Estimating the efficacy and efficiency of cascade genetic screening

Evaluating the impact of accessible low-cost pediatric genetic testing on underserved communities in the United States

BACKGROUND

Genetic testing is at the forefront of medical diagnosis, management, and preventative care particularly within the field of nephrology, but such testing can be prohibitively expensive for patients from disadvantaged backgrounds. This study is aimed at exploring how use of a low-cost, comprehensive commercial panel could increase availability of genetic testing to patients served by an inner-city American hospital and overcome many of the obstacles faced by these patients, including lack of availability of pediatric geneticist and genetic counselors, leading to delay in care and management, cost of genetic testing, and inaccessibility of genetic testing to underserved populations.

METHODS

Single-center retrospective analysis patients who underwent genetic testing with NATERA Renasight Kidney Gene Panels run between November 2020 and October 2021.

RESULTS

Genetic testing was offered to 208 patients, with 193 tests performed, 10 pending, and 4 deferred. Seventy-six patients were found to have results of clinical significance; 117 patients were found to have a negative result, of which 79 were found to have a variant of unknown significance (VUS); and 8 of these 79 VUS were later determined to be clinically significant leading to a change in management. Patient payment data breakdown showed that of 173, 68% used public insurance coverage, 27% used commercial or private insurance, and 5% were unknown.

CONCLUSIONS

Genetic testing with the NATERA Renasight Panel provided a high positivity rate for genetic testing using next generation sequencing. It also allowed us to provide access to genetic testing to a larger population, specifically underserved and underrepresented patients. A higher resolution version of the Graphical abstract is available as Supplementary information.

Twenty-Five Years of Contemplating Genotype-Based Hereditary Hemochromatosis Population Screening

Hereditary hemochromatosis (HH) is a rather frequent, preventable disease because the progressive iron overload affecting many organs can be effectively reduced by phlebotomy. Even before the discovery of the major gene, HFE, in 1996, hemochromatosis was seen as a candidate for population-wide screening programmes. A US Centers of Disease Control and the National Human Genome Research Institute expert panel convened in 1997 to consider genotype-based HH population-wide screening and decided that the scientific evidence available at that time was insufficient and advised against. In spite of a large number of studies performed within the last 25 years, addressing all aspects of HH natural history, health economics, and social acceptability, no professional body worldwide has reverted this decision, and HH remains a life-threatening condition that often goes undetected at a curable stage.

A systematic review of theory-informed strategies used in interventions fostering family genetic risk communication

BACKGROUND

Inherited risk is a family issue. Identifying family members who carry a pathogenic genetic variant that increases risk of cancers and other chronic diseases can be lifesaving for those affected.

OBJECTIVE

The research questions are: (1) which family communication frameworks have been applied, (2) how do intervention strategies employed map to these theories, and (3) to what extent were families receptive to these strategies and communication increased?

METHODS

Manuscripts published between January 2010 and August 2020 were searched in three databases: PubMed, PsycINFO, and Web of Science.

RESULTS

Nine intervention trials were identified. All interventions were evaluated in clinical genetic counseling contexts using at least one individual-level strategy (e.g. increase knowledge). Only three focused on dyadic conversations such as preparing for relatives' information needs.

CONCLUSIONS

This systematic review posed the question whether theoretically based approaches have been applied to foster family genetic risk communication. Greater attention needs to be paid to the utilization of dyadic level and family system level theories to guide intervention developments.

PRACTICAL IMPLICATIONS

We conclude by calling for accelerating and broadening the development of interventions to enable family communication about inherited risk that are theory-based, incorporate family-systems thinking, and are conducted outside of specialty clinic settings.

An Examination of the Ethical and Legal Limits in Implementing "Traceback Testing" for Deceased Patients

This paper examines the legal and ethical aspects of traceback testing, a process in which patients who have been previously diagnosed with ovarian cancer are identified and offered genetic testing so that their family members can be informed of their genetic risk and can also choose to undergo testing. Specifically, this analysis examines the ethical and legal limits in implementing traceback testing in cases when the patient is deceased and can no longer consent to genetic testing.

Frequency of Pathogenic Germline Variants in Cancer-Susceptibility Genes in the Childhood Cancer Survivor Study

Background

Pediatric cancers are the leading cause of death by disease in children despite improved survival rates overall. The contribution of germline genetic susceptibility to pediatric cancer survivors has not been extensively characterized. We assessed the frequency of pathogenic or likely pathogenic (P/LP) variants in 5451 long-term pediatric cancer survivors from the Childhood Cancer Survivor Study.

Methods

Exome sequencing was conducted on germline DNA from 5451 pediatric cancer survivors (cases who survived ≥5 years from diagnosis; n = 5105 European) and 597 European cancer-free adults (controls). Analyses focused on comparing the frequency of rare P/LP variants in 237 cancer-susceptibility genes and a subset of 60 autosomal dominant high-to-moderate penetrance genes, for both case-case and case-control comparisons.

Results

Of European cases, 4.1% harbored a P/LP variant in high-to-moderate penetrance autosomal dominant genes compared with 1.3% in controls (2-sided P = 3 × 10-4). The highest frequency of P/LP variants was in genes typically associated with adult onset rather than pediatric cancers, including BRCA1/2, FH, PALB2, PMS2, and CDKN2A. A statistically significant excess of P/LP variants, after correction for multiple tests, was detected in patients with central nervous system cancers (NF1, SUFU, TSC1, PTCH2), Wilms tumor (WT1, REST), non-Hodgkin lymphoma (PMS2), and soft tissue sarcomas (SDHB, DICER1, TP53, ERCC4, FGFR3) compared with other pediatric cancers.

Conclusion

In long-term pediatric cancer survivors, we identified P/LP variants in cancer-susceptibility genes not previously associated with pediatric cancer as well as confirmed known associations. Further characterization of variants in these genes in pediatric cancer will be important to provide optimal genetic counseling for patients and their families.

What improves the likelihood of people receiving genetic test results communicating to their families about genetic risk?

