ACMG Statements and Guidelines
These online statements and guidelines are definitive and may be cited using the digital object identifier (DOI). These recommendations are designed primarily as an educational resource for medical geneticists and other healthcare providers to help them provide quality medical genetics services; they 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. Please refer to the leading disclaimer in each document for more information.
Clinical, technical, and environmental biases influencing equitable access to clinical genetics/genomics testing: A points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Bias within medicine, when unaddressed or not mitigated, has the potential to negatively affect health equity. As genetic testing becomes increasingly endorsed by the medical community and available to the public, a working group formed by members of the Social, Ethical and Legal Issues and Diversity, Equity and Inclusion committees of the American College of Medical Genetics and Genomics (ACMG) developed this document in an effort to address current factors in which bias can occur in clinical genetic testing and within the medical genetics profession, with the goal of fostering awareness and identifying strategies to reduce bias and improve health equity.
Contributions from medical geneticists in clinical trials of genetic therapies: A points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Rare diseases are not cumulatively rare given that approximately 1 in 20 people is affected by 1 of more than 7000 known rare diseases.1 Many of these disorders have a genetic basis, and the list of US Food and Drug Administration (FDA) approved orphan drugs for rare disease is growing.2 However, therapies are still not available for most rare genetic diseases. This points to consider focuses on the growing list of nucleic acid-based technologies being explored for therapeutics, including viral- and nonviral-based gene transfer, gene editing, and messenger RNA and antisense oligonucleotide therapies, which cumulatively lead to growing optimism and require specific knowledge and considerations in the area of rare disease therapeutics.
Laboratory perspectives in the development of polygenic risk scores for disease: A points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Complex health related disorders, including some forms of cardiovascular disease, diabetes, asthma, autism, and cancer, arise through the relative contributions of genetic, environmental, and lifestyle factors over long periods of time. Unlike monogenic disorders, complex disorders develop via a cumulative effect across many genomic loci, each conferring small individual risks. Polygenic risk scores (PRSs)1 combine these small individual variant effects to predict risk for developing complex disorders (Box 1) and may be combined with monogenic disease risk and nongenetic risk factors in an integrated risk model to predict disease risk more accurately.
The clinical application of polygenic risk scores: A points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Polygenic inheritance is a non-Mendelian form of inheritance in which the risk of a trait, disorder, or disease results from the combined contribution of variants from multiple genes. Most chronic illnesses and complex disorders are multifactorial and are associated with polygenic inheritance and environmental influences. Genome-wide association studies (GWAS) evaluate the association of specific loci with various complex disorders, such as cardiovascular disease, diabetes, cancer, neuropsychiatric conditions, or individual traits, such as height and blood pressure.
Points to consider in the practice of postmortem genetic testing: A statement of the American College of Medical Genetics and Genomics (ACMG)A traditional autopsy involves both histopathological examination of tissues and toxicology studies and is often used to help obtain a postmortem diagnosis in cases of sudden death. More recently, molecular technologies including next-generation sequencing are being used to assist in establishing or supporting a diagnosis when traditional autopsies fail to uncover a cause. Next-generation sequencing methods can also be used to more fully characterize a variety of conditions identified at autopsy that are suspected of having a heritable cause.
The designated record set for clinical genetic and genomic testing: A points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Individuals have a right to access certain information in their medical records as established under the Health Insurance Portability and Accountability Act of 1996 (HIPAA).1 The specific information to which individuals have access is called a designated record set (DRS), a legal term of art defined in the HIPAA Standards for Privacy of Individually Identifiable Health Information (Privacy Rule).2 The Privacy Rule is a federal medical privacy law that applies to most clinical laboratories operating in the United States.
Solid organ transplantation in methylmalonic acidemia and propionic acidemia: A points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Methylmalonic acidemia (MMA; OMIM 251000 , OMIM 251100 , OMIM 251110 , OMIM 277410 , OMIM 277400 ) and propionic acidemia (PA; OMIM 606054 ) are inborn errors of metabolism of the propionate pathway characterized by accumulation of methylmalonic acid and propionic acid, respectively, leading to acute presentations related to metabolic acidosis and hyperammonemia, as well as chronic heterogenous complications.
