions are estimated using Alamut software. The Alamut database contains more than 28000 coding genes, non-protein coding genes and pseudogenes. This database (shared with the high throughput annotation engine for NGS data, Alamut Batch) is frequently updated. Information comes from different public databases such as NCBI, EBI, and UCSC, as well as other sources including gnomAD, ESP, Cosmic, ClinVar, or HGMD and CentoMD (for those a separate subscription from Qiagen/Biobase and Centogene respectively is required). Alamut Visual finds information about nucleotide conservation data through many vertebrates’ species, with the phastCons and phyloP scores, amino acid conservation data through orthologue alignments and information on protein domains.

Moreover, we integrate several missense variant pathogenicity prediction tools and algorithms such as SIFT, PolyPhen, AlignGVGD or MutationTaster. It also offers a window dedicated to the in silico study of variants’ effect on RNA splicing, allowing the assessment of their potential impact on splice junctions and visualization of cryptic or de novo splice sites. Impact on splicing regulation is also assessed.


Clinical interpretation

At GHC Genetics our geneticists and clinicians, who together evaluate the results from the sequence analysis pipeline in the context of phenotype information provided in the requisition form, prepare the clinical report. We recommend an interpretation of the findings of this molecular genetic analysis, including subsequent oncological consultation for the patient in the context of genetic counselling for the patient.

We strive to continuously monitor current genetic literature identifying new relevant information and findings and adapting them to our diagnostics. This enables relevant novel discoveries to be rapidly translated and adopted into our ongoing diagnostics development without delay. The undertaking of such comprehensive due diligence ensures that our diagnostic panels and clinical statements are the most up-to-date on the market.

Variant classification is the corner stone of clinical interpretation and resulting patient management decisions. Minor modifications were made to increase reproducibility of the variant classification and improve the clinical validity of the report. Our experience with tens of thousands of clinical cases analysed at our laboratories enables us to further develop the industry standard.

The final step in the analysis of sequence variants is confirmation of variants classified as pathogenic or likely pathogenic using bi-directional Sanger sequencing. Variant(s) fulfilling all of the following criteria are not Sanger confirmed: 1) the variant quality score is above the internal threshold for a true positive call, 2) an unambiguous IGV in-line with the variant call and 3) previous Sanger confirmation of the same variant three times at GHC Genetics. Reported variants of uncertain significance (VUS) are confirmed with bi-directional Sanger sequencing only if the quality score is below our internally defined quality score for true positive call. Reported copy number variations with a size >10 exons are confirmed by orthogonal methods such as qPCR if the specific CNV has been seen less than three times at GHC Genetics.

Our clinical statement includes tables for sequencing and copy number variants that include basic variant information (genomic coordinates, HGVS nomenclature, zygosity, allele frequencies, in silico predictions, OMIM phenotypes and classification of the variant). In addition, the statement includes detailed descriptions of the variant, gene and phenotype(s) including the role of the specific gene in human disease, the mutation profile, information about the gene’s variation in population cohorts and detailed information about related phenotypes. We also provide links to the references used, and mutation databases to help our customers further evaluate the reported findings if desired. The conclusion summarizes all of the existing information and provides our rationale for the classification of the variant.

Identification of pathogenic or likely pathogenic variants in dominant disorders or their combinations in different alleles in recessive disorders are considered molecular confirmation of the clinical diagnosis. In these cases, family member testing can be used for risk stratification within the family. In the case of variants of uncertain significance (VUS), we do not recommend family member risk stratification based on the VUS result. Furthermore, in the case of VUS, we do not recommend the use of genetic information in patient management or genetic counselling.

Our Clinical interpretation team analyses millions of variants from thousands of individuals with rare diseases. Thus, our database, and our understanding of variants and related phenotypes, is growing by leaps and bounds. Our laboratories are therefore well positioned to re-classify previously reported variants as new information becomes available. If a variant previously reported by GHC Genetics is re-classified, our laboratories will issue a follow-up statement to the original ordering health care provider at no additional cost.

Microcephaly and Pontocerebellar Hypoplasia Panel

48 gene panel that includes assessment of non-coding variants

Ideal for patients with a clinical suspicion of microcephaly or pontocerebellar hypoplasias.

