Efficacy of statewide neonatal screening for cystic fibrosis by assay of trypsinogen concentrations

Update on advances in cystic fibrosis towards a cure and implications for primary care clinicians

During the past quarter century, the diagnosis and treatment of cystic fibrosis (CF) have been transformed by molecular sciences that initiated a new era with discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The knowledge gained from that breakthrough has had dramatic clinical impact. Although once a diagnostic dilemma with long delays, preventable deaths, and irreversible pathology, CF can now be routinely diagnosed shortly after birth through newborn screening programs. This strategy of pre-symptomatic identification has eliminated the common diagnostic "odyssey" that was a failure of the healthcare delivery system causing psychologically traumatic experiences for parents. Therapeutic advances of many kinds have culminated in CFTR modulator treatment that can reduce the effects of or even correct the molecular defect in the chloride channel -the basic cause of CF. This astonishing advance has transformed CF care as described fully herein. Despite this impressive progress, there are challenges and controversies in the delivery of care. Issues include how best to achieve high sensitivity newborn screening with acceptable specificity; what course of action is appropriate for children who are identified through the unavoidable incidental findings of screening tests (CFSPID/CRMS cases and heterozygote carriers); how best to ensure genetic counseling; when to initiate the very expensive but life-saving CFTR modulator drugs; how to identify new CFTR modulator drugs for patients with non-responsive CFTR variants; how to adjust other therapeutic modalities; and how to best partner with primary care clinicians. Progress always brings new challenges, and this has been evident worldwide for CF. Consequently, this article summarizes the major advances of recent years along with controversies and describes their implications with an international perspective.

Newborn Screening in Developing Countries: The Need of the Hour

Screening newborns is recognized as an important health policy. It is cost-effective and is implemented as a national health program in most developed countries. Though births in developing countries contribute to more than half of the total births globally, newborn screening (NBS) is not yet implemented in most developing countries. If not diagnosed and treated timely, some of these infants will contribute to neonatal mortality. In contrast, others will have long-term sequelae like developmental delay, learning disabilities, behavioral abnormalities, and backward academic performance in the future. In addition, the diagnosis, management, and treatment of these conditions also carry a significant financial as well as emotional burden on the family. An NBS program can be the most rational and effective way to prevent such morbidities and mortalities. NBS in developing countries competes with other health issues such as the control of infectious diseases, vaccinations, and poor nutrition. Also, lack of government support, poor economy, inadequate public health education, lack of awareness among health care workers, early discharge from hospital, and many births out of hospital are the significant obstacles in the countries that lack total coverage. It is high time now to change our attitude; our focus should be not only on the reduction of mortality and infectious morbidity but also on reducing disabilities with the introduction of screening for newborns. Integrating NBS with the national healthcare system is crucial for successful implementation in developing countries. Integration should also include a payment scheme to reduce the economic burden on families. In recent years, many developing countries have started implementing pilot projects as a step toward the national program of screening newborns.

Severe lung disease in children with cystic fibrosis missed in newborn screening

BACKGROUND

Cystic fibrosis (CF) is now routinely diagnosed through newborn screening (NBS), but the tests employed in the USA have been evolving for two decades as missed cases become recognized and lab methods improve in association with more knowledge about CF genetics. New Jersey was among the first states to implement CF NBS in 2001 when it introduced the original two-tiered method that combined measurements of immunoreactive trypsinogen (IRT) with detection of the principal pathogenic variant (F508del) in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.

OBJECTIVE

With continuation of the IRT/DNA (F508del) algorithm for two decades and identification of screening false negative children, we decided to examine the condition of some missed cases with special attention to their respiratory status.

METHODS

To strengthen the arguments for quality improvement in New Jersey's CF NBS program, we reviewed and evaluated false negative cases to determine the potential extent of preventable patient suffering as a consequence of delayed diagnoses.

RESULTS

Five children with CF who had false negative screening results were studied in detail. In each case there was a different cause of the negative screening results. They all had clinically significant/severe lung disease, ranging from chronic cough with CF pathogens on respiratory culture at a young age to respiratory failure.

CONCLUSION

This case series highlights the consequences of false negative screening results, which served as the impetus to upgrade New Jersey's CF NBS algorithm. Implemented changes include lowering the IRT cutoff to 70 ng/mL and expanding to a 139 variant CFTR panel. In 2023, a floating IRT cutoff is anticipated to be implemented.

False negatives in the newborn screening for cystic fibrosis in Western Andalusia: Results from a 10-year experience

Cystic fibrosis (CF) is the most common autosomal recessive disorder in the Caucasian population, with an incidence of 1:5000 live births. In 2011, the screening of CF was implemented in the Andalusian Public Health newborn screening program by using immunoreactive trypsinogen and chloride sweat test (IRT/IRT/sweat test) determinations. Since then, 79 children have been diagnosed with CF in our health area (Western Andalusia). The aim of this study was to evaluate the efficiency of this screening method and to examinate the characteristics of those CF infants who had a negative screening but who were later diagnosed. In the 2011-2021 period 462,049 newborns were screened for CF using a two-step IRT determination and chloride sweat test. Sixty-three infants were diagnosed with CF in our health area thanks to the screening, and 15 CF children had a negative screening result and were finally diagnosed by molecular sequencing of the CFTR gene. The most frequent symptoms that led to the diagnosis of those false negative (FN) patients were hyponatremic dehydration (mean age 9.75 ± 1.5 months) and recurrent wheezing (mean age 24 ± 14.5 months). The molecular analysis of the CFTR gene on those FN showed a diversity of genotypes, identifying more than 10 different mutations. CONCLUSION: The rate of FN patients obtained in this study is inadmissibly high, and the protocol used in this region has not been updated despite the advances in genetic testing in the past 10 years. An improvement on CF newborn screening should be implemented, adding molecular analysis of the CFTR gene.

Why cystic fibrosis newborn screening programs have failed to meet original expectations… thus far

This Commentary summarizes what the author has learned in 46 years of research on newborn screening (NBS) for cystic fibrosis (CF) combined with healthcare and public health practice. The original expectation was that screening for this relatively common, life-threatening genetic disorder would lead to consistently timely diagnoses in the neonatal period and be equitable. Unfortunately, this ambitious goal has not been achieved in the USA despite the availability of an excellent, although imperfect, 2-tiered screening test employing immunoreactive trypsinogen (IRT) and DNA analysis for pathogenic variants in the gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR). In fact, variations in the quality of NBS programs, inconsistencies in their operations, and disparities in outcomes have been prominent features. The causes include leadership challenges and deficiencies among both CF centers and NBS labs; failures to form effective partnerships among CF centers and with NBS programs; relatively rapid implementation after 2005 with variable quality planning; misunderstandings and erroneous dogma about CF; data limitations regarding IRT, especially cutoff values, and CFTR genetics; tolerance of suboptimal protocols and false negative results; problems in dried blood spot collections plus a lack of transparency and national oversight; partial lack of readiness, qualifications, funding and/or willingness to innovate with floating IRT cutoffs and DNA/CFTR analyses; follow up challenges/deficiencies impairing timeliness, including sweat testing limitations; and published guidelines that are more descriptive than sufficiently critical and directive. But the lessons learned through uniquely intensive CF NBS research have been enlightening and guided the U.S. Cystic Fibrosis Foundation to nationwide quality improvement initiatives.