Noninvasive prenatal screening (NIPS) for fetal chromosome abnormalities in a general-risk population: An evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG)This workgroup aimed to develop an evidence-based clinical practice guideline for the use of noninvasive prenatal screening (NIPS) for pregnant individuals at general risk for fetal trisomy 21, trisomy 18, or trisomy 13 and to evaluate the utility of NIPS for other chromosomal disorders.
Considerations for policymakers for improving health care through telegenetics: A points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Telegenetics, a form of telemedicine, is 2-way, interactive real-time electronic information communication between a patient and genetics health care professional(s) (ie, medical geneticists [physicians who specialize in genetics] and genetic counselors [health care workers with training in medical genetics and counseling]) as an alternate to providing health care in person at a medical office.1,2 These services include, but are not limited to, assessment, diagnosis, consultation, test result release, education, counseling, management of care, and/or aided self-management.
ACMG SF v3.1 list for reporting of secondary findings in clinical exome and genome sequencing: A policy statement of the American College of Medical Genetics and Genomics (ACMG)The American College of Medical Genetics and Genomics (ACMG) previously published guidance for reporting secondary findings (SF) in the context of clinical exome and genome sequencing in 2013, 2017, and 2021.1-3 The ACMG Secondary Findings Working Group (SFWG) and Board of Directors (BOD) have agreed that the list of recommended genes should now be updated annually, but with an ongoing goal of maintaining this as a minimum list. Reporting of SF should be considered neither a replacement for indication-based diagnostic clinical genetic testing nor a form of population screening.
Systematic evidence-based review: The application of noninvasive prenatal screening using cell-free DNA in general-risk pregnanciesNoninvasive prenatal screening (NIPS) using cell-free DNA has been assimilated into prenatal care. Prior studies examined clinical validity and technical performance in high-risk populations. This systematic evidence review evaluates NIPS performance in a general-risk population.
Clinical evaluation and etiologic diagnosis of hearing loss: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG)Hearing loss is a common and complex condition that can occur at any age, can be inherited or acquired, and is associated with a remarkably wide array of etiologies. The diverse causes of hearing loss, combined with the highly variable and often overlapping presentations of different forms of hearing loss, challenge the ability of traditional clinical evaluations to arrive at an etiologic diagnosis for many deaf and hard-of-hearing individuals. However, identifying the etiology of hearing loss may affect clinical management, improve prognostic accuracy, and refine genetic counseling and assessment of the likelihood of recurrence for relatives of deaf and hard-of-hearing individuals.
Response to Righetti et alWe thank Righetti et al1 for their interest in our article titled Screening for autosomal recessive and X-linked conditions during pregnancy and preconception: a practice resource of the American College of Medical Genetics and Genomics (ACMG).2 We were pleased to learn that the investigators from the Australian Reproductive Genetic Carrier Screening Project (ARGCSP) are in agreement with many aspects of this practice resource.
Clinical pharmacogenomic testing and reporting: A technical standard of the American College of Medical Genetics and Genomics (ACMG)Pharmacogenomic testing interrogates germline sequence variants implicated in interindividual drug response variability to infer a drug response phenotype and to guide medication management for certain drugs. Specifically, discrete aspects of pharmacokinetics, such as drug metabolism, and pharmacodynamics, as well as drug sensitivity, can be predicted by genes that code for proteins involved in these pathways. Pharmacogenomics is unique and differs from inherited disease genetics because the drug response phenotype can be drug-dependent and is often unrecognized until an unexpected drug reaction occurs or a patient fails to respond to a medication.
