Cone Rod Dystrophy Panel

Summary
Is a 44 gene panel that includes assessment of non-coding variants.

Is ideal for patients with a clinical suspicion / diagnosis of cone rod dystrophy. The genes on this panel are included in the Retinal Dystrophy Panel.

Analysis methods
  • PLUS
Availability
4 weeks
Number of genes
44
Test code
OP0401
Panel tier
Tier 2
CPT Code *
81408, 81406 x2, 81404 x2, 81479
* The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

Summary

The Blueprint Genetics Cone Rod Dystrophy Panel (test code OP0401):

Read about our accreditations, certifications and CE-marked IVD medical devices here.

The majority of the X-linked RP is caused by mutations in the*RPGR* gene, which contains a mutational hotspot at a unique 567-aa exon called ORF15 accounting for two-thirds of all disease-causing mutations. The exon ORF15, however, includes a highly repetitive, purine-rich sequence, which generally performs poorly in NGS-based assays. Blueprint Genetics custom assay has good coverage (>20x) with high mapping rates (mapping quality >20) for 100.0% of the target regions in *RPGR* gene. Our validation showed high mean coverage of 139X for the *RPGR* gene. Thus, our NGS Panel is not expected to have major limitations in detecting variants in *RPGR* gene including ORF15 exon.

ICD Codes

Refer to the most current version of ICD-10-CM manual for a complete list of ICD-10 codes.

Sample Requirements

  • Blood (min. 1ml) in an EDTA tube
  • Extracted DNA, min. 2 μg in TE buffer or equivalent
  • Saliva (Please see Sample Requirements for accepted saliva kits)

Label the sample tube with your patient’s name, date of birth and the date of sample collection.

We do not accept DNA samples isolated from formalin-fixed paraffin-embedded (FFPE) tissue. In addition, if the patient is affected with a hematological malignancy, DNA extracted from a non-hematological source (e.g. skin fibroblasts) is strongly recommended.

Please note that, in rare cases, mitochondrial genome (mtDNA) variants may not be detectable in blood or saliva in which case DNA extracted from post-mitotic tissue such as skeletal muscle may be a better option.

Read more about our sample requirements here.

Please include fundus photographs, electroretinogram (ERG) findings, visual field findings and visual acuity, if available, for expert review and clinical correlation with test results

Cone rod dystrophies (CRD) are inherited retinal dystrophies characterized by cone dysfunction followed by rod photoreceptor degeneration. Fundus examination shows pigment deposits and retinal atrophy in the macular region of the retina. In contrast to typical retinitis pigmentosa (RP, rod cone dystrophy) resulting from the primary loss of rod photoreceptors and later followed by the secondary loss of cone photoreceptors, CRDs reflect the opposite sequence of events. Predominant symptoms of CRDs are decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RP, leading to earlier legal blindness and disability. CRDs are most frequently nonsyndromic, but they may also be part of several syndromes, such as Bardet-Biedl syndrome. Nonsyndromic CRDs can be inherited in an autosomal dominant, autosomal recessive or X-linked manner. The two major causative genes involved in the pathogenesis of CRDs are ABCA4 (autosomal recessive CRD, also implicated in Stargardt disease) and GUCY2D (autosomal dominant CRD). The prevalence of CRDs is estimated at 1:40,000.

Genes in the Cone Rod Dystrophy Panel and their clinical significance

To view complete table content, scroll horizontally.