OBJECTIVE

We currently rely on probands to communicate genetic testing results and health risks within a family to stimulate preventive behaviors, such as cascade testing. Rates of guidelines-based cascade testing are low, possibly due to low frequency or non-urgent communication of risk among family members. Understanding what is being communicated and why may help improve interventions that increase communication and rates of cascade testing.

METHODS

Participants (n = 189) who were to receive both positive and negative colorectal cancer (CRC) sequencing results completed surveys on family communication, family functioning, impact of cancer in the family, and future communication of risk and were participants in eMERGE3. Questions were taken from existing surveys and administered electronically using email and a web driven tool.

RESULTS

Common family member targets of CRC risk communication, before results were received, were mothers and fathers, then sisters and grandchildren and finally, children and brothers. A communication impact score of 0.66 (sd = 0.83) indicated low-to-moderate communication impact. Age and education were significantly associated with frequency of familial communication, but not on the cancer-related impact of familial communication.

CONCLUSIONS

There is infrequent communication about cancer risk from probands to family members.

PRACTICE IMPLICATIONS

These results demonstrate an opportunity to help families improve communication.

Family-level impact of genetic testing: integrating health economics and ethical, legal, and social implications

Tweetable abstract Health economics and ELSI can be better integrated to consider the family impacts of genetic and genomic testing.

Frequency of Pathogenic Germline Variants in Cancer-Susceptibility Genes in Patients With Osteosarcoma

Importance

Osteosarcoma, the most common malignant bone tumor in children and adolescents, occurs in a high number of cancer predisposition syndromes that are defined by highly penetrant germline mutations. The germline genetic susceptibility to osteosarcoma outside of familial cancer syndromes remains unclear.

Objective

To investigate the germline genetic architecture of 1244 patients with osteosarcoma.

Design, Setting, and Participants

Whole-exome sequencing (n = 1104) or targeted sequencing (n = 140) of the DNA of 1244 patients with osteosarcoma from 10 participating international centers or studies was conducted from April 21, 2014, to September 1, 2017. The results were compared with the DNA of 1062 individuals without cancer assembled internally from 4 participating studies who underwent comparable whole-exome sequencing and 27 173 individuals of non-Finnish European ancestry who were identified through the Exome Aggregation Consortium (ExAC) database. In the analysis, 238 high-interest cancer-susceptibility genes were assessed followed by testing of the mutational burden across 736 additional candidate genes. Principal component analyses were used to identify 732 European patients with osteosarcoma and 994 European individuals without cancer, with outliers removed for patient-control group comparisons. Patients were subsequently compared with individuals in the ExAC group. All data were analyzed from June 1, 2017, to July 1, 2019.

Main Outcomes and Measures

The frequency of rare pathogenic or likely pathogenic genetic variants.

Results

Among 1244 patients with osteosarcoma (mean [SD] age at diagnosis, 16 [8.9] years [range, 2-80 years]; 684 patients [55.0%] were male), an analysis restricted to individuals with European ancestry indicated a significantly higher pathogenic or likely pathogenic variant burden in 238 high-interest cancer-susceptibility genes among patients with osteosarcoma compared with the control group (732 vs 994, respectively; P = 1.3 × 10-18). A pathogenic or likely pathogenic cancer-susceptibility gene variant was identified in 281 of 1004 patients with osteosarcoma (28.0%), of which nearly three-quarters had a variant that mapped to an autosomal-dominant gene or a known osteosarcoma-associated cancer predisposition syndrome gene. The frequency of a pathogenic or likely pathogenic cancer-susceptibility gene variant was 128 of 1062 individuals (12.1%) in the control group and 2527 of 27 173 individuals (9.3%) in the ExAC group. A higher than expected frequency of pathogenic or likely pathogenic variants was observed in genes not previously linked to osteosarcoma (eg, CDKN2A, MEN1, VHL, POT1, APC, MSH2, and ATRX) and in the Li-Fraumeni syndrome-associated gene, TP53.

Conclusions and Relevance

In this study, approximately one-fourth of patients with osteosarcoma unselected for family history had a highly penetrant germline mutation requiring additional follow-up analysis and possible genetic counseling with cascade testing.

Genetic testing for hereditary cancer syndromes: patient recommendations for improved risk communication

Background

Multi‐gene panel testing is replacing single‐gene testing for patients with suspected hereditary cancer syndromes. The detection of a hereditary cancer syndrome allows tested individuals to initiate enhanced primary and secondary prevention efforts—where available—with a view to reduce disease burden. Current policy prevents testing programmes from communicating genetic test results with potentially affected family members, yet it is well documented that tested individuals face multiple challenges in initiating such discussions with relatives.

Objective

In response to this challenge, we sought patient recommendations about how to improve genetic risk communication to enhance interfamilial discussions about primary and secondary disease prevention.

Design

We conducted 25 semi‐structured interviews with individuals who received genetic testing through British Columbia’s Hereditary Cancer Program between 2017 and 2018. Interviews were professionally transcribed and analysed using a constant comparative approach.

Results

Participants described difficulty engaging in conversations with relatives who were resistant to receiving genetic risk information, when communicating with younger relatives and where participants reported strained familial relationships. Participants recommended that testing facilities provide a summary of results and implications and that resources be made available to prepare patients for challenging discussions with family members.

Discussion

Our study demonstrates that individuals undergoing genetic testing for suspected hereditary cancer syndromes would benefit from additional supportive resources alongside genetic counselling. Providing this on‐going support will enhance the accurate and transparent communication of risk to facilitate the uptake of cascade testing and enhanced prevention strategies.

Assessing the implications of positive genomic screening results

Aim:

Before population screening of ‘healthy’ individuals is widely adopted, it is important to consider the harms and benefits of receiving positive results and how harms and benefits may differ by age.

Subjects & methods:

Participants in a preventive genomic screening study were screened for 17 genes associated with 11 conditions. We interviewed 11 participants who received positive results.

Results:

Interviewees expressed little concern about their positive results in light of their older age, the risk condition for which they tested positive, or other pressing health concerns.

Conclusion:

Researchers and clinicians should recognize that returning positive results may not have the impact they presume given the diversity of the conditions screened and those who choose to undergo screening.