Analysis methods Availability Number of genes Test code CPT codes
PLUS
SEQ
DEL/DUP
4 weeks 48 GHC0217 SEQ 81405
SEQ 81406
SEQ 81407
DEL/DUP 81479

Summary

ICD codes
Commonly used ICD-10 code(s) when ordering the Microcephaly and Pontocerebellar Hypoplasia Panel

ICD-10 Disease
Q02 Microcephaly
Q04.3 Pontocerebellar hypoplasias

Sample requirements:

  • EDTA blood, min. 1 ml
  • Purified DNA, min. 3μg
  • Saliva (Oragene DNA OG-500 kit)

Label the sample tube with your patient’s name, date of birth and the date of sample collection. Note that we do not accept DNA samples isolated from formalin-fixed paraffin-embedded (FFPE) tissue.

About

Microcephaly is a neurodevelopmental disorder. It is usually defined as a head circumference (HC) more than two (or three) standard deviations below the mean for age and sex and serves as an important neurological indication or warning sign, however uniformity in its definition is lacking. Microcephaly may be congenital or develop in the first few years of life. In general, life expectancy for individuals with microcephaly is reduced and the prognosis for normal brain function is poor. It may stem from a wide variety of conditions that cause abnormal growth of the brain, or from syndromes associated with chromosomal abnormalities. A homozygous mutation in one of the microcephalin genes (MCPH1, ASPM, WDR62) causes primary microcephaly. Najm type X-linked intellectual deficit (point mutations and deletions in the CASK gene) is a rare cerebellar dysgenesis syndrome associated with microcephaly in most cases. Examples of monogenic syndromes associated with microcephaly are Seckel syndrome spectrum disorders. Nonsyndromic pontocerebellar hypoplasias (PCH) are a rare heterogeneous group of diseases characterized by hypoplasia and atrophy and/or early neurodegeneration of the cerebellum and pons. PCH patients of all subtypes present with progressive microencephaly, delayed or absence of cognitive and voluntary motor development, intellectual deficit, spasticity, chorea/dyskinesia, swallowing difficulties and seizures. The majority of PCH cases are caused by mutations in tRNA splicing endonuclease (TSEN genes). Approximately half the cases of PCH subtype 1 are due to mutations in the EXOSC3 gene. Other subtypes include mutations in for example TSEN2 and TSEN54 genes. Diagnosis is made based on clinical symptoms and neuroradiological findings (MRI) and can be confirmed by molecular genetic analyses. Nonsyndromic pontocerebellar hypoplasias (PCH) are generally inherited in an autosomal recessive pattern. Isolated microcephaly is known to have autosomal dominant, autosomal recessive and X-linked inheritance.

Panel Content

Genes in the Microcephaly and Pontocerebellar Hypoplasia Panel and their clinical significance