Diagnostic and Communication Challenges in Cystic Fibrosis Newborn Screening

As of December 2009, cystic fibrosis (CF) newborn screening (NBS) is performed in all 50 US states and the District of Columbia. Widespread implementation of CF newborn screening (CFNBS) in the US and internationally has brought about new and varied challenges. Immunoreactive trypsinogen (IRT) remains the first, albeit imperfect, biomarker used universally in the screening process. Advances in genetic testing have provided an opportunity for newborn screening programs to add CFTR sequencing tiers to their algorithms. This in turn will enable earlier identification of babies with CF and improve longer-term outcomes through prompt treatment and intervention. CFTR sequencing has led to the ability to identify infants with CF from diverse ethnic and racial backgrounds more equitably while also identifying an increasing proportion of infants with inconclusive diagnoses. Using the evolution of the New York State CF newborn screening program as a guide, this review outlines the basic steps in a universal CF newborn screening program, considers how to reduce bias, highlights challenges, offers guidance to address these challenges and provides recommendations for future consideration.

Refinement of newborn screening for cystic fibrosis with next generation sequencing

BACKGROUND

Newborn screening for cystic fibrosis (CF) has been underway universally in the United States for more than a decade, as well in most European countries, and algorithms have been evolving throughout this period with quality improvement projects as immunoreactive trypsinogen (IRT) determinations alone have been transformed to a 2-tier strategy with DNA analyses.

OBJECTIVE

To apply next generation sequencing (NGS) as a screening method to expand the DNA tier and identify substantially more variants in the CF transmembrane conductance regulator (CFTR) gene to enhance sensitivity and equity while minimizing incidental findings.

DESIGN

Sequential evaluation and improvement plan in three phases using algorithm modifications coupled to statewide follow up and analysis of screening outcomes.

RESULTS

After demonstrating feasibility in the first phase, we studied an IRT/NGS algorithm that included CFTR Variants with Varying Clinical Consequences (VVCCs). This revealed a high identification of CF patients with 2-variants detected through screening, but for every CF case there were 1.4 with CF metabolic syndrome/CF screen positive, inconclusive diagnosis (CRMS/CFSPID). This led us to a third phase of improvement in which the VVCCs were eliminated except for R117H, resulting in 94% 2-variant detection of patients and 0.44:1 ratio of CRMS/CFSPID to CF.

CONCLUSION

NGS can be used with IRT as an effective method of identifying infants at risk for CF without an appreciable increase in detection of carriers. Its potential added value includes facilitating equity, enhancing sensitivity and detecting more CF patients with 2-variants during the screening process.

Parental Preferences about Policy Options Regarding Disclosure of Incidental Genetic Findings in Newborn Screening: Using Videos and the Internet to Educate and Obtain Input

Our objective was to develop and test a new approach to obtaining parental policy guidance about disclosure of incidental findings of newborn screening for cystic fibrosis (CF), including heterozygote carrier status and the conditions known as CFTR-related metabolic syndrome (CRMS) and/or cystic fibrosis screen positive inconclusive diagnosis, CFSPID. The participants were parents of infants up to 6 months old recruited from maternity hospitals/clinics, parent education classes and stores selling baby products. Data were collected using an anonymous, one-time Internet-based survey. The survey introduced two scenarios using novel, animated videos. Parents were asked to rank three potential disclosure policies-Fully Informed, Parents Decide, and Withholding Information. Regarding disclosure of information about Mild X (analogous to CRMS/CFSPID), 57% of respondents ranked Parents Decide as their top choice, while another 41% ranked the Fully Informed policy first. Similarly, when considering disclosure of information about Disease X (CF) carrier status, 50% and 43% gave top rankings to the Fully Informed and Parents Decide policies, respectively. Less than 8% ranked the Withholding Information policy first in either scenario. Data from value comparisons suggested that parents believed knowing everything was very important even if they became distressed. Likewise, parents preferred autonomy even if they became distressed. However, when there might not be enough time to learn everything, parents showed a slight preference for deferring decision-making. Because most parents strongly preferred the policies of full disclosure or making the decision, rather than the withholding option for NBS results, these results can inform disclosure policies in NBS programs, especially as next-generation sequencing increases incidental findings.

Improving outcomes for Colorado's IRT-IRT-DNA cystic fibrosis newborn screening algorithm by implementing floating cutoffs

The Colorado Newborn Screening Program (CO-NBS) screens for cystic fibrosis (CF) by measuring immunoreactive trypsinogen (IRT) from two screens coupled with DNA analysis (IRT/IRT/DNA). The Colorado CF Care Center identified 8 missed CF cases among 358,187 infants screened by the CO-NSP since 2016. Retrospective analysis of CO-NSP IRT data shows that a 96th percentile floating IRT cutoff with a 50 ng/mL fixed cutoff on the first screen, and second screen 50 ng/mL fixed cutoff would have identified 7 of the 8 missed cases. These efforts demonstrate the importance of continuous quality improvement in order to increase sensitivity and reduce missed cases.

Dehydrated patient without clinically evident cause: A case report

BACKGROUND

Patients affected by cystic fibrosis can present with metabolic alkalosis such as Bartter’s syndrome. In this case report we want to underline this differential diagnosis and we aimed focusing on the suspect of cystic fibrosis, also in case of a negative newborn screening.

CASE SUMMARY

In a hot August –with a mean environmental temperature of 36 °C– an 8-mo-old female patient presented with severe dehydration complicated by hypokalemic metabolic alkalosis, in absence of fever, diarrhea and vomiting. Differential diagnosis between cystic fibrosis and tubulopathies causing metabolic alkalosis (Bartter’s Syndrome) was considered. We started intravenous rehydration with subsequent improvement of clinical conditions and serum electrolytes normalization. We diagnosed a mild form of cystic fibrosis (heterozygous mutations: G126D and F508del in the cystic fibrosis transmembrane conductance regulator gene). The trigger factor of this condition had been heat exposure.

CONCLUSION

When facing a patient with hypokalemic metabolic alkalosis, cystic fibrosis presenting with Pseudo-Bartter’s syndrome should be considered in the differential diagnosis, even if the newborn screening was negative.

Constructing a Bioethical Framework to Evaluate and Optimise Newborn Bloodspot Screening for Cystic Fibrosis

Newborn bloodspot screening for cystic fibrosis is a valid public health strategy for populations with a high incidence of this inherited condition. There are a wide variety of approaches to screening and in this paper, we propose that a bioethical framework is required to determine the most appropriate screening protocol for a population. This framework depends on the detailed evaluation of the ethical consequences of all screening outcomes and placing these in the context of the genetic profile of the population screened, the geography of the region and the healthcare resources available.