Lung function: population epidemiology and concordance in Australian children aged 11-12 years and their parents

OBJECTIVES

To describe the epidemiology of lung function in Australian children aged 11-12 years and their parents, and explore the degree of intergenerational concordance.

DESIGN

Cross-sectional study (the Child Health CheckPoint) nested in the Longitudinal Study of Australian Children (LSAC).

SETTING

Assessment centres in seven Australian cities and eight regional towns, February 2015 to March 2016. Families unable to attend a clinic appointment were offered a home visit during the same period.

PARTICIPANTS

1874 families (53% of all eligible) participated in the study. Lung function data were available for 1759 children aged 11-12 years and 1774 parents (1668 biological pairs).

OUTCOME MEASURES

Participants completed spirometry with measures including forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC) and mid expiratory flow (MEF), converted to z-scores using Global Lung Initiative equations. Parent-child concordance was assessed using Pearson's correlation coefficients and multivariable linear regression models. Survey weights and methods accounted for LSAC's complex sampling, stratification and clustering within postcodes.

RESULTS

All lung function measures followed approximately normal distributions. Mean (SD) for FEV₁, FVC and MEF z-scores in children were 0.33 (1.07), 0.83 (1.14) and -0.48 (1.09), respectively. Mean (SD) in parents were 0.28 (1.10), 0.85 (1.15) and -0.45 (1.10), respectively. Parent FEV₁, FVC and MEF were associated with child lung function with significant positive correlation coefficients (0.22, 95% CI 0.17 to 0.26; 0.24, 95% CI 0.20 to 0.29; and 0.24, 95% CI 0.20 to 0.29, respectively).

CONCLUSIONS

Mean lung volumes were larger but with smaller airway size than international standards for both parents and children in this population sample. Modest associations between parent and child lung function highlight the potential for better identification of 'at risk' populations. Therefore, these findings may aid the development of health policy that aims to prevent the onset or limit the progression of lung disease.

Modified capture-recapture estimates of the number of families with Lynch syndrome in Central Ohio

Past methods for estimating the population frequency of familial cancer syndromes have used cases and controls ignoring the familial nature of genetic disease. In this study we modified the capture-recapture method from ecology to estimate the number of families in central Ohio with Lynch syndrome (LS). We screened 1566 colorectal cancer cases and 545 endometrial cancer cases in central Ohio from 1999 to 2005 and identified 58 with LS. We screened an additional 3346 colorectal and 342 endometrial cancer cases from 2013 to 2016 and identified 149 with LS. We found 12 LS mutations shared between families observed in the first and second studies. We identified three individuals between studies who were closely related and eight who were more distantly related. We used identified family relationships and genetic test results to estimate family size and structure. Applying a modified capture-recapture method we estimate 1693 3-generation families in the area who have 288 unique LS causing mutations. Comprehensive colorectal and endometrial cancer screening will take about 20 years to identify 50% of families with LS. This is the first time that the capture-recapture method has been applied to estimate the burden of families with a specific heritable disease. Family structure reveals the potential extent of prevention and the time necessary to identify a proportion of families with LS.

Regional Body Fat Changes and Metabolic Complications in Children With Dunnigan Lipodystrophy-Causing LMNA Variants

CONTEXT

Familial partial lipodystrophy, Dunnigan variety (FPLD2) is a rare autosomal-dominant disorder due to heterozygous missense lamin A/C (LMNA) mutations. Subjects with FPLD2 gradually lose fat from the upper and lower extremities but gain fat in the face and neck around puberty. However, the precise onset of body fat changes and metabolic complications during childhood remains unknown.

OBJECTIVE

To compare metabolic parameters and regional body fat in children with FPLD2 with the sex- and age-matched controls from the National Health and Nutrition Examination Survey (NHANES) 2005 to 2010.

METHODS

We measured fasting serum triglycerides, glucose, and skinfold thicknesses in all children (aged 1 to 18 years) harboring FPLD2-causing LMNA mutations and determined regional body fat by dual-energy X-ray absorptiometry in those aged ≥8 years.

RESULTS

Thirty-two affected females and 14 males participated. The lower limb fat in all affected females, except one, was below or equal to the first percentile and in two affected males was below the fifth percentile for NHANES. One female subject with FPLD2 followed from age 6 to 16 years revealed marked loss of extremity fat much before thelarche. Serum triglycerides were higher in females with FPLD2 aged 7 to 18 years compared with controls (median 208 vs 70 mg/dL; P < 0.0001) and showed inverse correlation with extremity skinfolds. Serum triglycerides in males with FPLD2 were not significantly different than controls.

CONCLUSIONS

The onset of fat loss from the extremities, especially in girls with FPLD2, occurs well before the onset of puberty. High serum triglycerides are seen in young females with FPLD2 with severe loss of fat from the extremities.

Rare single gene disorders: estimating baseline prevalence and outcomes worldwide

As child mortality rates overall are decreasing, non-communicable conditions, such as genetic disorders, constitute an increasing proportion of child mortality, morbidity and disability. To date, policy and public health programmes have focused on common genetic disorders. Rare single gene disorders are an important source of morbidity and premature mortality for affected families. When considered collectively, they account for an important public health burden, which is frequently under-recognised. To document the collective frequency and health burden of rare single gene disorders, it is necessary to aggregate them into large manageable groupings and take account of their family implications, effective interventions and service needs. Here, we present an approach to estimate the burden of these conditions up to 5 years of age in settings without empirical data. This approaches uses population-level demographic data, combined with assumptions based on empirical data from settings with data available, to provide population-level estimates which programmes and policy-makers when planning services can use.

The genetics and screening of familial hypercholesterolaemia

Familial Hypercholesterolaemia is an autosomal, dominant genetic disorder that leads to elevated blood cholesterol and a dramatically increased risk of atherosclerosis. It is perceived as a rare condition. However it affects 1 in 250 of the population globally, making it an important public health concern. In communities with founder effects, higher disease prevalences are observed.