Measurement of lysosomal enzyme activities: A technical standard of the American College of Medical Genetics and Genomics (ACMG)Assays that measure lysosomal enzyme activity are important tools for the screening and diagnosis of lysosomal storage disorders (LSDs). They are often ordered in combination with urine oligosaccharide and glycosaminoglycan analysis, additional biomarker assays, and/or DNA sequencing when an LSD is suspected. Enzyme testing in whole blood/leukocytes, serum/plasma, cultured fibroblasts, or dried blood spots demonstrating deficient enzyme activity remains a key component of LSD diagnosis and is often prompted by characteristic clinical findings, abnormal newborn screening, abnormal biochemical findings (eg, elevated glycosaminoglycans), or molecular results indicating pathogenic variants or variants of uncertain significance in a gene associated with an LSD.
Stewardship of patient genomic data: A policy statement of the American College of Medical Genetics and Genomics (ACMG)Human genomic data linked to health records have become valuable in the quest to establish correlations between disease and genetic information. As a result, it has become increasingly common for patient genetic information obtained through clinical testing or other means to be de-identified and linked to health records for sale or transfer to a third party for research and development purposes (eg, novel drug targets, patient and provider tools for managing health care). Unlike many other elements within the de-identified data set, however, the patient’s genetic information in various forms (eg, DNA sequence, RNA sequence, aggregated variant data, optical mapping) may be sufficiently information-rich to permit reidentification of the patient using informatics tools in some cases and is considered by some to be inherently identifiable.
Points to consider to avoid unfair discrimination and the misuse of genetic information: A statement of the American College of Medical Genetics and Genomics (ACMG)In this era of precision medicine, the incorporation of genetic and genomic information, herein referred to as genetic information, into health care has gained unprecedented attention. As a result of the rapid decline in the cost of DNA sequencing, these data are now routinely used for diagnostic purposes and preventive health screening. In addition to the application of genetic information to support diagnosis and management, consumers may directly access various genetic testing–based products for medical and nonmedical uses, and some employers now offer wellness genetic testing to their employees as a benefit.
Interpretation and reporting of large regions of homozygosity and suspected consanguinity/uniparental disomy, 2021 revision: A technical standard of the American College of Medical Genetics and Genomics (ACMG)Genomic testing, including single-nucleotide variation (formerly single-nucleotide polymorphism)–based chromosomal microarray and exome and genome sequencing, can detect long regions of homozygosity (ROH) within the genome. Genomic testing can also detect possible uniparental disomy (UPD). Platforms that can detect ROH and possible UPD have matured since the initial American College of Medical Genetics and Genomics (ACMG) standard was published in 2013, and the detection of ROH and UPD by these platforms has shown utility in diagnosis of patients with genetic/genomic disorders.
Addendum: Technical standards and guidelines: Molecular genetic testing for ultra-rare disordersThis document was retired by the American College of Medical Genetics and Genomics (ACMG) Board of Directors as of May 20, 2019 with the following addendum.
Correction: Technical standards for the interpretation and reporting of constitutional copy-number variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics (ACMG) and the Clinical Genome Resource (ClinGen)The original article can be found online at https://doi.org/10.1038/s41436-019-0686-8 .
Exome and genome sequencing for pediatric patients with congenital anomalies or intellectual disability: an evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG)To develop an evidence-based clinical practice guideline for the use of exome and genome sequencing (ES/GS) in the care of pediatric patients with one or more congenital anomalies (CA) with onset prior to age 1 year or developmental delay (DD) or intellectual disability (ID) with onset prior to age 18 years.
Direct-to-consumer prenatal testing for multigenic or polygenic disorders: a position statement of the American College of Medical Genetics and Genomics (ACMG)A correction to this article is available online at https://doi.org/10.1038/s41436-021-01275-x .
Screening for autosomal recessive and X-linked conditions during pregnancy and preconception: a practice resource of the American College of Medical Genetics and Genomics (ACMG)Carrier screening began 50 years ago with screening for conditions that have a high prevalence in defined racial/ethnic groups (e.g., Tay–Sachs disease in the Ashkenazi Jewish population; sickle cell disease in Black individuals). Cystic fibrosis was the first medical condition for which panethnic screening was recommended, followed by spinal muscular atrophy. Next-generation sequencing allows low cost and high throughput identification of sequence variants across many genes simultaneously. Since the phrase “expanded carrier screening” is nonspecific, there is a need to define carrier screening processes in a way that will allow equitable opportunity for patients to learn their reproductive risks using next-generation sequencing technology.