A model-based economic evaluation of four newborn screening strategies for cystic fibrosis in Flanders, Belgium

Objectives: The most cost-effective newborn screening strategy for cystic fibrosis (CF) for Flanders, Belgium, is unknown. The aim of this study was to assess the cost-effectiveness of four existing newborn screening strategies for CF: IRT-DNA (immunoreactive trypsinogen, cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation analysis), IRT-PAP (pancreatitis-associated protein), IRT-PAP-DNA, and IRT-PAP-DNA-EGA (extended CFTR gene analysis).Methods: Using data from published literature, the cost-effectiveness of the screening strategies was calculated for a hypothetical cohort of 65,606 newborns in Flanders, Belgium. A healthcare payer perspective was used, and the direct medical costs associated with screening were taken into account. The robustness of the model outcomes was assessed in sensitivity analyses.Results: The IRT-PAP strategy was the most cost-effective strategy in terms of costs per CF case detected (€9314 per CF case detected). The IRT-DNA strategy was more costly (€13,966 per CF case detected), but with an expected sensitivity of 93.4% also the most effective strategy, and was expected to detect 2.2 more cases of CF than the IRT-PAP strategy. The incremental cost-effectiveness ratio of IRT-DNA vs. IRT-PAP was €54,180/extra CF case detected. The IRT-PAP-DNA strategy and the IRT-PAP-DNA-EGA strategy were both strongly dominated by the IRT-PAP strategy.Conclusion: The IRT-PAP strategy was the most cost-effective strategy in terms of costs per CF case detected. However, the strategy did not fulfil the European Cystic Fibrosis Society guidelines for sensitivity and positive predictive value. Therefore, the more costly and more effective IRT-DNA strategy may be the most appropriate newborn screening strategy for Flanders.

The Impact of the CFTR Gene Discovery on Cystic Fibrosis Diagnosis, Counseling, and Preventive Therapy

Discovery of the cystic fibrosis transmembrane conductance regulator (CFTR) gene was the long-awaited scientific advance that dramatically improved the diagnosis and treatment of cystic fibrosis (CF). The combination of a first-tier biomarker, immunoreactive trypsinogen (IRT), and, if high, DNA analysis for CF-causing variants, has enabled regions where CF is prevalent to screen neonates and achieve diagnoses within 1-2 weeks of birth when most patients are asymptomatic. In addition, IRT/DNA (CFTR) screening protocols simultaneously contribute important genetic data to determine genotype, prognosticate, and plan preventive therapies such as CFTR modulator selection. As the genomics era proceeds with affordable biotechnologies, the potential added value of whole genome sequencing will probably enhance personalized, precision care that can begin during infancy. Issues remain, however, about the optimal size of CFTR panels in genetically diverse regions and how best to deal with incidental findings. Because prospects for a primary DNA screening test are on the horizon, the debate about detecting heterozygote carriers will likely intensify, especially as we learn more about this relatively common genotype. Perhaps, at that time, concerns about CF heterozygote carrier detection will subside, and it will become recognized as beneficial. We share new perspectives on that issue in this article.

Newborn Screening Saves Lives but Cannot Replace the Need for Clinical Vigilance

Newborn screening for cystic fibrosis (CF) enables early diagnosis and treatment leading to improved health outcomes for patients with CF. Although the sensitivity of newborn screening is high, false-negative results can still occur which can be misleading if clinicians are not aware of the clinical presentation of CF. We present a case of a young male with negative newborn screen diagnosed for CF. He was diagnosed at 3 years of age despite having symptoms indicative of CF since infancy. The delayed diagnosis resulted in diffuse lung damage and poor growth.

Case Definitions for Conditions Identified by Newborn Screening Public Health Surveillance

Newborn screening (NBS) identifies infants with rare conditions to prevent death or the onset of irreversible morbidities. Conditions on the Health and Human Services Secretary's Recommended Uniform Screening Panel have been adopted by most state NBS programs, providing a consistent approach for identification of affected newborns across the United States. Screen-positive newborns are identified and referred for confirmatory diagnosis and follow-up. The designation of a clinically significant phenotype precursor to a clinical diagnosis may vary between clinical specialists, resulting in diagnostic variation. Determination of disease burden and birth prevalence of the screened conditions by public health tracking is made challenging by these variations. This report describes the development of a core group of new case definitions, along with implications, plans for their use, and links to the definitions that were developed by panels of clinical experts. These definitions have been developed through an iterative process and are piloted in NBS programs. Consensus public health surveillance case definitions for newborn screened disorders will allow for consistent categorization and tracking of short- and long-term follow-up of identified newborns at the local, regional, and national levels.

Early childhood lung function is a stronger predictor of adolescent lung function in cystic fibrosis than early Pseudomonas aeruginosa infection

OBJECTIVE

Pseudomonas aeruginosa has been suggested as a major determinant of poor pulmonary outcomes in cystic fibrosis (CF), although other factors play a role. Our objective was to investigate the association of early childhood Pseudomonas infection on differences in lung function in adolescence with CF.

METHODS

Two populations of subjects with CF were studied: from the Gene Modifier Study (GMS), 346 F508del homozygotes with severe vs. mild adolescent lung disease, and from the Colorado Newborn Screen Study (NBS) 172 subjects diagnosed with CF by newborn screening. Associations of Pseudomonas infection and lung function in early childhood with lung function in adolescence were investigated using multivariate linear regression analyses.

RESULTS

Among GMS subjects, those with severe adolescent lung disease had worse lung function in childhood (FEV1 25 percentage points lower) compared to subjects with mild adolescent lung disease, regardless of early childhood Pseudomonas status. Among NBS subjects, those with lowest adolescent lung function had significantly lower early childhood lung function and faster rate of decline in FEV1 than subjects with highest adolescent lung function; early Pseudomonas infection was not associated with rate of FEV1 decline. The strongest predictor of adolescent lung function was early childhood lung function. Subjects with a higher percentage of cultures positive for Pseudomonas before age 6 or a lower BMI at 2-4 years old also had lower adolescent lung function, though these associations were not as strong as with early childhood lung function.

CONCLUSIONS

In separate analyses of two distinct populations of subjects with CF, we found a strong correlation between lower lung function in early childhood and adolescence, regardless of early childhood Pseudomonas status. Factors in addition to early Pseudomonas infection have a strong impact on lung function in early childhood in CF. Further exploration may identify novel underlying genetic or environmental factors that predispose children with CF to early loss of lung function.

Improving the Sensitivity and Positive Predictive Value in a Cystic Fibrosis Newborn Screening Program Using a Repeat Immunoreactive Trypsinogen and Genetic Analysis

OBJECTIVE

To evaluate the performance of a new cystic fibrosis (CF) newborn screening algorithm, comprised of immunoreactive trypsinogen (IRT) in first (24-48 hours of life) and second (7-14 days of life) dried blood spot plus DNA on second dried blood spot, over existing algorithms.

STUDY DESIGN

A retrospective review of the IRT/IRT/DNA algorithm implemented in Colorado, Wyoming, and Texas.

RESULTS

A total of 1 520 079 newborns were screened, 32 557 (2.1%) had abnormal first IRT; 8794 (0.54%) on second. Furthermore, 14 653 mutation analyses were performed; 1391 newborns were referred for diagnostic testing; 274 newborns were diagnosed; and 201/274 (73%) of newborns had 2 mutations on the newborn screening CFTR panel. Sensitivity was 96.2%, compared with sensitivity of 76.1% observed with IRT/IRT (105 ng/mL cut-offs, P < .0001). The ratio of newborns with CF to heterozygote carriers was 1:2.5, and newborns with CF to newborns with CFTR-related metabolic syndrome was 10.8:1. The overall positive predictive value was 20%. The median age of diagnosis was 28, 30, and 39.5 days in the 3 states.