We discuss the genetic basis of familial hypercholesterolaemia, examining the distribution of variants known to be associated with the condition across the exons of the genes LDLR, ApoB, PCSK9 and LDLRAP1. We also discuss screening programmes for familial hypercholesterolaemia and their cost-effectiveness. Diagnosis typically occurs using one of the Dutch Lipid Clinic Network (DCLN), Simon Broome Register (SBR) or Make Early Diagnosis to Prevent Early Death (MEDPED) criteria, each of which requires a different set of patient data. New cases can be identified by screening the family members of an index case that has been identified as a result of referral to a lipid clinic in a process called cascade screening. Alternatively, universal screening may be used whereby a population is systematically screened.

It is currently significantly more cost effective to identify familial hypercholesterolaemia cases through cascade screening than universal screening. However, the cost of sequencing patient DNA has fallen dramatically in recent years and if the rate of progress continues, this may change.

Addressing key issues in the consanguinity-related risk of autosomal recessive disorders in consanguineous communities: lessons from a qualitative study of British Pakistanis

Currently, there is no consensus regarding services required to help families with consanguineous marriages manage their increased genetic reproductive risk. Genetic services for communities with a preference for consanguineous marriage in the UK remain patchy, often poor. Receiving two disparate explanations of the cause of recessive disorders (cousin marriage and recessive inheritance) leads to confusion among families. Further, the realisation that couples in non-consanguineous relationships have affected children leads to mistrust of professional advice. British Pakistani families at-risk for recessive disorders lack an understanding of recessive disorders and their inheritance. Such an understanding is empowering and can be shared within the extended family to enable informed choice. In a three-site qualitative study of British Pakistanis, we explored family and health professional perspectives on recessively inherited conditions. Our findings suggest, firstly, that family networks hold strong potential for cascading genetic information, making the adoption of a family-centred approach an efficient strategy for this community. However, this is dependent on provision of high-quality and timely information from health care providers. Secondly, families' experience was of ill-coordinated and time-starved services, with few having access to specialist provision from Regional Genetics Services; these perspectives were consistent with health professionals' views of services. Thirdly, we confirm previous findings that genetic information is difficult to communicate and comprehend, further complicated by the need to communicate the relationship between cousin marriage and recessive disorders. A communication tool we developed and piloted is described and offered as a useful resource for communicating complex genetic information.

Aligning policy to promote cascade genetic screening for prevention and early diagnosis of heritable diseases

Cascade genetic screening is a methodology for identifying and testing close blood relatives of individuals at increased risk for heritable conditions and follows a sequential process, minimizing testing costs and the number of family members who need to be tested. It offers considerable potential for cost savings and increased awareness of heritable conditions within families. CDC-classified Tier 1 genomic applications for hereditary breast and ovarian cancer syndrome (HBOC), Lynch Syndrome (LS), and familial hypercholesterolemia (FH) are recommended for clinical use and support the use of cascade genetic screening. Most individuals are unaware of their increased risk for heritable conditions such as HBOC, LS, and FH. Consistent implementation of cascade genetic screening could significantly increase awareness and prevention of heritable conditions. Limitations to effective implementation of cascade genetic screening include: insufficient genetic risk assessment and knowledge by a majority of healthcare providers without genetics credentials; a shortage of genetic specialists, especially in rural areas; a low rate of reimbursement for comprehensive genetic counseling services; and an individual focus on prevention by clinical guidelines and insurance coverage. The family-centric approach of cascade genetic screening improves prevention and early diagnosis of heritable diseases on a population health level. Cascade genetic screening could be better supported and augmented through changes in health policy.

Communication and technology in genetic counseling for familial cancer

When a cancer predisposing germline mutation is detected in an index case, the presence of the underlying syndrome is confirmed and the potential for predictive testing of at-risk relatives is established. However, the reporting of a positive family history does not routinely lead to communication of information about risk to close, much less distant relatives. This review summarizes information technology utilized to address penetration or 'reach' of knowledge of risk within extended families, including the use of telephone and video counseling to reach distant patients, and anticipate novel internet-based processes for communication between investigators and relatives.

Attitudes and opinions of pregnant women who are not offered cystic fibrosis carrier screening

Cystic fibrosis (CF) is the most common severe, autosomal recessive disease among Caucasians. A population-based CF carrier screening programme was implemented in Victoria, Australia, in 2006. Carrier screening for CF is currently only offered in the private health system. The aim of this study was to determine the attitudes and opinions of pregnant women in the public health system, towards screening for CF. Pregnant women were recruited in the antenatal clinics of two public hospitals, and invited to participate in the study. Results of this study were compared with previous studies where screening for CF carrier status was offered. Of the participants (n=158), the majority were aged 25-34 years old (66.1%) and were Caucasian (45.8%). Compared with those who were offered screening (reported in previous studies) participants in the current study were younger, had a lower level of education and a lower income. Knowledge was significantly lower in those who were not offered screening compared with those who were offered screening. The majority of participants believe CF carrier screening should be offered in the public health system (80.5%) and almost half would have liked to receive an offer of screening during their current pregnancy (49.7%). In order for the programme to be equitable, screening for CF carrier status needs to be offered in both the public and private health system and ideally should be at no cost to the user.

Further evidence of mutational heterogeneity of the XPC gene in Tunisian families: a spectrum of private and ethnic specific mutations

Xeroderma Pigmentosum (XP) is a rare recessive autosomal cancer prone disease, characterized by UV hypersensitivity and early appearance of cutaneous and ocular malignancies. We investigated four unrelated patients suspected to be XP-C. To confirm linkage to XPC gene, genotyping and direct sequencing of XPC gene were performed. Pathogenic effect of novel mutations was confirmed by reverse Transciptase PCR. Mutation screening revealed the presence of two novel mutations g.18246G>A and g.18810G>T in the XPC gene (NG_011763.1). The first is present in one patient XP50NEF, but the second is present in three unrelated patients (XP16KEB, XP28SFA, and XP45GB). These 3 patients are from three different cities of Southern Tunisia and bear the same haplotype, suggesting a founder effect. Reverse Transciptase PCR revealed the absence of the XPC mRNA. In Tunisia, as observed in an other severe genodermatosis, the mutational spectrum of XP-C group seems to be homogeneous with some clusters of heterogeneity that should be taken into account to improve molecular diagnosis of this disease.