Gene Associated phenotypes Inheritance ClinVar HGMD
AKT3Megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndromeAD1227
AMPD2Pontocerebellar hypoplasia type 9, Spastic paraplegia 63AR1415
ASPMMicrocephalyAR171174
ATRCutaneous telangiectasia and cancer syndrome, Seckel syndromeAD/AR818
CASKMental retardation and microcephaly with pontine and cerebellar hypoplasia, FG syndrome, Mental retardationXL80104
CDK5RAP2MicrocephalyAR1920
CENPFCiliary dyskinesia -Lethal CiliopathyAR127
CENPJSeckel syndrome, MicrocephalyAR329
CEP63Seckel syndromeAR72
CEP152Seckel syndrome, MicrocephalyAR1920
DYNC1H1Spinal muscular atrophy, Charcot-Marie-Tooth disease, Mental retardationAD5764
DYRK1AMental retardationAD8777
EFTUD2Mandibulofacial dysostosis with microcephaly, Esophageal atresia, syndromicAD4393
EXOSC3Pontocerebellar hypoplasiaAR1219
GFM1Combined oxidative phosphorylation deficiencyAR1818
KANSL1Koolen-de Vries syndromeAD5463
KATNB1Lissencephaly 6, with microcephalyAR610
KIF11MicrocephalyAD3764
LIG4Severe combined immunodeficiency with sensitivity to ionizing radiation, LIG4 syndromeAR1635
MBD5Mental retardationAD4887
MCPH1MicrocephalyAR2232
MFSD2AMicrocephaly 15, primary, autosomal recessiveAR34
MRE11AAtaxia-telangiectasia-like disorder-1AR5751
MYCNFeingold syndromeAD2540
NDE1Microhydranencephaly, LissencephalyAR1215
NHEJ1Severe combined immunodeficiency with microcephaly, growth retardation, and sensitivity to ionizing radiationAR1415
OPHN1Mental retardation, with cerebellar hypoplasia and distinctive facial appearanceXL2536
PAFAH1B1Lissencephaly, Subcortical laminar heterotopiaAD118168
PCNTMicrocephalic osteodysplastic primordial dwarfismAR4884
PHGDHNeu-Laxova syndrome 1AR1519
PLK4Microcephaly and chorioretinopathy, autosomal recessive 2AR36
PNKPEpileptic encephalopathy, early infantile, Ataxia-oculomotorAR3417
POMT1Muscular dystrophy-dystroglycanopathyAR4194
PQBP1Renpenning syndromeXL1318
RARS2Pontocerebellar hypoplasiaAR2333
RTTNMicrocephaly, short stature, and polymicrogyria with or without seizuresAR1310
SEPSECSPontocerebellar hypoplasia, type 2DAR1014
STAMBPMicrocephaly-capillary malformation syndromeAR1419
STILMicrocephalyAR1114
TSEN2Pontocerebellar hypoplasiaAR84
TSEN54Pontocerebellar hypoplasiaAR2121
TUBB2BPolymicrogyria, asymmetricAD2030
TUBGCP4Microcephaly and chorioretinopathy, autosomal recessive 3AR75
TUBGCP6Microcephaly and chorioretinopathy, autosomal recessive 1AR156
VRK1Pontocerebellar hypoplasiaAR69
WDR62MicrocephalyAR3346
WDR73Galloway-Mowat syndromeAR912
XRCC4Short stature, microcephaly, and endocrine dysfunctionAR911

Non-coding variants covered by the panel

Gene Genomic location HG19 HGVS RefSeq RS-number
ASPMChr1:197097820c.2761-25A>GNM_018136.4rs199422149
CDK5RAP2Chr9:123182253c.4005-15A>GNM_018249.5rs387906274
EXOSC3Chr9:37782146c.475-12A>GNM_016042.3rs370087266
PNKPChr19:50364799c.1387-33_1386+49delCCTCCTCCCCTGACCCCNM_007254.3rs752902474
POMT1Chr9:134379574c.-30-2A>GNM_007171.3
RARS2Chr6:88244587c.613-3927C>TNM_020320.3
STAMBPChr2:74077998c.1005+358A>GNM_006463.4
XRCC4Chr5:82400728c.-10-1G>TNM_022406.2rs869320678

Panel Update

Genes added

  • AMPD2
  • GFM1
  • KANSL1
  • KATNB1
  • MFSD2A
  • MYCN
  • PHGDH
  • PLK4
  • RTTN
  • SEPSECS
  • STAMBP
  • TUBGCP4
  • TUBGCP6
  • WDR73
  • XRCC4

Genes removed

  • CEP164

Test strength and Limitations

The strengths of this test include:

  • CAP and ISO-15189 accreditations covering all operations at GHC Genetics including all Whole Exome Sequencing, NGS panels and confirmatory testing
  • CLIA-certified personnel performing clinical testing in a CLIA-certified laboratory
  • Powerful sequencing technologies, advanced target enrichment methods and precision bioinformatics pipelines ensure superior analytical performance
  • Careful construction of clinically effective and scientifically justified gene panels
  • Our Nucleus online portal providing transparent and easy access to quality and performance data at the patient level
  • Our publically available analytic validation demonstrating complete details of test performance
  • ~1,500 non-coding disease causing variants in GHC WES assay (please see below ‘Non-coding disease causing variants covered by this panel’)
  • Our rigorous variant classification based on modified ACMG variant classification scheme
  • Our systematic clinical interpretation workflow using proprietary software enabling accurate and traceable processing of NGS data
  • Our comprehensive clinical statements

Test limitations The following exons are not included in the panel as they are not sufficiently covered with high quality sequence reads: *PPA2* (11, 12). Genes with partial, or whole gene, segmental duplications in the human genome are marked with an asterisk if they overlap with the UCSC pseudogene regions. The technology may have limited sensitivity to detect variants in genes marked with these symbols (please see the Panel content table above).