Chromosomal microarray analysis, including constitutional and neoplastic disease applications, 2021 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG)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.
Management of individuals with germline variants in PALB2: a clinical practice resource of the American College of Medical Genetics and Genomics (ACMG)PALB2 germline pathogenic variants are associated with increased breast cancer risk and smaller increased risk of pancreatic and likely ovarian cancer. Resources for health-care professionals managing PALB2 heterozygotes are currently limited.
ACMG SF v3.0 list for reporting of secondary findings in clinical exome and genome sequencing: a policy statement of the American College of Medical Genetics and Genomics (ACMG)A correction to this article is available online at https://doi.org/10.1038/s41436-021-01278-8 .
Incidental detection of acquired variants in germline genetic and genomic testing: a points to consider statement of the American College of Medical Genetics and Genomics (ACMG)With recent advances in DNA sequencing technology, it is now possible to begin to appreciate the full scope of DNA variation that arises over the course of an individual’s lifetime.1,2 Our understanding of how the human genome changes over time and in response to external exposures is growing with the improved availability of next-generation sequencing (NGS) based testing, including exome/genome sequencing of large patient cohorts. Clinical laboratories employing NGS-based methodologies can detect many types of DNA sequence variation including those that are present at a reduced variant allele fraction (VAF) (i.e., less than the 50% expected for a heterozygous germline finding).
DNA-based screening and population health: a points to consider statement for programs and sponsoring organizations from the American College of Medical Genetics and Genomics (ACMG)A comment to this article is available online at https://doi.org/10.1038/s41436-021-01141-w .
DNA-based screening and personal health: a points to consider statement for individuals and health-care providers from the American College of Medical Genetics and Genomics (ACMG)A comment to this article is available online at https://doi.org/10.1038/s41436-021-01141-w .
Focused Revision: ACMG practice resource: Genetic evaluation of short statureAddendum to: “ACMG practice guideline: Genetic evaluation of short stature”. Laurie H. Seaver, MD and Mira Irons, MD; ACMG Professional Practice and Guidelines Committee Genetics in Medicine 11:465–470 (2009); https://doi.org/10.1097/GIM.0b013e3181a7e8f8 ; published online 02 April 2009.
Laboratory testing for fragile X, 2021 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG)Molecular genetic testing of the FMR1 gene is commonly performed in clinical laboratories. Pathogenic variants in the FMR1 gene are associated with fragile X syndrome, fragile X–associated tremor ataxia syndrome (FXTAS), and fragile X–associated primary ovarian insufficiency (FXPOI). This document provides updated information regarding FMR1 pathogenic variants, including prevalence, genotype–phenotype correlations, and variant nomenclature. Methodological considerations are provided for Southern blot analysis and polymerase chain reaction (PCR) amplification of FMR1, including triplet repeat–primed and methylation-specific PCR.
Laboratory analysis of acylcarnitines, 2020 update: a technical standard of the American College of Medical Genetics and Genomics (ACMG)Acylcarnitine analysis is a useful test for identifying patients with inborn errors of mitochondrial fatty acid β-oxidation and certain organic acidemias. Plasma is routinely used in the diagnostic workup of symptomatic patients. Urine analysis of targeted acylcarnitine species may be helpful in the diagnosis of glutaric acidemia type I and other disorders in which polar acylcarnitine species accumulate. For newborn screening applications, dried blood spot acylcarnitine analysis can be performed as a multiplex assay with other analytes, including amino acids, succinylacetone, guanidinoacetate, creatine, and lysophosphatidylcholines.
Addendum: ACMG Practice Guideline: lack of evidence for MTHFR polymorphism testingThis is an addendum to the article available online at https://doi.org/10.1038/gim.2012.165 .
Addendum: Statement on nutritional supplements and piracetam for children with Down syndromeThe original statement was published in the ACMG newsletter in 1996.