Screening for hereditary haemochromatosis

Hereditary haemochromatosis (HH) is a common autosomal recessive disorder of iron overload in Caucasian populations. Clinical manifestations usually occur in individuals homozygous for the C282Y mutation in the HFE gene product and who have developed significant iron loading. Current screening methods can detect affected individuals either prior to or early during disease evolution, enabling early introduction of phlebotomy treatment that can normalise life expectancy. Evaluation of possible iron overload, via measurement of serum transferrin saturation and ferritin level, is the most appropriate initial test for those subjects presenting clinically for evaluation. HFE genotyping, when combined with serum biochemical measurements, defines the presence of likely iron overload and the underlying genetic disorder and is the preferred initial screening modality for families of an affected individual. Definitive proof of iron overload requires measurement of hepatic iron concentration or total iron burden via therapeutic phlebotomy; elevated serum ferritin level alone is not adequate. We now recognise that the natural history of HH is not as discrete as previously believed, because genetic and environmental modifiers of disease penetrance are increasingly identified as influencing the clinical expression of HH. In fact, a minority of C282Y homozygotes develop classical 'iron overload disease', although it has recently emerged that the disorder may predispose to breast and colorectal cancer. Uncertainties as to the true clinical impact of the condition at a population level lead to current recommendations of cascade screening of families of affected patients, case-finding in high-risk groups, such as patients with clinical manifestations consistent with the diagnosis, and a high level of clinical awareness in the community to facilitate early diagnosis. Generalised population screening is not presently recommended.

Genetic screening

Current approaches to genetic screening include newborn screening to identify infants who would benefit from early treatment, reproductive genetic screening to assist reproductive decision making, and family history assessment to identify individuals who would benefit from additional prevention measures. Although the traditional goal of screening is to identify early disease or risk in order to implement preventive therapy, genetic screening has always included an atypical element-information relevant to reproductive decisions. New technologies offer increasingly comprehensive identification of genetic conditions and susceptibilities. Tests based on these technologies are generating a different approach to screening that seeks to inform individuals about all of their genetic traits and susceptibilities for purposes that incorporate rapid diagnosis, family planning, and expediting of research, as well as the traditional screening goal of improving prevention. Use of these tests in population screening will increase the challenges already encountered in genetic screening programs, including false-positive and ambiguous test results, overdiagnosis, and incidental findings. Whether this approach is desirable requires further empiric research, but it also requires careful deliberation on the part of all concerned, including genomic researchers, clinicians, public health officials, health care payers, and especially those who will be the recipients of this novel screening approach.

The Cost-Effectiveness of Screening for Hereditary Hemochromatosis in Germany: A Remodeling Study

Objective . Genetic tests for hereditary hemochromatosis (HH) are currently included in the German ambulatory care reimbursement scheme but only for symptomatic individuals and the offspring of HH patients. This study synthesizes the most current evidence to examine whether screening in the broader population is cost-effective and to identify the best choice of initial and follow-up screening tests. Methods . A probabilistic decision-analytic model was constructed to calculate cost per life year gained (LYG) for HH screening among male Caucasians aged 30. Three strategies were considered in both the general population and male offspring of HH patients: phenotypic (transferrin saturation, TS), genotypic (C282Y mutation), and sequential (genotype if TS is elevated) screening. Results . The incremental cost-effectiveness of sequential screening among male offspring, sequential population-wide screening, and genotypic screening is 41 000, 124 000, and 161 000 /LYG, respectively. All other strategies were subject to simple or extended dominance. The results are subject to high uncertainty. The most influential parameters in the deterministic one-way sensitivity analysis are discounting of life years gained and the adherence of patients to preventive phlebotomy. Discussion . The current German policy of only screening at-risk individuals is consistent with health economic decision making based on typically accepted thresholds. However, conducting the DNA test after the first elevated TS result is more cost-effective than waiting for a second TS result as recommended by the German guidelines. Further empirical work regarding adherence to long-term prevention recommendations and explicit and well-justified guidance for the choice of discount rates in German economic evaluation are needed.

On the testing load incurred by cascade genetic carrier screening for Mendelian disorders: a brief report

One criterion to decide to whom molecular genetic carrier testing should be provided is an individual's carrier risk, taking into account his or her affection status and degree of relatedness to an overt carrier. We have derived formulas to calculate the testing load incurred to a public health system following such a cascade screening strategy. While the testing load turns out to be moderate for individual diseases at meaningful risk thresholds (i.e., 1%-5%), a substantial proportion of the population would have to be tested if all known single gene disorders were to be included in a cascade screening program.

Cascade genetic testing for mismatch repair gene mutations

Mismatch repair gene mutation carriers have a high risk of developing colorectal cancer, and can benefit from appropriate surveillance. A combined population based ascertainment cascade genetic testing approach provides a systematic and potentially effective strategy for identifying such carriers. We have developed a Markov Chain computer model system which simulates various factors influencing cascade genetic testing; including demographics, uptake, genetic epidemiology and family size. This was used to evaluate cascade genetic testing for mismatch repair gene mutations in theory and practice. Simulations focussed on the population of Scotland by way of illustration, and were based on a 20-year programme in which index cases were ascertained from colorectal cancer cases aged<55 years at onset. Results indicated that without practical barriers to cascade genetic testing, 545 (95% CI=522, 568) carriers could be identified; 42% of the population total. This comprised approximately 140 index cases, 302 asymptomatic relatives and 104 previously affected relatives. However, when realistic ascertainment and acceptance rates were used to inform simulations, only 257 (95% CI=246, 268) carriers, about 20% of the carrier population, were identifiable. Of these approximately 112 were index cases, 108 were asymptomatic relatives, and 37 were previously affected relatives. This contrast emphasises the importance of ascertainment and acceptance rates. Likewise the low number of index cases shows that case identification is a limiting factor. In the absence of robust data from epidemiological studies, these findings can inform decisions about the use of cascade genetic testing for mismatch repair gene mutations.

EuroGentest: DNA-based testing for heritable disorders in Europe

OBJECTIVES

Regarding the recent attention to develop policies regarding the provision of clinical genetic testing services, access to, acceptance, utilisation and regulation of genetic services was investigated in selected European countries as well as one non-European country.