CONCLUSIONS

IRT/IRT/DNA is more sensitive than IRT/IRT because of lower cut-offs (∼97 percentile or 60 ng/mL); higher cut-offs in IRT/IRT programs (>99 percentile, 105 ng/mL) would not achieve sufficient sensitivity. Carrier identification and identification of newborns with CFTR-related metabolic syndrome is less common in IRT/IRT/DNA compared with IRT/DNA. The time to diagnosis is nominally longer, but diagnosis can be achieved in the neonatal period and opportunities to further improve timeliness have been enacted. IRT/IRT/DNA algorithm should be considered by programs with 2 routine screens.

Cystic Fibrosis Diagnosis and Newborn Screening

The diagnosis of cystic fibrosis (CF) has evolved over the past decade as newborn screening has become universal in the United States and elsewhere. The heterogeneity of phenotypes associated with CF transmembrane conductance regulator (CFTR) dysfunction and mutations in the CFTR gene has become clearer, ranging from classic pancreatic-insufficient CF to manifestations in only 1 organ system to indeterminate diagnoses identified by newborn screening. The tools available for diagnosis have also expanded. This article reviews the newest diagnostic criteria for CF, newborn screening, prenatal screening and diagnosis, and indeterminate diagnoses in newborn-screened infants and symptomatic adults.

Newborn Screening Quality Assurance Program for CFTR Mutation Detection and Gene Sequencing to Identify Cystic Fibrosis

All newborn screening laboratories in the United States and many worldwide screen for cystic fibrosis. Most laboratories use a second-tier genotyping assay to identify a panel of mutations in the CF transmembrane regulator (CFTR) gene. Centers for Disease Control and Prevention’s Newborn Screening Quality Assurance Program houses a dried blood spot repository of samples containing CFTR mutations to assist newborn screening laboratories and ensure high-quality mutation detection in a high-throughput environment. Recently, CFTR mutation detection has increased in complexity with expanded genotyping panels and gene sequencing. To accommodate the growing quality assurance needs, the repository samples were characterized with several multiplex genotyping methods, Sanger sequencing, and 3 next-generation sequencing assays using a high-throughput, low-concentration DNA extraction method. The samples performed well in all of the assays, providing newborn screening laboratories with a resource for complex CFTR mutation detection and next-generation sequencing as they transition to new methods.

Diagnostic Testing in Cystic Fibrosis

Cystic Fibrosis (CF) is a rare, multisystem disease leading to significant morbidity and mortality. CF is caused by defects in the cystic fibrosis transmembrane conductance regulator protein (CFTR), a chloride and bicarbonate transporter. Early diagnosis and access to therapies provides benefits in nutrition, pulmonary health, and cognitive ability. Several screening and diagnostic tests are available to support a diagnosis. We discuss the characteristics of screening and diagnostic tests for CF and guideline-based algorithms using these tools to establish a diagnosis. We discuss classification and management of common "diagnostic dilemmas," including the CFTR-related metabolic syndrome and other CFTR-associated diseases.

Advances in the diagnosis and treatment of cystic fibrosis

CF is a genetic, life-shortening, multisystem disease that is most commonly diagnosed through newborn screen performed in all 50 states in the United States. In the past, therapies for CF lung disease have primarily targeted the downstream effects of a dysfunctional CFTR protein. Newer CFTR modulator therapies, targeting the basic defect in CF, are available for a limited group of people with CF, and offer the hope of improved treatment options for many more people with CF in the near future. Best practice is directed by consensus clinical care guidelines from the CFF and is provided with a multidisciplinary approach by the team at the CF care center and the primary care office.

The evolution of blood-spot newborn screening

Over 50 years after the introduction of a blood-spot newborn screening test using the bacterial-inhibition assay (BIA), blood-spot newborn screening has evolved into complex public service scientific programmes. For several decades, many patients with phenylketonuria (PKU), congenital hypothyroidism (CH), cystic fibrosis (CF) and hemoglobinopathy disorders have benefited from early intervention across the world. In the last 20 years, there have been great changes in laboratory techniques and high-throughput data handling meaning that a huge spectrum of disorders can be identified from an increasing population. This coupled with the fact that there are an increasing number of therapies for specific rare disorders mean that health services may become inundated with complex and expensive demands in the future. Some of these issues have been realised in the implementation of multiplex assay such as electrospray tandem mass spectrometry (MSMS) programmes but will be much more exaggerated if genomic sequencing screening becomes a reality. In this context, the core-principles for implementation of newborn screening tests remain as important today as they have in the past when new tests are considered as part of the blood-spot screening programme.

Invasive pneumonia and septic shock in infants as a presentation of cystic fibrosis with vitamin-deficiency

Herein we describe three infants with the rare presentation of pneumonia with septic shock as their initial medical encounter leading to the diagnosis of cystic fibrosis (CF). At the time of their presentation all three children had significant nutritional deficiency. We initiated an aggressive treatment regimen including nutritional supplementation which resulted in improvement in their pulmonary status and no further recurrences. This series highlights the possible presentation of CF in infancy as a life-threatening invasive infection of Staphylococcus aureus or Pseudomonas aeruginosa. It also supports neonatal screening and emphasizes the role of early attention to nutritional status and vitamin supplementation.

Aquagenic wrinkling of the palms and the potential role for genetic testing

Aquagenic wrinkling of the palms (AWP) is a condition characterized by excessive wrinkling, palmar edema, and whitish papules accompanied by pain, pruritus, or discomfort after brief immersion of the hands in water. It is well documented to be associated with cystic fibrosis (CF), with several theories regarding the pathogenesis having been proposed. We report a case of two sisters with AWP in whom CF has not been diagnosed and review the literature on AWP and its association with CF and CF carrier status. Because diagnosis of mild forms CF or knowledge of an underlying CF genetic mutation is frequently unknown, identification of AWP may represent the only sign of such mutations. The dermatologist plays an integral role in early detection of AWP, and the importance of genetic testing in such patients cannot be overlooked. We recommend various measures to apply in clinical practice to ensure diagnosis and decrease morbidity and mortality in patients.

Immunoreactive Trypsinogen (IRT) as a Biomarker for Cystic Fibrosis: challenges in newborn dried blood spot screening

On May 23-24, 2011, a workshop entitled "Immunoreactive Trypsinogen (IRT) as a Biomarker for Cystic Fibrosis: Technical Issues and Challenges" was held in Annapolis, Maryland. The two-day workshop was co-hosted by the National Newborn Screening and Genetics Resource Center, Austin, Texas, and the Association of Public Health Laboratories, Silver Spring, Maryland, in collaboration with the Health Resources and Services Administration and the Centers for Disease Control and Prevention. Participants included nearly 40 representatives from U.S. state public health and commercial laboratories performing newborn dried blood spot screening tests for cystic fibrosis (CF), the federal government, academic research institutions, and commercial vendors of products used in newborn screening. Representatives from selected European CF newborn screening programs were also present. The workshop focused on identifying key IRT testing issues and mechanisms for achieving their resolution and laboratory harmonization in order to reduce, or eliminate completely, the late identified CF cases following a negative newborn screen. Informative findings are reported, their impacts on improving IRT screening are described, and their implications are discussed.