Gene Associated phenotypes Inheritance ClinVar HGMD
ABCA4 Stargardt disease, Retinitis pigmentosa, Cone rod dystrophy, Retinal dystrophy, early-onset severe, Fundus flavimaculatus AR 308 1231
ADAM9 Cone rod dystrophy AR 6 10
ADAMTS18 Knobloch syndrome 2, Microcornea, myopic chorioretinal atrophy, and telecanthus, Retinal dystrophy, early onset, autosomal recessive AR 4 14
AIPL1 Retinitis pigmentosa, Cone rod dystrophy, Leber congenital amaurosis AR 10 79
ARHGEF18 Retinitis pigmentosa 78 AR 5 6
BEST1 Vitreoretinochoroidopathy, Microcornea, Rod-cone dystrophy, Posterior staphyloma, Bestrophinopathy, Vitelliform macular dystrophy, Cataract, Retinitis pigmentosa, Macular dystrophy, vitelliform, adult-onset, Retinitis pigmentosa 50, Macular dystrophy, vitelliform 2, Best macular dystrophy, Bestrophinopathy, autosomal recessive AD/AR 62 318
C21ORF2 Retinal dystrophy with or without macular staphyloma (RDMS), Spondylometaphyseal dysplasia, axial (SMDAX) AR 13 22
C8ORF37 Retinitis pigmentosa, Cone rod dystrophy, Bardet-Biedl syndrome 21 AR 8 17
CABP4 Night blindness, congenital stationary AR 6 11
CACNA1F Aland Island eye disease, Cone rod dystrophy, Night blindness, congenital stationary XL 39 182
CACNA2D4 Retinal cone dystrophy AR 3 9
CDHR1 Retinitis pigmentosa, Cone rod dystrophy AR 12 48
CEP250 Cone rod dystrophy and hearing loss AR 5
CEP78 Cone rod dystrophy and hearing loss AR 7 9
CERKL Retinitis pigmentosa AR 20 37
CLN3 Neuronal ceroid lipofuscinosis, type 3 AR 100 72
CNGA3 Leber congenital amaurosis, Achromatopsia AR 32 149
CNGB3 Macular degeneration, juvenile, Achromatopsia AR 115 124
CNNM4 Jalili syndrome AR 11 24
CRB1 Retinitis pigmentosa, Pigmented paravenous chorioretinal atrophy, Leber congenital amaurosis AR 54 334
CRX Cone rod dystrophy, Leber congenital amaurosis AD/AR 30 106
CYP4V2 Retinitis pigmentosa, Bietti crystalline corneoretinal dystrophy AR 31 94
ELOVL4 Stargardt disease, Icthyosis, spastic quadriplegia, and mental retardation, Spinocerebellar ataxia AD/AR 13 14
GNAT2 Achromatopsia AR 7 16
GUCA1A Cone dystrophy 3/Cone rod dystrophy AD 7 21
GUCY2D Cone rod dystrophy, Leber congenital amaurosis AD/AR 34 235
KCNV2 Retinal cone dystrophy AR 16 94
MERTK Retinitis pigmentosa AR 25 75
PDE6C Cone dystrophy AR 31 44
PDE6H Retinal cone dystrophy, Achromatopsia AR 2 2
PITPNM3 Cone-rod dystrophy 5 AD 1 5
POC1B Cone-rod dystrophy 20 AR 4 7
PROM1 Stargardt disease, Retinitis pigmentosa, Cone rod dystrophy, Macular dystrophy, retinal, AD/AR 22 80
PRPH2 Choriodal dystrophy, central areolar, Macular dystrophy, vitelliform, Retinitis pigmentosa, Retinitis punctata albescens, Macula dystrophy, patterned AD/AR 48 176
RAB28 Cone-rod dystrophy 18 AR 4 5
RAX2 Cone rod dystrophy AD/AR 5 4
RDH5 Fundus albipunctatus AR 11 51
RGS9 Bradyopsia AR 2 2
RGS9BP Bradyopsia AR 2 7
RIMS1 Cone-rod dystrophy 7 AD 3 12
RPGR Retinitis pigmentosa, Cone-rod dystrophy, X-linked, 1, Macular degeneration, X-linked atrophic, Retinitis pigmentosa 3 XL 79 218
RPGRIP1 Cone rod dystrophy, Leber congenital amaurosis AR 44 145
SEMA4A Retinitis pigmentosa, Cone rod dystrophy AR 4 14
TTLL5 Cone-rod dystrophy 19 AR 13 12

Gene refers to the HGNC approved gene symbol; Inheritance refers to inheritance patterns such as autosomal dominant (AD), autosomal recessive (AR), mitochondrial (mi), X-linked (XL), X-linked dominant (XLD) and X-linked recessive (XLR); ClinVar refers to the number of variants in the gene classified as pathogenic or likely pathogenic in this database (ClinVar); HGMD refers to the number of variants with possible disease association in the gene listed in Human Gene Mutation Database (HGMD). The list of associated, gene specific phenotypes are generated from CGD or Mitomap databases.

Non-coding variants covered by Cone Rod Dystrophy Panel

To view complete table content, scroll horizontally.