METHODS

Data were collected on the basis of relevant international reports and sources accessible via the internet, from self- designed, internationally administered surveys and with the help of a panel of experts from European countries participating in several workshops as well as from National European Societies of Human Genetics.

RESULTS

A selection of divergent health care systems was reviewed and compared (e.g. Finland, Germany, Portugal, Sweden, UK, France, Italy, Spain, Czech Republic, Lithuania and Serbia/Montenegro). For the evaluation of clinical validity and utility of genetic testing, background information was provided focussing on DNA-based testing for heritable disorders with a strong genetic component (usually due to the action of a single gene).

CONCLUSIONS

There is great heterogeneity in genetic testing services among the countries surveyed. It is premature to mandate that genetic testing provided by clinical services meets professional standards regarding clinical validity and utility, because there is to date no consensus within the scientific community and among health care providers to what extent clinical validity and utility can and need to be assessed. Points to consider in the process of developing such standards are proposed.

Diagnosis of familial hypercholesterolemia in general practice using clinical diagnostic criteria or genetic testing as part of cascade genetic screening

BACKGROUND

Too few familial hypercholesterolemia (FH) patients are diagnosed. The most cost-effective strategy to diagnose FH is to examine first-degree relatives of already diagnosed patients. This is referred to as cascade genetic screening.

METHODS AND RESULTS

One thousand eight hundred and five first-degree relatives of index patients with molecularly defined FH consented to cascade genetic screening by the use of molecular genetic testing. Of these, 44.8% were mutation carriers and 55.2% were noncarriers. Only 44.2% of the mutation carriers were on lipid-lowering drugs at the time of genetic testing. Of these, only 9.4% had a value for total serum cholesterol below 5 mM. Among adult mutation carriers who were not on lipid-lowering treatment at the time of genetic testing, reductions in total serum cholesterol and low-density lipoprotein cholesterol of 18.4% (p < 0.0001) and 25.3% (p < 0.0001), respectively, were observed 6 months after genetic testing. It is assumed that this improvement in the lipid profile is due to a definite diagnosis obtained by molecular genetic testing. By using the results of genetic testing as the gold standard for diagnosis of FH, data from a questionnaire filled out by the relatives showed that the use of clinical criteria to diagnose FH in general practice had a sensitivity of 46.2% and a specificity of 88.0%.

CONCLUSIONS

The use of clinical diagnostic criteria to diagnose FH in general practice identifies only approximately 50% of FH patients. Molecular genetic testing as part of cascade genetic screening is an efficient tool to diagnose patients, leading to significant improvement in the lipid profile. It should therefore be implemented in clinical medicine.

Current impact of gene technology on healthcare

OBJECTIVES

It has been claimed that gene technology will induce revolutionary changes in healthcare. This paper investigates how and to what extent these changes have been economically assessed.

METHODS

A generic framework was developed to distinguish between methodologically similar evaluations of healthcare technology. Methodological issues and the current state of economic evidence concerning human DNA technology were extracted from publications within these groups of evaluations.

RESULTS

Economic evaluations of "healthcare consisting of gene technology" were identified primarily for in vitro diagnostics for hereditary disease and others for pharmacogenetics and molecular pathology. "Healthcare enabled by gene technology" is far more encompassing and includes, e.g., biotechnology drugs for which various health economic evaluations can be found. Yet here, the impact of gene technology intertwines with the impact of other technologies and is therefore hardly susceptible to evaluation. The fields of evaluation may be classified best according to the two dimensions "purpose" and "stage of development". Current evaluations cover screening, diagnostic and treatment technologies in investigational, new and established stages. Apart from prenatal screening, healthcare consisting of gene technology was cost saving only for genotype tests replacing continuous phenotype tests and for one pharmacogenetic test. Conclusive evidence of favourable cost-effectiveness ratios is available only for few conditions.

CONCLUSION

Hypotheses about the impact of gene technology on healthcare must be explicit about the definition of "genetic" medicine. A general statement regarding healthcare enabled by gene technology is not possible. Based on current evidence, an era of healthcare consisting of gene technology built on widespread predictive testing is not desirable from a health economic viewpoint.

Clinical applications of Genome Polymorphism Scans

Applications of Genome Polymorphism Scans range from the relatively simple such as gender determination and confirmation of biological relationships, to the relatively complex such as determination of autozygosity and propagation of genetic information throughout pedigrees. Unlike nearly all other clinical DNA tests, the Scan is a universal test--it covers all people and all genes. In balance, I argue that the Genome Polymorphism Scan is the most powerful, affordable clinical DNA test available today.

Hereditary hemochromatosis: genetic complexity and new diagnostic approaches

Since the discovery of the hemochromatosis gene (HFE) in 1996, several novel gene defects have been detected, explaining the mechanism and diversity of iron-overload diseases. At least 4 main types of hereditary hemochromatosis (HH) have been identified. Surprisingly, genes involved in HH encode for proteins that all affect pathways centered around liver hepcidin synthesis and its interaction with ferroportin, an iron exporter in enterocytes and macrophages. Hepcidin concentrations in urine negatively correlate with the severity of HH. Cytokine-mediated increases in hepcidin appear to be an important causative factor in anemia of inflammation, which is characterized by sequestration of iron in the macrophage system. For clinicians, the challenge is now to diagnose HH before irreversible damage develops and, at the same time, to distinguish progressive iron overload from increasingly common diseases with only moderately increased body iron stores, such as the metabolic syndrome. Understanding the molecular regulation of iron homeostasis may be helpful in designing innovative and reliable DNA and protein tests for diagnosis. Subsequently, evidence-based diagnostic strategies must be developed, using both conventional and innovative laboratory tests, to differentiate between the various causes of distortions of iron metabolism. This review describes new insights in mechanisms of iron overload, which are needed to understand new developments in diagnostic medicine.

Reverse cascade screening of newborns for hereditary haemochromatosis: a model for other late onset diseases?

BACKGROUND

Genetic testing can determine those at risk for hereditary haemochromatosis (HH) caused by HFE mutations before the onset of symptoms. However, there is no optimum screening strategy, mainly owing to the variable penetrance in those who are homozygous for the HFE Cys282Tyr (C282Y) mutation. The objective of this study was to identify the majority of individuals at serious risk of developing HFE haemochromatosis before they developed life threatening complications.