Addendum: Array-based technology and recommendations for utilization in medical genetics practice for detection of chromosomal abnormalitiesAddendum to: Genetics in Medicine 12:742–745 (2010) https://doi.org/10.1097/GIM.0b013e3181f8baad , published online 18 October 2010.
Addendum: American College of Medical Genetics guideline on the cytogenetic evaluation of the individual with developmental delay or mental retardationAddendum to: Genetics in Medicine7:650–654 (2005); https://doi.org/10.1097/01.gim.0000186545.83160.1e , published online 01 November 2005
Treatment of mucopolysaccharidosis type II (Hunter syndrome): a Delphi derived practice resource of the American College of Medical Genetics and Genomics (ACMG)Mucopolysaccharidosis, type II (MPS II, MIM 309900) is a severe lysosomal storage disease with multisystem involvement. There is one product approved by the FDA, an enzyme replacement therapy, based on a phase III trial in older, attenuated MPS II individuals. Guidance on treatment of MPS II is lacking, not only in general, but for specific clinical situations. A previous systematic evidence-based review of treatment for MPS II demonstrated insufficient strength in all data analyzed to create a definitive practice guideline based solely on published evidence.
The interface of genomic information with the electronic health record: a points to consider statement of the American College of Medical Genetics and Genomics (ACMG)Disclaimer: This statement is designed primarily as an educational resource for medical geneticists and other clinicians to help them provide quality medical services. Adherence to this statement is completely voluntary and does not necessarily assure a successful medical outcome. This statement 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 clinician should apply his or her own professional judgment to the specific clinical circumstances presented by the individual patient or specimen.
Correction: Addendum: ACMG Practice Guideline: lack of evidence for MTHFR polymorphism testingAn amendment to this paper has been published and can be accessed via a link at the top of the paper.
Points to consider when assessing relationships (or suspecting misattributed relationships) during family-based clinical genomic testing: a statement of the American College of Medical Genetics and Genomics (ACMG)Trio-based genetic analysis (typically involving a child and their biological parents) is an important tool in clinical diagnostic testing, as this type of analysis aids in developing an accurate understanding of the inheritance of variants observed in the proband.1-5 Understanding if a variant is inherited or is de novo can directly affect variant classification and result interpretation; consequently, misunderstanding the true biological relationship between analyzed samples can lead to erroneous clinical interpretations.
CFTR variant testing: a technical standard of the American College of Medical Genetics and Genomics (ACMG)Pathogenic variants in the CFTR gene are causative of classic cystic fibrosis (CF) as well as some nonclassic CF phenotypes. In 2001, CF became the first target of pan-ethnic universal carrier screening by molecular methods. The American College of Medical Genetics and Genomics (ACMG) recommended a core panel of 23 disease-causing variants as the minimal set to be included in pan-ethnic carrier screening of individuals with no family history of the disease, and these variants were usually assessed using targeted methods.
Diagnostic testing for uniparental disomy: a points to consider statement from the American College of Medical Genetics and Genomics (ACMG)In 1980, Eric Engel1 first proposed the concept of uniparental disomy (UPD), in which both homologous chromosomes are inherited from one parent, with no contribution (for that chromosome) from the other parent. In 1988, the first case of a Mendelian disorder associated with UPD was reported, in which a child with cystic fibrosis (MIM 219700) had inherited two copies of a pathogenic variant in CFTR (MIM 602421) from a heterozygous carrier mother, with no contribution from the biological father.2
Points to consider for reporting of germline variation in patients undergoing tumor testing: a statement of the American College of Medical Genetics and Genomics (ACMG)The sequencing of tumor-derived DNA to identify tumor-specific variations (biomarkers) with potential diagnostic, prognostic, or predictive therapeutic implications (hereafter, “tumor testing”) is a prominent example of precision medicine. Although the primary goal of this testing is the identification of biomarkers to guide patient management, testing tumor genomes also has the potential to uncover clinically relevant germline variation that is associated with heritable cancer susceptibility and other conditions, and carrier status for autosomal recessive disorders, if confirmed to be present in the germline.
