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Chromosomal microarray technologies, including array comparative genomic hybridization and single-nucleotide polymorphism array, are widely applied in the diagnostic evaluation for both constitutional and neoplastic disorders. In a constitutional setting, this technology is accepted as the first-tier test for the evaluation of chromosomal imbalances associated with intellectual disability, autism, and/or multiple congenital anomalies. Furthermore, chromosomal microarray analysis is recommended for patients undergoing invasive prenatal diagnosis with one or more major fetal structural abnormalities identified by ultrasonographic examination, and in the evaluation of intrauterine fetal demise or stillbirth when further cytogenetic analysis is desired. This technology also provides important genomic data in the diagnosis, prognosis, and therapy of neoplastic disorders, including both hematologic malignancies and solid tumors. To assist clinical laboratories in the validation of chromosomal microarray methodologies for constitutional and neoplastic applications, the American College of Medical Genetics and Genomics (ACMG) Laboratory Quality Assurance Committee has developed these updated technical laboratory standards, which replace the ACMG technical standards and guidelines for microarray analysis in constitutional and neoplastic disorders previously published in 2013.

Background/Objectives: Optical genome mapping (OGM) has recently emerged as a new technology in the clinical cytogenomics laboratories. This methodology has the ability to detect balanced and unbalanced structural rearrangements using ultra-high molecular weight DNA. This article discusses the uses of this new technology in both constitutional and somatic settings, its advantages as well as opportunity for improvements. Methods: We reviewed the medical and scientific literature for methodology and current clinical uses of OGM. Results: OGM is a recent addition to the methods used in cytogenomics laboratories and can detect a wide range of structural and copy number variations across a plethora of diseases. Conclusions: Clinical cytogenomics is an important laboratory specialty for which various technologies have been validated over the last several decades to improve detection of copy number and structural variations and their association to human disease. OGM has proven to be a powerful tool in the arsenal of clinical laboratories and provides a unified workflow for the detection of chromosomal aberrations across a wide range of diseases.

Disclaimer: ACMG Clinical Laboratory Practice Resources are developed primarily as an educational tool for clinical laboratory geneticists to help them provide quality clinical laboratory genetic services. Adherence to these practice resources is voluntary and does not necessarily assure a successful medical outcome. This Clinical Laboratory Practice Resource should not be considered inclusive of all proper procedures and tests or exclusive of other procedures and tests that are reasonably directed to obtaining the same results. In determining the propriety of any specific procedure or test, the clinical laboratory geneticist should apply his or her own professional judgment to the specific circumstances presented by the individual patient or specimen. Clinical laboratory geneticists are encouraged to document in the patient’s record the rationale for the use of a particular procedure or test, whether or not it is in conformance with this Clinical Laboratory Practice Resource . They also are advised to take notice of the date any particular guideline was adopted, and to consider other relevant medical and scientific information that becomes available after that date. It also would be prudent to consider whether intellectual property interests may restrict the performance of certain tests and other procedures. Noninvasive prenatal screening (NIPS) using cell-free DNA has been rapidly adopted into prenatal care. Since NIPS is a screening test, diagnostic testing is recommended to confirm all cases of screen-positive NIPS results. For cytogenetics laboratories performing confirmatory testing on prenatal diagnostic samples, a standardized testing algorithm is needed to ensure that the appropriate testing takes place. This algorithm includes diagnostic testing by either chorionic villi sampling or amniocentesis samples and encompasses chromosome analysis, fluorescence in situ hybridization, and chromosomal microarray.

One goal of the joint College of American Pathologists/American College of Medical Genetics and Genomics Cytogenetics Committee is to ensure the accurate detection and description of chromosomal abnormalities in both constitutional and neoplastic specimens, including hematologic neoplasms. To report a 20-year performance summary (1999-2018) of conventional chromosome challenges focusing on hematologic neoplasms. A retrospective review was performed from 1999 through 2018 to identify karyotype challenges specifically addressing hematologic neoplasms. The overall performance of participants was examined to identify potential recurring errors of clinical significance. Of 288 total conventional chromosome challenges from 1999-2018, 87 (30.2%) were presented in the context of a hematologic neoplasm, based on the provided clinical history, specimen type, and/or chromosomal abnormalities. For these 87 hematologic neoplasm challenges, 91 individual cases were provided and graded on the basis of abnormality recognition and karyotype nomenclature (ISCN, International System for Human Cytogenomic [previously Cytogenetic] Nomenclature). Of the 91 cases, 89 (97.8%) and 87 (95.6%) exceeded the required 80% consensus for grading of abnormality recognition and correct karyotype nomenclature, respectively. The 2 cases (2 of 91; 2.2%) that failed to meet the 80% consensus for abnormality recognition had complex karyotypes. The 4 cases (4 of 91; 4.4%) that failed to meet the 80% consensus for correct karyotype nomenclature were the result of incorrect abnormality recognition (2 cases), missing brackets in the karyotype (1 case), and incorrect breakpoint designation (1 case). This 20-year review demonstrates clinical cytogenetics laboratories have been and continue to be highly proficient in the detection and description of chromosomal abnormalities associated with hematologic neoplasms.