METHODS

We first estimated the therapeutic penetrance of the C282Y mutation in people living in la Somme, France, using genetic, demographic, biochemical, and follow up data. We examined the benefits of neonatal screening on the basis of increased risk to relatives of newborns carrying one or two copies of the C282Y mutation. Between 1999 and 2002, we screened 7038 newborns from two maternity hospitals in the north of France for the C282Y and His63Asp (H63D) mutations in the HFE gene, using bloodspots collected on Guthrie cards. Family studies and genetic counselling were undertaken, based on the results of the baby's genotype.

FINDINGS

In la Somme, we found that 24% of the adults homozygous for the C282Y mutation required at least 5 g iron to be removed to restore normal iron parameters (that is, the therapeutic penetrance). In the reverse cascade screening study, we identified 19 C282Y homozygotes (1/370), 491 heterozygotes (1/14) and 166 compound heterozygotes (1/42) in 7038 newborns tested. The reverse cascade screening strategy resulted in 80 adults being screened for both mutations. We identified 10 previously unknown C282Y homozygotes of whom six (four men and two women) required venesection. Acceptance of neonatal screening was high; parents understood the risks of having HH and the benefits of early detection, but a number of parents were reluctant to take the test themselves. Neonatal screening for HH is straightforward. Reverse cascade screening increased the efficiency of detecting affected adults with undiagnosed haemochromatosis. This strategy allows almost complete coverage for HH and could be a model for efficient screening for other late onset genetic diseases.

The molecular genetics of haemochromatosis

The molecular basis of haemochromatosis has proved more complex than expected. After the 1996 identification of the main causative gene HFE and confirmation that most patients were homozygous for the founder C282Y mutation, it became clear that some families were linked to rarer conditions, first named 'non-HFE haemochromatosis'. The genetics of these less common forms was intensively studied between 2000 and 2004, leading to the recognition of haemojuvelin (HJV), hepcidin (HAMP), transferrin receptor 2 (TFR2) and ferroportin-related haemochromatosis, and opening the way for novel hypotheses such as those related to digenic modes of inheritance or the involvement of modifier genes. Molecular studies of rare haemochromatosis disorders have contributed to our understanding of iron homeostasis. In turn, recent findings from studies of knockout mice and functional studies have confirmed that HAMP plays a central role in mobilization of iron, shown that HFE, TFR2 and HJV modulate HAMP production according to the body's iron status, and demonstrated that HAMP negatively regulates cellular iron efflux by affecting the ferroportin cell surface availability. These data shed new light on the pathophysiology of all types of haemochromatosis, and offer novel opportunities to comment on phenotypic differences and distinguish mutations.

Cascade genetic screening for familial hypercholesterolemia

Familial hypercholesterolemia (FH) is caused by a mutation in the low-density lipoprotein receptor gene and is characterized by hypercholesterolemia, xanthomas, and premature coronary heart disease. Heterozygotes typically have values for total serum cholesterol in the range of 7-15 mmol/l and efficient lipid-lowering drug therapy is available. However, only approximately 20% of patients are diagnosed and less than 10% are being adequately treated. The most cost-effective strategy to diagnose patients with FH is to screen close relatives of patients already diagnosed with FH. This is referred to as cascade genetic screening. This review focuses on organization of a cascade genetic screening program for FH as well as cost-efficiency assessments, health benefits, possible adverse effects, and the screening of children. The author concludes that cascade genetic screening for FH leads to health benefits and is cost-effective without causing psychological or social damage. Accordingly, national cascade genetic screening programs for FH should be part of ordinary health care.

Mutations of the HFE gene among Turkish hereditary hemochromatosis patients

Since the discovery of the HFE gene, C282Y and H63D mutations have been reported as significantly correlated with clinically manifested hereditary hemochromatosis (HH). As the other genes involved in iron metabolism have been described, non-HFE cases of HH have been identified. Since in the general Turkish population, the C282Y mutation is not found and the H63D mutation is of high frequency, we aimed to determine mutations in the HFE genes in our patients with HH. The HFE gene of the five patients with HH were sequenced. C282Y mutation was absent, and all HH patients were heterozygote for H63D mutation. No other mutation was found in HFE gene by sequencing. Although the higher allele frequency of the H63D mutation in Turkish HH patients than in the general population implies a role of the H63D mutation in iron overload, there is a strong possibility that Turkish HH patients have non-HFE hemochromatosis.

Population genetic screening programmes: principles, techniques, practices, and policies

This paper examines the professional and scientific views on the principles, techniques, practices, and policies that impact on the population genetic screening programmes in Europe. This paper focuses on the issues surrounding potential screening programmes, which require further discussion before their introduction. It aims to increase, among the health-care professions and health policy-makers, awareness of the potential screening programmes as an issue of increasing concern to public health. The methods comprised primarily the review of the existing professional guidelines, regulatory frameworks and other documents related to population genetic screening programmes in Europe. Then, the questions that need debate, in regard to different types of genetic screening before and after birth, were examined. Screening for conditions such as cystic fibrosis, Duchenne muscular dystrophy, familial hypercholesterolemia, fragile X syndrome, hemochromatosis, and cancer susceptibility was discussed. Special issues related to genetic screening were also examined, such as informed consent, family aspects, commercialization, the players on the scene and monitoring genetic screening programmes. Afterwards, these questions were debated by 51 experts from 15 European countries during an international workshop organized by the European Society of Human Genetics Public and Professional Policy Committee in Amsterdam, The Netherlands, 19-20, November, 1999. Arguments for and against starting screening programmes have been put forward. It has been questioned whether genetic screening differs from other types of screening and testing in terms of ethical issues. The general impression on the future of genetic screening is that one wants to 'proceed with caution', with more active impetus from the side of patients' organizations and more reluctance from the policy-makers. The latter try to obviate the potential problems about the abortion and eugenics issues that might be perceived as a greater problem than it is in reality. However, it seems important to maintain a balance between a 'professional duty of care' and 'personal autonomy'.