Gene Genomic location HG19 HGVS RefSeq RS-number
ABCA4 Chr1:94461770 c.6730-19G>A NM_000350.2 rs375179475
ABCA4 Chr1:94468019 c.6148-471C>T NM_000350.2
ABCA4 Chr1:94481967 c.5197–557G>T NM_000350.2
ABCA4 Chr1:94484001 c.5196+1137G>A NM_000350.2 rs778234759
ABCA4 Chr1:94484001 c.5196+1137G>T NM_000350.2
ABCA4 Chr1:94484082 c.5196+1056A>G NM_000350.2
ABCA4 Chr1:94492936 c.4539+2065C>G NM_000350.2
ABCA4 Chr1:94492937 c.4539+2064C>T NM_000350.2
ABCA4 Chr1:94492973 c.4539+2028C>T NM_000350.2 rs869320785
ABCA4 Chr1:94493000 c.4539+2001G>A NM_000350.2
ABCA4 Chr1:94493073 c.4539+1928C>T NM_000350.2
ABCA4 Chr1:94493272 c.4539+1729G>T NM_000350.2
ABCA4 Chr1:94493895 c.4539 +1106C>T NM_000350.2
ABCA4 Chr1:94493901 c.4539+1100A>G NM_000350.2
ABCA4 Chr1:94496509 c.4253+43G>A NM_000350.2
ABCA4 Chr1:94508465 c.3191–11T>A NM_000350.2
ABCA4 Chr1:94509047 c.3051-16T>A NM_000350.2
ABCA4 Chr1:94509799 c.3050+370C>T NM_000350.2
ABCA4 Chr1:94510683 c.2919-383C>T NM_000350.2
ABCA4 Chr1:94525509 c.2160+584A>G NM_000350.2
ABCA4 Chr1:94526934 c.1938-619A>G NM_000350.2
ABCA4 Chr1:94527698 c.1937+435C>G NM_000350.2
ABCA4 Chr1:94528120 c.1937+13T>G NM_000350.2
ABCA4 Chr1:94546780 c.859-506G>C NM_000350.2
ABCA4 Chr1:94546814 c.859–540C>G NM_000350.2
ABCA4 Chr1:94549781 c.769–784C>T NM_000350.2
ABCA4 Chr1:94561127 c.768+3223C>T NM_000350.2
ABCA4 Chr1:94566773 c.570+1798A>G NM_000350.2
ABCA4 Chr1:94576926 c.302+68C>T NM_000350.2 rs761188244
ABCA4 Chr1:94577158 c.161–23T>G NM_000350.2
ABCA4 Chr1:94578638 c.67-16T>A NM_000350.2
BEST1 Chr11:61717900 c.-29+1G>T NM_001139443.1
BEST1 Chr11:61717904 c.-29+5G>A NM_001139443.1
C21ORF2 Chr21:45750232 c.1000-23A>T NM_001271441.1
CLN3 Chr16:28493392 c.1056+34C>A NM_000086.2
CLN3 Chr16:28497984 c.461-13G>C NM_000086.2 rs386833721
CNGA3 Chr2:98986401 c.-37-1G>C NM_001298.2
GNAT2 Chr1:110151229 c.461+24G>A NM_005272.3 rs397515384
GUCY2D Chr17:7906220 c.-9-137T>C NM_000180.3
PDE6C Chr10:95380377 c.481-12T>A NM_006204.3 rs786200909
PROM1 Chr4:15989860 c.2077-521A>G NM_006017.2 rs796051882
RDH5 Chr12:56114302 c.-33+2dupT NM_002905.3
RPGR ChrX:38128234 NM_000328.2
RPGR ChrX:38160137 c.1059+363G>A NM_001034853.1
RPGRIP1 Chr14:21789155 c.1468-263G>C NM_020366.3
RPGRIP1 Chr14:21789588 c.1611+27G>A NM_020366.3
RPGRIP1 Chr14:21793563 c.2367+23delG NM_020366.3 rs781728563
RPGRIP1 Chr14:21793564 c.2367+23delG NM_020366.3
RPGRIP1 Chr14:21795769 c.2711-13G>T NM_020366.3 rs369991630

Test Strengths

The majority of the X-linked RP is caused by mutations in the*RPGR* gene, which contains a mutational hotspot at a unique 567-aa exon called ORF15 accounting for two-thirds of all disease-causing mutations. The exon ORF15, however, includes a highly repetitive, purine-rich sequence, which generally performs poorly in NGS-based assays. Blueprint Genetics custom assay has good coverage (>20x) with high mapping rates (mapping quality >20) for 100.0% of the target regions in *RPGR* gene. Our validation showed high mean coverage of 139X for the *RPGR* gene. Thus, our NGS Panel is not expected to have major limitations in detecting variants in *RPGR* gene including ORF15 exon.