A decision-tree approach to cost comparison of newborn screening strategies for cystic fibrosis

OBJECTIVE

Because cystic fibrosis can be difficult to diagnose and treat early, newborn screening programs have rapidly developed nationwide but methods vary widely. We therefore investigated the costs and consequences or specific outcomes of the 2 most commonly used methods.

METHODS

With available data on screening and follow-up, we used a simulation approach with decision trees to compare immunoreactive trypsinogen (IRT) screening followed by a second IRT test against an IRT/DNA analysis. By using a Monte Carlo simulation program, variation in the model parameters for counts at various nodes of the decision trees, as well as for costs, are included and applied to fictional cohorts of 100 000 newborns. The outcome measures included the numbers of newborns given a diagnosis of cystic fibrosis and costs of screening strategy at each branch and cost per newborn.

RESULTS

Simulations revealed a substantial number of potential missed diagnoses for the IRT/IRT system versus IRT/DNA. Although the IRT/IRT strategy with commonly used cutoff values offers an average overall cost savings of $2.30 per newborn, a breakdown of costs by societal segments demonstrated higher out-of-pocket costs for families. Two potential system failures causing delayed diagnoses were identified relating to the screening protocols and the follow-up system.

CONCLUSIONS

The IRT/IRT screening algorithm reduces the costs to laboratories and insurance companies but has more system failures. IRT/DNA offers other advantages, including fewer delayed diagnoses and lower out-of-pocket costs to families.

CFTR mutation analysis and haplotype associations in CF patients

Most newborn screening (NBS) laboratories use second-tier molecular tests for cystic fibrosis (CF) using dried blood spots (DBS). The Centers for Disease Control and Prevention's NBS Quality Assurance Program offers proficiency testing (PT) in DBS for CF transmembrane conductance regulator (CFTR) gene mutation detection. Extensive molecular characterization on 76 CF patients, family members or screen positive newborns was performed for quality assurance. The coding, regulatory regions and portions of all introns were sequenced and large insertions/deletions were characterized as well as two intronic di-nucleotide microsatellites. For CF patient samples, at least two mutations were identified/verified and four specimens contained three likely CF-associated mutations. Thirty-four sequence variations in 152 chromosomes were identified, five of which were not previously reported. Twenty-seven of these variants were used to predict haplotypes from the major haplotype block defined by HapMap data that spans the promoter through intron 19. Chromosomes containing the F508del (p.Phe508del), G542X (p.Gly542X) and N1303K (p.Asn1303Lys) mutations shared a common haplotype subgroup, consistent with a common ancient European founder. Understanding the haplotype background of CF-associated mutations in the U.S. population provides a framework for future phenotype/genotype studies and will assist in determining a likely cis/trans phase of the mutations without need for parent studies.

Factors accounting for a missed diagnosis of cystic fibrosis after newborn screening

Newborn screening is a public health policy program involving the centralized testing laboratory, infant and their family, primary care provider, and subspecialist for confirmatory testing and follow-up of abnormal results. Cystic fibrosis (CF) newborn screening has now been enacted in all 50 states and the District of Columbia and throughout many countries in the world. Although CF neonatal screening will identify the vast majority of infants with CF, there are many factors in the newborn screening system that can lead to a missed diagnosis of CF. To inform clinicians, this article summarizes the CF newborn screening system and highlights 14 factors that can account for a missed diagnosis of CF. Care providers should maintain a high suspicion for CF if there are compatible symptoms, regardless of the results of the newborn screening test. These factors in newborn screening programs leading to a missed diagnosis of CF present opportunities for quality improvement in specimen collection, laboratory analysis of immunoreactive tryspinogen (IRT) and CF mutation testing, communication, and sweat testing.

Comparing age of cystic fibrosis diagnosis and treatment initiation after newborn screening with two common strategies

BACKGROUND

Newborn screening (NBS) for CF has become widespread, although there are multiple strategies. Little is known about outcomes such as age of diagnosis after different NBS methods.

METHODS

We used the U.S. Cystic Fibrosis Foundation Patient Registry to identify infants with CF born between 2001 and 2008 in states that utilized NBS. We compared ages at diagnosis, genotyping, sweat test, and first visit to a CF Centre between states that used serial immunoreactive trypsinogen (IRT/IRT) levels and states that used IRT and DNA analysis (IRT/DNA).

RESULTS

We identified 1288 infants with CF. Compared to infants born in IRT/IRT states, infants born in IRT/DNA states were younger at the time of diagnosis (median 2.3 weeks versus 4.0 weeks in IRT/IRT states, p<0.001), genotyping (0.7 weeks versus 5.3 weeks, p<0.001), and initial CF Centre visit (5.9 weeks versus 7.7 weeks, p=0.008).

CONCLUSIONS

Although there is room to improve outcomes with both strategies, infants born in IRT/DNA states have treatment initiated at a younger age than infants born in IRT/IRT states.

The need for vigilance: the case of a false-negative newborn screen for cystic fibrosis

Cystic fibrosis (CF) is the most common life-limiting recessive genetic disorder in the white population. CF is caused by abnormalities in the gene that codes for the cystic fibrosis transmembrane conductance regulator protein (CFTR) and may result in severe chronic lung disease, poor growth, and malnutrition. Physicians often do not consider CF in the differential diagnosis of an infant with failure to thrive in the presence of a negative newborn screening (NBS) result. In Minnesota, newborn infants are screened for CF by immunoreactive trypsinogen (IRT) testing followed by DNA analysis if the IRT screen result is abnormal. All positive NBS results are followed by confirmatory sweat-testing by pilocarpine iontophoresis. We present here the case of a 1-month-old white boy with failure to thrive, chronic diarrhea, and severe malnutrition. Minnesota state CF NBS results were negative at birth (IRT: 43 ng/mL [96% cutoff value: 52 ng/mL]). Clinical symptoms resulted in sweat-testing by Gibson-Cooke pilocarpine iontophoresis at 1 month of age, and the result was positive (102 mmol Cl(-)/L [normal: ≤30 mmol Cl(-)/L]). CFTR mutation analysis confirmed a homozygous f508del genotype, and stool pancreatic elastase testing revealed severe exocrine pancreatic insufficiency. This case represents the first known false-negative result in Minnesota since the initiation of NBS for CF in 2006, which illustrates the importance of considering CF in the evaluation of an infant with failure to thrive and symptoms of malabsorption, regardless of NBS results.

Growth and pulmonary outcomes during the first 2 y of life of breastfed and formula-fed infants diagnosed with cystic fibrosis through the Wisconsin Routine Newborn Screening Program

BACKGROUND

The optimal feeding (breast milk, formula, or a combination) for infants with cystic fibrosis (CF) is unknown. Recommendations from the CF Foundation are based on limited data.

OBJECTIVE

We compared growth and pulmonary outcomes between breastfed and formula-fed infants through the age of 2 y.