Screening for hemochromatosis: patients with liver disease, families, and populations

Hereditary hemochromatosis is a common autosomal- recessive disorder of iron overload usually occurring in individuals who are homozygous for a C282Y mutation in the hemochromatosis (HFE) gene. Current screening methods can detect affected individuals early in disease pathogenesis, enabling early institution of effective treatment that can restore normal life expectancy. Phenotypic screening of adults using transferrin saturation and serum ferritin levels identifies the majority of individuals who develop iron overload. HFE genotyping, when combined with serum biochemical measurements, has reduced reliance on liver biopsy as a diagnostic tool and is the preferred initial screening modality for families with an affected individual. Genetic testing has altered previously held views regarding the high level of penetrance of the disease. Although the majority of C282Y homozygotes develop increased body iron stores, end-organ damage occurs much less frequently than previously thought. Screening is recommended in high-risk groups and in those with a high index of clinical suspicion. Opportunistic screening during routine health assessments may also be recommended. However, large-scale screening of the average-risk population is not recommended on the basis of current evidence.

Nonsyndromic seizure disorders: epilepsy and the use of the internet to advance research

The progress in understanding the genetics of nonsyndromic epilepsy is the direct result of dramatic advances made by the Human Genome Project. The development of thousands of precisely mapped genetic markers and the nearly complete sequencing of the entire human genome in 2001 allowed genetic researchers in epilepsy to identify many loci and genes as causal in inherited idiopathic epilepsy. This substantial increase in information has required the development of accurate and online bioinformatic databases. Only the Internet can enable such large amounts of precise DNA sequence information to be transferred to researchers. Along with the construction of these databases has been the development of efficient search algorithms for specific DNA sequences and genetic information. This article summarizes the effect that this burst of new genomic information has had on research aimed at discovering the underlying genetic factors for nonsyndromic epilepsy. Many of the web sites important to epilepsy gene discovery are listed and discussed in this article, including sites with extensive information on genetic markers, genetic analysis, gene sequence, gene expression, gene mutations, and DNA sequence variation. Continued acquisition of information on naturally occurring DNA sequence variants will greatly help research directed towards understanding the genetic susceptibility of the common, nonsyndromic epilepsies and will lead to the promise of personalized medicine.

Genetics of haemochromatosis

After identification of the hereditary haemochromatosis gene HFE, and receipt of confirmation that most patients with the condition were homozygous for a single, founder mutation (C282Y), most assumed that C282Y would be a prevalent, highly penetrant mutation in a gene that plays a key part in the regulation of iron absorption and of whole-body iron homoeostasis. With carrier rates of between 10% and 15%, and a homozygote frequency of about one-in-150 in people of northern European descent, C282Y is certainly prevalent. However, it is not highly penetrant. The pronounced variation in phenotype in individuals with the same gene mutation has prompted the search for modifier genes at other loci, and for environmental factors that might affect expression of the condition. Progress in our understanding of how HFE regulates the absorption of dietary iron has been slow, but much can be learnt from the study of the rare instances of haemochromatosis that involve mutations in newly-identified iron-metabolism genes, such as TFR2--a transferrin receptor isoform--and ferroportin1/Ireg1/mtp1--an intestinal iron transporter. The availability of definitive information on penetrance and the identity of genetic modifiers will aid the debate on whether population screening for haemochromatosis should be undertaken or whether alternative strategies should be implemented to improve early detection.

High "population attributable fraction" for coronary heart disease mortality among relatives in monogenic familial hypercholesterolemia

PURPOSE

To estimate "population attributable fraction" (PAF) for coronary heart disease (CHD) mortality in a population of first-degree relatives of patients with monogenic familial hypercholesterolemia (FH) compared with the PAF for hypercholesterolemia in the general population.

METHODS

PAF was calculated as [f(R - 1)/[1 + f(R - 1)]], where f is the frequency of the risk factor (hypercholesterolemia) and R is the relative risk for the association of hypercholesterolemia and CHD death. For FH relatives, f was assumed to be 50%, based on a fully penetrant, dominant mode of inheritance, and R values were obtained from the prospective Simon Broome Register data. PAFs for hypercholesterolemia and CHD death in the general population were based on the Framingham risk equations for the 95th percentile of cholesterol and CHD mortality.

RESULTS

Over all ages, 44% and 57% of 5-year CHD mortality could potentially be prevented among male and female first-degree relatives in FH families, respectively, by cholesterol reduction. In contrast, values for 5-year CHD death for hypercholesterolemia in the general population were uniformly lower at all ages, with overall 5% and 10% of fatal CHD prevented among men and women, respectively.

CONCLUSION

These results strongly support the view that family based testing strategies of relatives of probands with monogenic hypercholesterolemia, followed by effective lipid lowering drug treatment, is a highly effective way of reducing CHD deaths among these relatives.

Genetic testing for HFE hemochromatosis in Australia: the value of testing relatives of simple heterozygotes

BACKGROUND

It is unclear whether screening of relatives of C282Y and H63D heterozygotes (other than compound heterozygotes) for hemochromatosis will detect sufficient numbers of cases to justify introduction of this screening strategy.

METHODS

Conditional probabilities were determined using published Australian allele frequencies and penetrance data to determine the detection rate of hemochromatosis by testing the siblings and offspring of heterozygotes (subjects with only one HFE mutation).

RESULTS

The number of individuals who are at risk of developing increased body iron stores because of HFE mutations is substantially higher (1 in 80) than previously estimated. In addition, 33% of the Australian population are heterozygous for either C282Y or H63D. Based on population estimates, the relative risk to the offspring of C282Y and H63D heterozygotes of developing increased iron stores is 4.1 and 1.5, respectively, while the relative risk to each sibling is 2.3 and 1, respectively. The risk of developing clinical features of hemochromatosis or hepatic fibrosis is likely to be substantially lower.

CONCLUSIONS

Although the detection rate from testing the families of unaffected heterozygotes is low, this can be justified as a clinically useful screening strategy. At the present time this strategy should be restricted to first-degree relatives of heterozygotes. Further studies are recommended to determine if cascade genetic screening is a cost-effective alternative to general population screening.