This test does not detect the following:
  • Complex inversions
  • Gene conversions
  • Balanced translocations
  • Mitochondrial DNA variants
  • Repeat expansion disorders unless specifically mentioned
  • Non-coding variants deeper than ±20 base pairs from exon-intron boundary unless otherwise indicated (please see above Panel Content / non-coding variants covered by the panel).

This test may not reliably detect the following:
  • Low level mosaicism
  • Stretches of mononucleotide repeats
  • Indels larger than 50bp
  • Single exon deletions or duplications
  • Variants within pseudogene regions/duplicated segments

The sensitivity of this test may be reduced if DNA is extracted by a laboratory other than GHC Genetics.

For additional information, please refer to the Test performance section and see our Analytic Validation.

Test Performance

The GHC Genetics panel covers classical genes associated with Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia (CPVT), cardiac arrest underlying cardiac condition, cardiac arrest cause unspecified, syncope and collapse, abnormal ECG, Long QT syndrome, arrhythmogenic right ventricular cardiomyopathy (ARVC) and Short QT syndrome. The genes on the panel have been carefully selected based on scientific literature, mutation databases and our experience.

Our panels are sliced from our high-quality whole exome sequencing data. Please see our sequencing and detection performance table for different types of alterations at the whole exome level (Table).

Assays have been validated for different starting materials including EDTA-blood, isolated DNA (no FFPE), saliva and dry blood spots (filter card) and all provide high-quality results. The diagnostic yield varies substantially depending on the assay used, referring healthcare professional, hospital and country. GHC Genetics’ Plus Analysis (Seq+Del/Dup) maximizes the chance to find a molecular genetic diagnosis for your patient although Sequence Analysis or Del/Dup Analysis may be a cost-effective first line test if your patient’s phenotype is suggestive of a specific mutation type.

Performance of GHC Genetics Whole Exome Sequencing (WES) assay.
All individual panels are sliced from WES data.

Sensitivity % (TP/(TP+FN) Specificity %
Single nucleotide variants 99.65% (412,456/413,893) >99.99%
Insertions, deletions and indels by sequence analysis
1-10 bps 96.94% (17,070/17,608) >99.99%
11-50 bps 99.07% (957/966) >99.99%
Copy number variants (exon level dels/dups)
Clinical samples (small CNVs, n=52)
1 exon level deletion 92.3% (24/26) NA
2 exons level deletion/duplication 100.0% (11/11) NA
3-7 exons level deletion/duplication 93.3% (14/15) NA
Microdeletion/-duplication sdrs (large CNVs, n=37))
Size range (0.1-47 Mb) 100% (37/37)
Simulated CNV detection
2 exons level deletion/duplication 90.98% (7,357/8,086) 99.96%
5 exons level deletion/duplication 98.63% (7,975/8,086) 99.98%
The performance presented above reached by WES with the following coverage metrics
Mean sequencing depth at exome level 174x
Nucleotides with >20x sequencing coverage (%) 99.4%

Our mission is to improve the quality of the sequencing process and each modification is followed by our standardized validation process. Detection of Del/Dup of several genes is by MLPA analysis (MS Holland). All genes are performed by CNV analysis through the genome depending on exon size, sequencing coverage and sequence content. We have validated the assays for different starting materials including isolated DNA from EDTA blood that provide high-quality results.

Bioinformatics & clinical interpretation

The sequencing data generated in our laboratory is analysed by our bioinformatic pipeline, integrating state-of-the art algorithms and industry-standard software solutions. We use also JSI medical systems software for sequencing data analysis. JSI medical systems is a certified system offering sophisticated bioinformatic software solutions covering a wide field of sequencing techniques.

Incorporation of rigorous quality control steps throughout the workflow of the pipeline ensures the consistency, validity and accuracy of results.