Risk categorization for oversight of laboratory-developed tests for inherited conditions: an updated position statement of the American College of Medical Genetics and Genomics (ACMG)This document represents an update to the proposed approach of the American College of Medical Genetics and Genomics (ACMG) to categorize laboratory-developed tests (LDTs) for inherited conditions according to risk.1 Risk classification has historically been a determinant of whether, and to what extent, the US Food and Drug Administration (FDA) has overseen and regulated clinical tests. LDTs for constitutional variants continue to proliferate without a comprehensive federal regulatory framework in place.
Systematic evidence-based review: outcomes from exome and genome sequencing for pediatric patients with congenital anomalies or intellectual disabilityExome and genome sequencing (ES/GS) are performed frequently in patients with congenital anomalies, developmental delay, or intellectual disability (CA/DD/ID), but the impact of results from ES/GS on clinical management and patient outcomes is not well characterized. A systematic evidence review (SER) can support future evidence-based guideline development for use of ES/GS in this patient population.
Points to consider: is there evidence to support BRCA1/2 and other inherited breast cancer genetic testing for all breast cancer patients? A statement of the American College of Medical Genetics and Genomics (ACMG)Of all cancers that develop in women in the United States, breast cancer has the highest incidence, regardless of race or ethnicity, with an estimated 271,270 new cases and 42,260 deaths during 2019.1 Approximately 5–10% of breast cancers are estimated to result from hereditary causes, the majority of which are attributed to pathogenic or likely pathogenic (P/LP) variants in the BRCA1 and BRCA2 (BRCA1/2) genes, although other variants in genes such as PALB2, TP53, PTEN, CDH1, CHEK2, and ATM contribute.
Laboratory diagnosis of disorders of peroxisomal biogenesis and function: a technical standard of the American College of Medical Genetics and Genomics (ACMG)Peroxisomal disorders are a clinically and genetically heterogeneous group of diseases caused by defects in peroxisomal biogenesis or function, usually impairing several metabolic pathways. Peroxisomal disorders are rare; however, the incidence may be underestimated due to the broad spectrum of clinical presentations. The inclusion of X-linked adrenoleukodystrophy to the Recommended Uniform Screening Panel for newborn screening programs in the United States may increase detection of this and other peroxisomal disorders.
The use of fetal exome sequencing in prenatal diagnosis: a points to consider document of the American College of Medical Genetics and Genomics (ACMG)Approximately 2–4% of pregnancies are complicated by significant fetal structural anomalies. Given respect for reproductive autonomy, all patients diagnosed with a fetal anomaly should be offered genetic counseling, including review of options for genetic testing.1 The prenatal testing strategy and test selection should be individualized and guided by prenatal imaging findings and family history. Current options include chromosomal studies by karyotyping, fluorescence in situ hybridization, and chromosomal microarray analysis (CMA) with consideration of targeted gene-specific molecular testing for suspected disorders.
Diagnostic gene sequencing panels: from design to report—a technical standard of the American College of Medical Genetics and Genomics (ACMG)Gene sequencing panels are a powerful diagnostic tool for many clinical presentations associated with genetic disorders. Advances in DNA sequencing technology have made gene panels more economical, flexible, and efficient. Because the genes included on gene panels vary widely between laboratories in gene content (e.g., number, reason for inclusion, evidence level for gene–disease association) and technical completeness (e.g., depth of coverage), standards that address technical and clinical aspects of gene panels are needed.
Laboratory screening and diagnosis of open neural tube defects, 2019 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG)Open neural tube defects (ONTDs) include open spina bifida (OSB) and anencephaly. These defects are caused by incomplete closure of the neural tube at about 4 weeks of pregnancy. Levels of early second-trimester maternal serum (ms) alpha-fetoprotein (AFP) are sufficiently elevated in affected pregnancies to be used as a population-based screening test. The basic screening methodology was described in the late 1970s and screening programs were active a few years later. By identifying pregnancies with the highest msAFP levels, about 80% of OSB and 95% of anencephaly can be identified as early as 16 weeks gestation.