The strengths of this test include:

  • CAP accredited laboratory
  • 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
  • Some of the panels include the whole mitochondrial genome (please see the Panel Content section)
  • Our Nucleus online portal providing transparent and easy access to quality and performance data at the patient level
  • ~2,000 non-coding disease causing variants in our clinical grade NGS assay for panels (please see ‘Non-coding disease causing variants covered by this panel’ in the Panel Content section)
  • Our rigorous 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

Genes with suboptimal coverage in our assay are marked with number sign (#). Gene is considered to have suboptimal coverage when >90% of the gene’s target nucleotides are not covered at >20x with mapping quality score (MQ>20) reads. 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
  • Some of the panels include the whole mitochondrial genome but not all (please see the Panel Content section)
  • 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 in nuclear genes (variant with a minor allele fraction of 14.6% is detected with 90% probability)
  • Stretches of mononucleotide repeats
  • Low level heteroplasmy in mtDNA (>90% are detected at 5% level)
  • Indels larger than 50bp
  • Single exon deletions or duplications
  • Variants within pseudogene regions/duplicated segments
  • Some disease causing variants present in mtDNA are not detectable from blood, thus post-mitotic tissue such as skeletal muscle may be required for establishing molecular diagnosis.

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

For additional information, please refer to the Test performance section.

The genes on the panel have been carefully selected based on scientific literature, mutation databases and our experience.

Our panels are sectioned from our high-quality, clinical grade NGS assay. Please see our sequencing and detection performance table for details regarding our ability to detect different types of alterations (Table).

Assays have been validated for various sample types including EDTA-blood, isolated DNA (excluding from formalin fixed paraffin embedded tissue), saliva and dry blood spots (filter cards). These sample types were selected in order to maximize the likelihood for high-quality DNA yield. The diagnostic yield varies depending on the assay used, referring healthcare professional, hospital and country. Plus analysis increases the likelihood of finding a genetic diagnosis for your patient, as large deletions and duplications cannot be detected using sequence analysis alone. Blueprint Genetics’ Plus Analysis is a combination of both sequencing and deletion/duplication (copy number variant (CNV)) analysis.

The performance metrics listed below are from an initial validation performed at our main laboratory in Finland. The performance metrics of our laboratory in Marlborough, MA, are equivalent.

Performance of Blueprint Genetics high-quality, clinical grade NGS sequencing assay for panels.

Sensitivity % (TP/(TP+FN) Specificity %
Single nucleotide variants 99.89% (99,153/99,266) >99.9999%
Insertions, deletions and indels by sequence analysis
1-10 bps 99.2% (7,745/7,806) >99.9999%
11-50 bps 99.13% (2,524/2,546) >99.9999%
Copy number variants (exon level dels/dups)
1 exon level deletion (heterozygous) 100% (20/20) NA
1 exon level deletion (homozygous) 100% (5/5) NA
1 exon level deletion (het or homo) 100% (25/25) NA
2-7 exon level deletion (het or homo) 100% (44/44) NA
1-9 exon level duplication (het or homo) 75% (6/8) NA
Simulated CNV detection
5 exons level deletion/duplication 98.7% 100.00%
Microdeletion/-duplication sdrs (large CNVs, n=37))
Size range (0.1-47 Mb) 100% (25/25)
     
The performance presented above reached by Blueprint Genetics high-quality, clinical grade NGS sequencing assay with the following coverage metrics
     
Mean sequencing depth 143X
Nucleotides with >20x sequencing coverage (%) 99.86%

Performance of Blueprint Genetics Mitochondrial Sequencing Assay.