Every pathogenic or probably pathogenic variant is confirmed by the Sanger sequencing method. Sanger sequencing is also used occasionally with other variants reported in the statement. In the case of variant of uncertain significance (VUS) we do not recommend risk stratification based on the genetic finding. The analysis of detected variants was performed on the basis of the reference database of polymorphisms and international mutation databases: UMD, LOVD and ClinVar.

The consequence of variants in coding and splice regions are estimated using Alamut software. The Alamut database contains more than 28000 coding genes, non-protein coding genes and pseudogenes. This database (shared with the high throughput annotation engine for NGS data, Alamut Batch) is frequently updated. Information comes from different public databases such as NCBI, EBI, and UCSC, as well as other sources including gnomAD, ESP, Cosmic, ClinVar, or HGMD and CentoMD (for those a separate subscription from Qiagen/Biobase and Centogene respectively is required). Alamut Visual finds information about nucleotide conservation data through many vertebrates’ species, with the phastCons and phyloP scores, amino acid conservation data through orthologue alignments and information on protein domains.

Moreover, we integrate several missense variant pathogenicity prediction tools and algorithms such as SIFT, PolyPhen, AlignGVGD or MutationTaster. It also offers a window dedicated to the in silico study of variants’ effect on RNA splicing, allowing the assessment of their potential impact on splice junctions and visualization of cryptic or de novo splice sites. Impact on splicing regulation is also assessed.


Clinical interpretation

At GHC Genetics our geneticists and clinicians, who together evaluate the results from the sequence analysis pipeline in the context of phenotype information provided in the requisition form, prepare the clinical report. We recommend an interpretation of the findings of this molecular genetic analysis, including subsequent oncological consultation for the patient in the context of genetic counselling for the patient.

We strive to continuously monitor current genetic literature identifying new relevant information and findings and adapting them to our diagnostics. This enables relevant novel discoveries to be rapidly translated and adopted into our ongoing diagnostics development without delay. The undertaking of such comprehensive due diligence ensures that our diagnostic panels and clinical statements are the most up-to-date on the market.

Variant classification is the corner stone of clinical interpretation and resulting patient management decisions. Minor modifications were made to increase reproducibility of the variant classification and improve the clinical validity of the report. Our experience with tens of thousands of clinical cases analysed at our laboratories enables us to further develop the industry standard.

The final step in the analysis of sequence variants is confirmation of variants classified as pathogenic or likely pathogenic using bi-directional Sanger sequencing. Variant(s) fulfilling all of the following criteria are not Sanger confirmed: 1) the variant quality score is above the internal threshold for a true positive call, 2) an unambiguous IGV in-line with the variant call and 3) previous Sanger confirmation of the same variant three times at GHC Genetics. Reported variants of uncertain significance (VUS) are confirmed with bi-directional Sanger sequencing only if the quality score is below our internally defined quality score for true positive call. Reported copy number variations with a size >10 exons are confirmed by orthogonal methods such as qPCR if the specific CNV has been seen less than three times at GHC Genetics.

Our clinical statement includes tables for sequencing and copy number variants that include basic variant information (genomic coordinates, HGVS nomenclature, zygosity, allele frequencies, in silico predictions, OMIM phenotypes and classification of the variant). In addition, the statement includes detailed descriptions of the variant, gene and phenotype(s) including the role of the specific gene in human disease, the mutation profile, information about the gene’s variation in population cohorts and detailed information about related phenotypes. We also provide links to the references used, and mutation databases to help our customers further evaluate the reported findings if desired. The conclusion summarizes all of the existing information and provides our rationale for the classification of the variant.

Identification of pathogenic or likely pathogenic variants in dominant disorders or their combinations in different alleles in recessive disorders are considered molecular confirmation of the clinical diagnosis. In these cases, family member testing can be used for risk stratification within the family. In the case of variants of uncertain significance (VUS), we do not recommend family member risk stratification based on the VUS result. Furthermore, in the case of VUS, we do not recommend the use of genetic information in patient management or genetic counselling.

Our Clinical interpretation team analyses millions of variants from thousands of individuals with rare diseases. Thus, our database, and our understanding of variants and related phenotypes, is growing by leaps and bounds. Our laboratories are therefore well positioned to re-classify previously reported variants as new information becomes available. If a variant previously reported by GHC Genetics is re-classified, our laboratories will issue a follow-up statement to the original ordering health care provider at no additional cost.