DESIGN

A total of 103 CF infants born in 1994-2006 and diagnosed through newborn screening in Wisconsin were studied. Breastfed infants were classified by the duration of exclusive breastfeeding (ExBF). Exclusive formula-feeding (ExFM) was classified by the formula's caloric density (ie, standard [0.67 kcal/mL (20 kcal/oz) (ExFM20)] throughout infancy or high density [≥0.74 kcal/mL (22 kcal/oz) (ExFM22+)] for some duration of infancy).

RESULTS

Fifty-three infants (51% of infants) were breastfed and 50 infants (49% of infants) were ExFM. In breastfed infants, the duration of ExBF was <1 mo (53% of infants), 1-1.9 mo (21% of infants), 2-3 mo (17% of infants), and 4-9 mo (9% of infants). In ExFM infants, 23 infants (46%) received a formula with a high caloric density; approximately half (n = 13) of the ExFM infants received the formula by 6 mo of age. Proportionately more infants with pancreatic sufficiency (n = 9) were ExBF ≥1 mo (44% of infants), and none of the infants were ExFM22+, compared with infants with meconium ileus (n = 24; 13% of infants were ExBF ≥1 mo, and 38% of infants were ExFM22+) or pancreatic insufficiency (n = 70; 25% of infants were ExBF ≥1 mo, and 20% of infants were ExFM22+) (P = 0.02). In infants with pancreatic insufficiency, weight z scores declined from birth to 6 mo (P < 0.0001) in infants who were ExBF ≥2 mo, and the number of Pseudomonas aeruginosa infections through the age of 2 y was fewer in breastfed than in ExFM infants (P = 0.003) but did not differ by the duration of ExBF.

CONCLUSION

For infants with CF, ExBF <2 mo does not compromise growth and is associated with a respiratory benefit.

Optimal DNA tier for the IRT/DNA algorithm determined by CFTR mutation results over 14 years of newborn screening

BACKGROUND

There has been great variation and uncertainty about how many and what CFTR mutations to include in cystic fibrosis (CF) newborn screening algorithms, and very little research on this topic using large populations of newborns.

METHODS

We reviewed Wisconsin screening results for 1994-2008 to identify an ideal panel.

RESULTS

Upon analyzing approximately 1 million screening results, we found it optimal to use a 23 CFTR mutation panel as a second tier when an immunoreactive trypsinogen (IRT)/DNA algorithm was applied for CF screening. This panel in association with a 96th percentile IRT cutoff gave a sensitivity of 97.3%, but restricting the DNA tier to F508del was associated with 90% (P<.0001).

CONCLUSIONS

Although CFTR panel selection has been challenging, our data show that a 23 mutation method optimizes sensitivity and is advantageous. The IRT cutoff value, however, is actually more critical than DNA in determining CF newborn screening sensitivity.

Parental understanding of newborn screening for cystic fibrosis after a negative sweat-test

BACKGROUND

Newborn screening for cystic fibrosis (CF) in Illinois uses an immunoreactive trypsinogen/DNA methodology; most false-positive results identify unaffected carriers.

METHODS

Parents whose child received a negative result from the sweat test after a positive newborn screening for CF were surveyed ≥ 6 weeks later by telephone. All parents received genetic counseling while waiting for the sweat-test results.

RESULTS

A total of 90 parents participated. Overall knowledge of CF was high (78%), but the ability to understand the CF screening results was mixed. Although 94% of the parents understood that their child did not have CF, only 79% (62 of 78) of participants whose child had a mutation knew their child was definitely a carrier, and only 1 of 12 parents whose child had no mutation understood that the child may be a carrier. Respondents stated that most relatives were not interested in genetic testing. Both parents had been tested in only 13 couples. Fewer than half (36 of 77 [47%]) of the untested couples expressed interest in genetic testing. Although most participants were satisfied with the process, parents expressed frustration because of the lack of prospective newborn screening discussions by prenatal and pediatric providers and lack of knowledge and sensitivity by those who initially notified them of the abnormal newborn screening results. Speaking to a genetic counselor when scheduling the sweat test decreased anxiety for many parents (53 of 73 [73%] were "very worried" at notification versus 18 of 73 [25%] after scheduling; P < .001).

CONCLUSIONS

Parental knowledge about CF is high, but confusion about the child's carrier status and the concept of residual risk persist despite genetic counseling. Relatives express low interest in carrier testing.

A new cystic fibrosis newborn screening algorithm: IRT/IRT1 upward arrow/DNA

OBJECTIVE

To evaluate an immunoreactive trypsinogen (IRT) IRT/IRT1 upward arrow/DNA algorithm, aimed at improving sensitivity while decreasing cystic fibrosis (CF) carrier identification.

STUDY DESIGN

New technologies allow the measurement of the second IRT level solely in infants with an elevated first IRT level. Specimens with an elevated second IRT level undergo mutation analysis. We tested the projected efficacy with retrospective data from Colorado.

RESULTS

All known infants with CF would have been identified with our proposed IRT cutoff points, and 3 would have been missed with our mutation panel. Two of 3 missed cases would have been identified by using a failsafe method (IRT >99.9th percentile), yielding a sensitivity rate of 99.7% (95% CI, 98.4-99.9). Estimated reduction in carrier detection was 80% compared with IRT/DNA.

CONCLUSION

IRT/IRT1 upward arrow/DNA appears to improve cystic fibrosis newborn screen sensitivity while decreasing carrier identification, providing an alternative to IRT/IRT in states that obtain 2 blood spots.

Clarification of laboratory and clinical variables that influence cystic fibrosis newborn screening with initial analysis of immunoreactive trypsinogen

OBJECTIVES

To ensure that each newborn receives an equitable test of the highest possible sensitivity, we recognized the necessity to reassess immunoreactive trypsinogen and DNA issues in cystic fibrosis newborn screening algorithms. Our objectives included clarification of various factors that influence immunoreactive trypsinogen concentrations and resolution of long-standing questions about variations in immunoreactive trypsinogen levels among newborns.

METHODS

Immunoreactive trypsinogen data on 660443 newborns who were born between July 1, 1994, and June 30, 2004, were abstracted from the Wisconsin State Laboratory of Hygiene databases and deidentified for analysis. Using a compiled data set, we analyzed various demographic characteristics to determine their role, if any, in immunoreactive trypsinogen variation. Specifically, season of birth, reagent lot, and birth weight were examined. Sensitivities of the most common cystic fibrosis newborn screening protocols, namely immunoreactive trypsinogen/immunoreactive trypsinogen and immunoreactive trypsinogen/DNA, were also investigated.

RESULTS

Mean and 95th percentile immunoreactive trypsinogen levels were shown to vary by both season and reagent lot number and affect sensitivity of the assay. Low birth weight infants had significantly higher immunoreactive trypsinogen values than normal birth weight infants. Sensitivities were also found to vary on the basis of the algorithm used, with the highest sensitivity of 96.2% calculated for an immunoreactive trypsinogen/DNA protocol with 23 cystic fibrosis transmembrane conductance regulator mutation analyses compared with 80.2% with the immunoreactive trypsinogen/immunoreactive trypsinogen method used in 9 states.

CONCLUSIONS

Floating, rather than fixed, cutoff values for the initial immunoreactive trypsinogen portion of any cystic fibrosis newborn screening protocol are generally necessary on the basis of the seasonal and reagent lot variations observed. Because of its lower sensitivity, immunoreactive trypsinogen/immunoreactive trypsinogen does not optimize detection of patients with cystic fibrosis.