Background Chromosomal microarray (CMA) is commonly utilized in the obstetrics setting. CMA is recommended when one or more fetal structural abnormalities is identified. CMA is also commonly used to determine genetic etiologies for miscarriages, fetal demise, and confirming positive prenatal cell‐free DNA screening results. Methods In this study, we retrospectively examined 523 prenatal and 319 products‐of‐conception (POC) CMA cases tested at Nationwide Children's Hospital from 2011 to 2020. We reviewed the referral indications, the diagnostic yield, and the reported copy number variants (CNV) findings. Results. In our cohort, the diagnostic yield of clinically significant CNV findings for prenatal testing was 7.8% (n = 41/523) compared to POC testing (16.3%, n = 52/319). Abnormal ultrasound findings were the most common indication present in 81% of prenatal samples. Intrauterine fetal demise was the common indication identified in POC samples. The most common pathogenic finding observed in all samples was isolated trisomy 21, detected in seven samples. Conclusion Our CMA study supports the clinical utility of prenatal CMA for clinical management and identifying genetic etiology in POC arrays. In addition, it provides insight to the spectrum of prenatal and POC CMA results as detected in an academic hospital clinical laboratory setting that serves as a reference laboratory.

Key Clinical Message A research study utilizing whole‐genome sequence analysis for preconception carrier screening provided a genome‐first detection of a severe de novo Factor VIII mutation in a woman with implications for pregnancy management and life‐saving interventions of her newborn son, and a challenge to the existing paradigm regarding carrier testing. A research study utilizing whole‐genome sequence analysis for preconception carrier screening provided a genome‐first detection of a severe de novo Factor VIII mutation in a woman with implications for pregnancy management and life‐saving interventions of her newborn son, and a challenge to the existing paradigm regarding carrier testing.

College of American Pathologists (CAP) accreditation requirements, Clinical Laboratory Improvement Amendments of 1988 (CLIA) regulatory requirements (Table 1), and professional guidelines have been developed for genetic test reporting.1-6 These focus on data elements that are either essential or recommended for inclusion in clinical laboratory reports and in interpretative strategies for genomics data. [...]genomic reports across laboratories show marked heterogeneity in content, organization, and presentation. Differences in reporting formats and styles may affect communication between pathologists and clinicians.7,8 Previous studies have demonstrated that the variation in laboratory reporting of molecular genetic test results influences the understanding of the results and overall satisfaction of clinicians.9-11 The appearance and structure of molecular reports may, at least in part, affect the comprehension of the results by patients and nonspecialist physicians.5 In this study, we performed a structured review of clinical genomic reports from various laboratories in 5 molecular disciplines, including germline, somatic hematologic malignancies, somatic solid tumors, pharmacogenomics (PGx), and prenatal cfDNA, to document current genomic reporting practices. The groups reviewed regulatory requirements (42 CFR § 493.1291), accreditation criteria (CAP checklists related to molecular pathology and general laboratory practices [Molecular Pathology, All Common, and Laboratory General]), professional guidelines for reporting,1,2,4^ examples of clinical genomic reports, and published literature on reporting of molecular test results.9'10,12\"16 Patient-de-identified genomic reports were obtained from 31 clinical laboratories/companies in each of 5 molecular disciplines.

Evidence suggests that haematopoietic stem cells might have unexpected developmental plasticity, highlighting therapeutic potential. For example, bone-marrow-derived hepatocytes can repopulate the liver of mice with fumarylacetoacetate hydrolase deficiency and correct their liver disease. To determine the underlying mechanism in this murine model, we performed serial transplantation of bone-marrow-derived hepatocytes. Here we show by Southern blot analysis that the repopulating hepatocytes in the liver were heterozygous for alleles unique to the donor marrow, in contrast to the original homozygous donor cells. Furthermore, cytogenetic analysis of hepatocytes transplanted from female donor mice into male recipients demonstrated 80,XXXY (diploid to diploid fusion) and 120,XXXXYY (diploid to tetraploid fusion) karyotypes, indicative of fusion between donor and host cells. We conclude that hepatocytes derived form bone marrow arise from cell fusion and not by differentiation of haematopoietic stem cells.