Sensitivity % Specificity %
ANALYTIC VALIDATION (NA samples; n=4)
Single nucleotide variants
Heteroplasmic (45-100%) 100.0% (50/50) 100.0%
Heteroplasmic (35-45%) 100.0% (87/87) 100.0%
Heteroplasmic (25-35%) 100.0% (73/73) 100.0%
Heteroplasmic (15-25%) 100.0% (77/77) 100.0%
Heteroplasmic (10-15%) 100.0% (74/74) 100.0%
Heteroplasmic (5-10%) 100.0% (3/3) 100.0%
Heteroplasmic (<5%) 50.0% (2/4) 100.0%
CLINICAL VALIDATION (n=76 samples)
All types
Single nucleotide variants n=2026 SNVs
Heteroplasmic (45-100%) 100.0% (1940/1940) 100.0%
Heteroplasmic (35-45%) 100.0% (4/4) 100.0%
Heteroplasmic (25-35%) 100.0% (3/3) 100.0%
Heteroplasmic (15-25%) 100.0% (3/3) 100.0%
Heteroplasmic (10-15%) 100.0% (9/9) 100.0%
Heteroplasmic (5-10%) 92.3% (12/13) 99.98%
Heteroplasmic (<5%) 88.9% (48/54) 99.93%
Insertions and deletions by sequence analysis n=40 indels
Heteroplasmic (45-100%) 1-10bp 100.0% (32/32) 100.0%
Heteroplasmic (5-45%) 1-10bp 100.0% (3/3) 100.0%
Heteroplasmic (<5%) 1-10bp 100.0% (5/5) 99,997%
SIMULATION DATA /(mitomap mutations)
Insertions, and deletions 1-24 bps by sequence analysis; n=17
Homoplasmic (100%) 1-24bp 100.0% (17/17) 99.98%
Heteroplasmic (50%) 100.0% (17/17) 99.99%
Heteroplasmic (25%) 100.0% (17/17) 100.0%
Heteroplasmic (20%) 100.0% (17/17) 100.0%
Heteroplasmic (15%) 100.0% (17/17) 100.0%
Heteroplasmic (10%) 94.1% (16/17) 100.0%
Heteroplasmic (5%) 94.1% (16/17) 100.0%
Copy number variants (separate artifical mutations; n=1500)
Homoplasmic (100%) 500 bp, 1kb, 5 kb 100.0% 100.0%
Heteroplasmic (50%) 500 bp, 1kb, 5 kb 100.0% 100.0%
Heteroplasmic (30%) 500 bp, 1kb, 5 kb 100.0% 100.0%
Heteroplasmic (20%) 500 bp, 1kb, 5 kb 99.7% 100.0%
Heteroplasmic (10%) 500 bp, 1kb, 5 kb 99.0% 100.0%
The performance presented above reached by following coverage metrics at assay level (n=66)
Mean of medians Median of medians
Mean sequencing depth MQ0 (clinical) 18224X 17366X
Nucleotides with >1000x MQ0 sequencing coverage (%) (clinical) 100%
rho zero cell line (=no mtDNA), mean sequencing depth 12X

The target region for each gene includes coding exons and ±20 base pairs from the exon-intron boundary. In addition, the panel includes non-coding and regulatory variants if listed above (Non-coding variants covered by the panel). Some regions of the gene(s) may be removed from the panel if specifically mentioned in the ‘Test limitations” section above. If the test includes the mitochondrial genome the target region gene list contains the mitochondrial genes. The sequencing data generated in our laboratory is analyzed with our proprietary data analysis and annotation pipeline, integrating state-of-the art algorithms and industry-standard software solutions. Incorporation of rigorous quality control steps throughout the workflow of the pipeline ensures the consistency, validity and accuracy of results. Our pipeline is streamlined to maximize sensitivity without sacrificing specificity. We have incorporated a number of reference population databases and mutation databases including, but not limited, to 1000 Genomes Project, gnomAD, ClinVar and HGMD into our clinical interpretation software to make the process effective and efficient. For missense variants, in silico variant prediction tools such as  SIFT, PolyPhen,MutationTaster are used to assist with variant classification. Through our online ordering and statement reporting system, Nucleus, ordering providers have access to the details of the analysis, including patient specific sequencing metrics, a gene level coverage plot and a list of regions with suboptimal coverage (<20X for nuclear genes and <1000X for mtDNA) if applicable. This reflects our mission to build fully transparent diagnostics where ordering providers can easily visualize the crucial details of the analysis process.

We provide customers with the most comprehensive clinical report available on the market. Clinical interpretation requires a fundamental understanding of clinical genetics and genetic principles. At Blueprint Genetics, our PhD molecular geneticists, medical geneticists, and clinical consultants prepare the clinical statement together by evaluating the identified variants in the context of the phenotypic information provided in the requisition form. Our goal is to provide clinically meaningful statements that are understandable for all medical professionals regardless of whether they have formal training in genetics.

Variant classification is the cornerstone of clinical interpretation and resulting patient management decisions. Our classifications follow the ACMG guideline 2015.

The final step in the analysis is orthogonal confirmation. Sequence and copy number variants classified as pathogenic, likely pathogenic, and variants of uncertain significance (VUS) are confirmed using bi-directional Sanger sequencing or by orthogonal methods such as qPCR/ddPCR when they do not meet our stringent NGS quality metrics for a true positive call.

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, abstracts, and variant databases used to help ordering providers 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. We do not recommend using variants of uncertain significance (VUS) for family member risk stratification or patient management. Genetic counseling is recommended.

Our interpretation team analyzes millions of variants from thousands of individuals with rare diseases. Our internal database and our understanding of variants and related phenotypes increases with every case analyzed. Our laboratory is therefore well-positioned to re-classify previously reported variants as new information becomes available. If a variant previously reported by Blueprint Genetics is re-classified, our laboratory will issue a follow-up statement to the original ordering healthcare provider at no additional cost, according to our latest follow-up reporting policy.