Targeted extended cystic fibrosis mutation testing on known and at-risk patients and relatives

This paper reports mathematically derived residual risks of being a carrier or being affected with cystic fibrosis following various screening scenarios to assist in interpreting test results and advising patients. While parental screening with 23 American College of Medical Genetics (ACMG) cystic fibrosis mutations defines the 64% of affected U.S. Caucasian fetuses with two detectable mutations, newborn screening for elevated immunoreactive trypsinogen (IRT) and sweat chloride identifies an additional 36% of affected newborns with zero or one detected mutation. The relatives of these affected newborns with less than two detectable mutations have higher posterior (after) 23 mutation-negative test risks of carrying undetected mutations. These calculations emphasize how knowledge of the mutations in the related affected patient substantially improves upon the quality of after-test advice to patients. Furthermore, negative tests of the partner without a family history and/or more extensive cystic fibrosis transmembrane conductance regulator (CFTR) gene testing also increases the likelihood that a negative report is truly negative. When a newborn patient with zero or one detected CFTR mutation has an inconclusive sweat test result, the sweat test should be repeated before ordering additional often unnecessary CFTR gene sequencing. Given the same composite mutation panel test accuracy, a higher proportion of reported test results would be correct during parental screening than when testing at-risk fetuses or symptomatic newborns. Prenatal and newborn screening would be enhanced substantially by medical professionals offering copies of all positive parental and newborn test reports to the parents to share with their relatives. These principles are likely to be applicable to other genetic diseases as the most common mutation frequencies are reported.

Triose phosphate isomerase deficiency is caused by altered dimerization--not catalytic inactivity--of the mutant enzymes

Triosephosphate isomerase (TPI) deficiency is an autosomal recessive disorder caused by various mutations in the gene encoding the key glycolytic enzyme TPI. A drastic decrease in TPI activity and an increased level of its substrate, dihydroxyacetone phosphate, have been measured in unpurified cell extracts of affected individuals. These observations allowed concluding that the different mutations in the TPI alleles result in catalytically inactive enzymes. However, despite a high occurrence of TPI null alleles within several human populations, the frequency of this disorder is exceptionally rare. In order to address this apparent discrepancy, we generated a yeast model allowing us to perform comparative in vivo analyses of the enzymatic and functional properties of the different enzyme variants. We discovered that the majority of these variants exhibit no reduced catalytic activity per se. Instead, we observed, the dimerization behavior of TPI is influenced by the particular mutations investigated, and by the use of a potential alternative translation initiation site in the TPI gene. Additionally, we demonstrated that the overexpression of the most frequent TPI variant, Glu104Asp, which displays altered dimerization features, results in diminished endogenous TPI levels in mammalian cells. Thus, our results reveal that enzyme deregulation attributable to aberrant dimerization of TPI, rather than direct catalytic inactivation of the enzyme, underlies the pathogenesis of TPI deficiency. Finally, we discovered that yeast cells expressing a TPI variant exhibiting reduced catalytic activity are more resistant against oxidative stress caused by the thiol-oxidizing reagent diamide. This observed advantage might serve to explain the high allelic frequency of TPI null alleles detected among human populations.

Genetic and physiologic correlates of longitudinal immunoreactive trypsinogen decline in infants with cystic fibrosis identified through newborn screening

OBJECTIVES

To characterize the time course and physiologic significance of decline in serum immunoreactive trypsinogen (IRT) levels in infants with cystic fibrosis (CF) by mode of diagnosis and genotype, and to examine IRT heritability.

STUDY DESIGN

We studied longitudinal IRT measurements in 317 children with CF. We developed statistical models to describe IRT decline. Pancreatic disease severity (Mild or Severe) was assigned using CF genotype and was confirmed in 47 infants through fat malabsorption studies.

RESULTS

Infants with severe disease exhibited IRT decline with non-detectable levels typically seen by 5 years of age. Infants with mild disease exhibited a decline in the first 2 years, asymptomatically approaching a level greater than published norms. IRT and fecal fat were inversely correlated. IRT values in infants with meconium ileus (MI) were significantly lower than newborn-screened infants at birth. The high proportion of shared variation in predicted IRT values among sibling pairs with severe disease suggests that IRT is heritable.

CONCLUSIONS

IRT declines characteristically in infants with CF. Lower IRT values in newborns with MI suggest increased pancreatic injury. Furthermore, IRT is heritable among patients with severe disease suggesting genetic modifiers of early CF pancreatic injury. This study demonstrates heritability of a statistically modeled quantitative phenotype.

Cost-effectiveness of 4 neonatal screening strategies for cystic fibrosis

OBJECTIVES

The purpose of this work was to assess the costs of 4 neonatal screening strategies for cystic fibrosis in relation to health effects. In each strategy, the first test was the measurement of serum concentration of immunoreactive trypsin. The second step consisted of either a second immunoreactive trypsin test (strategy 1) or a multiple mutation analysis (strategy 2). In strategies 3 and 4, a third step was added to strategy 2: a second immunoreactive trypsin test (strategy 3) or an extended mutation analysis of the cystic fibrosis gene, that is, a denaturing gradient gel electrophoresis analysis (strategy 4).

METHODS

We conducted an economic-modeling exercise in the Netherlands based on published data and expert opinions. Subjects were a hypothetical cohort of 200 000 neonates, the approximate number of children born annually in the Netherlands, and we assessed the costs and number of life-years gained as a result of neonatal screening for cystic fibrosis. The costs and effects of changes in reproductive decisions because of neonatal screening were also assessed.

RESULTS

Immunoreactive trypsin + immunoreactive trypsin had the most favorable cost-effectiveness ratio of 24,800 euro per life-year gained. Immunoreactive trypsin + DNA + denaturing gradient gel electrophoresis achieved more health effects than immunoreactive trypsin + DNA + immunoreactive trypsin at lower cost. The incremental costs per life-year gained of the immunoreactive trypsin + DNA + denaturing gradient gel electrophoresis strategy compared with the immunoreactive trypsin + immunoreactive trypsin strategy were 130,700 euro, whereas the incremental costs of the immunoreactive trypsin + DNA strategy compared with the immunoreactive trypsin + DNA + denaturing gradient gel electrophoresis strategy were 2,154,300 euro. When changes in reproductive decisions as a result of neonatal screening are also taken into account, neonatal screening for cystic fibrosis may lead to financial savings of approximately 1.8 million euro annually, depending on the screening strategy used.

CONCLUSIONS

Cystic fibrosis screening for neonates is a good economic option, and positive health effects can also be expected. Immunoreactive trypsin + immunoreactive trypsin and immunoreactive trypsin + DNA + denaturing gradient gel electrophoresis are the most cost-effective strategies.

Pediatricians' attitudes toward expanding newborn screening

OBJECTIVE

Traditional population screening focuses on conditions for which early treatment prevents severe morbidity and mortality. The classic example in pediatrics is newborn screening for phenylketonuria, which began in the 1960s. In 1968, Wilson and Jungner delineated 10 criteria that would justify population screening. These criteria have been reaffirmed by many newborn screening task forces as the standard for adding conditions to newborn screening programs. Today, however, some newborn screening programs are expanding to include conditions that may not meet all of the traditional screening criteria. Little is known about pediatricians' attitudes toward expanding screening. We examine the attitudes of pediatricians and pediatric subspecialists toward screening for cystic fibrosis (CF), Duchenne muscular dystrophy (DMD), fragile X, and type 1 diabetes.

METHODS

A cross-sectional survey was conducted of 600 pediatricians, including those who are members of the section of genetics, endocrinology, pulmonology, and neurology of the American Academy of Pediatrics. For each condition, pediatricians were queried about (1) testing high-risk infants, (2) newborn screening, and (3) population screening or testing beyond the newborn period. Demographic data were also collected.

RESULTS

A total of 232 (43%) of 537 eligible pediatricians returned surveys. More than 75% support testing high-risk infants for all conditions except type 1 diabetes. CF was the only condition for which >50% supported newborn screening. Newborn screening was preferred over screening older infants for all conditions except fragile X. Subspecialty affiliation did not have a significant impact with respect to attitudes about testing high-risk children, newborn screening, or screening beyond infancy. We analyzed the data by the number of patients with the queried condition under the physician's care and by the number of affected family members. Neither aspect was significant. We also analyzed the data by gender, by year of residency graduation, and by geographic location. None of these factors revealed significant differences in responses. For each condition, 8% to 41% of physicians would personally choose to test their own infant. We found that physicians' opinion about what they would want for their own children correlated with their attitude about population newborn screening. Those who would personally choose testing of their own infants were highly likely to support newborn screening for CF (98%), DMD (94%), and fragile X (98%), but only 78% of those who would personally opt for newborn screening of type 1 diabetes would also endorse population-based screening. This was statistically significant for each condition. Those who would choose not to test their own infants were significantly less likely to support newborn screening of the general population. One third of those who did not want to test their own newborns for CF supported population screening, whereas only one fifth supported DMD and fragile X population screening. For type 1 diabetes, 98% of those who would not personally choose newborn testing did not want it offered as a population screening program.

CONCLUSIONS

Most physicians support diagnostic genetic testing of high-risk children but are less supportive of expanding newborn screening, particularly for conditions that do not meet the Wilson and Jungner criteria. Willingness to expand newborn screening does not correlate with professional characteristics but rather with personal interest in testing of their own children.

Two-tiered immunoreactive trypsinogen-based newborn screening for cystic fibrosis in Colorado: screening efficacy and diagnostic outcomes

OBJECTIVE

To examine immunoreactive trypsinogen (IRT)-based screening for cystic fibrosis (CF) for recall rate, genotype distribution, and "borderline" sweat test results.

STUDY DESIGN

CF newborn screening in Colorado began in 1982, and >1,153,000 infants were screened through 2002 with an IRT-based screen (IRT/IRT).

RESULTS

We have identified 313 infants with CF, giving an overall incidence of 1 in 3684 and a Hispanic incidence of 1 in 6495. Fifty-five infants with meconium ileus (17.6%) were excluded from analysis. Fourteen infants with false-negative results were identified (5.4%). The average recall rate was 0.6%, with a positive predictive value of 4.7%. Ninety-three percent of the infants had at least 1 DeltaF508 mutation, and 98% of the infants had at least 1 mutation from the American College of Medical Genetics recommended panel. Six infants had hypertrypsinogenemia and borderline results on sweat tests (30-60 mmol/L). Increased variability in sweat chloride levels were seen in these infants compared with infants with homozygous DeltaF508. Three children with initial borderline results on sweat tests had CF diagnosed.

CONCLUSIONS

The recall and false-negative rates of our IRT/IRT CF screening program are reported. Additionally, genotypes of the patients identified mirror the CF population genotypes, reflecting similar disease severity in the screened population. Finally, infants with persistent hypertrypsinogenemia and borderline sweat test results need long-term follow-up.

Diagnostic dilemmas resulting from the immunoreactive trypsinogen/DNA cystic fibrosis newborn screening algorithm

OBJECTIVE

To quantitate the proportion of infants identified through cystic fibrosis (CF) newborn screening (NBS) by an immunoreactive trypsinogen (IRT)/DNA screening algorithm who have an unclear diagnosis as defined by the findings of an elevated IRT level and either 1) 2 CF gene (CFTR) mutations detected and sweat chloride level <60 mEq/L; or 2) 0 or 1 CFTR mutations and a "borderline" sweat chloride level >or=30 and <60 mEq/L.

STUDY DESIGN

Using the 4-year cohort of CF-affected infants recently described by the Massachusetts CF NBS program, we identified and described the number of infants with the diagnostic characteristics (diagnostic dilemmas) aforementioned.

RESULTS

Of infants with positive results on CF NBS who had 1 CFTR mutation detected and a borderline sweat chloride concentration, nearly 20% displayed a second CFTR mutation on further evaluation. Of all infants with positive CF NBS results considered affected with CF, 11% had a diagnosis that fell into 1 of the diagnostic dilemma categories aforementioned.

CONCLUSIONS

Four problematic diagnostic categories generated by CF NBS are defined. In the absence of data on the natural history of such infants, careful follow-up is recommended for infants in whom a definitive diagnosis is elusive.

Challenges in implementing a successful newborn cystic fibrosis screening program

OBJECTIVE

To identify necessary components of a successful cystic fibrosis (CF) newborn screening (NBS) program.

STUDY DESIGN

The approach to CF NBS used by the Massachusetts NBS program was examined.

RESULTS

Several key components were identified that should be addressed when a state has made the decision to screen, and well in advance of actual implementation. These components include (1) inclusion of CF center directors in the development process; (2) logistics of choosing a screening algorithm relative to practices in place and community wishes; (3) projections of medical service needs from specific algorithms; (4) identification of critical reporting components; (5) identification of critical follow-up components; and (6) recognition of educational needs.

CONCLUSIONS

Careful examination of a wide variety of issues is needed to ensure optimal implementation of NBS for CF.

Sweat-testing in preterm and full-term infants less than 6 weeks of age

Our objective was to examine the characteristics of preterm and full-term infants < or = 6 weeks old that influence the success of obtaining sufficient sweat for diagnosis of CF, and corresponding sweat chloride concentrations. A retrospective chart review of 119 sweat tests was performed on 103 preterm and full-term infants < or = 6 weeks of age. Bivariate and multivariate regression analyses were used to determine the predictors of successful sweat testing and characteristics influencing sweat chloride concentrations. Adequate amounts of sweat (> or = 75 mg) were obtained for analysis in 73.8% of initial attempts in the infant group. The following characteristics were associated with increased odds of obtaining a quantity not sufficient (QNS) for sweat chloride concentration measurement: African-American race, infant weight < 2,000 g, preterm birth, and postmenstrual age (PMA) < 36 weeks. With a multivariable logistic model, the only significant predictors were African-American race (7.3, 2.4-21.7) and PMA < 36 weeks (17.9, 4.2-75.9). Sweat chloride concentration in non-CF individuals is inversely related to both gestational age and age at testing, and this effect is additive in a linear regression model. In conclusion, sweat collection can be reliably performed in infants > or = 36 weeks postmenstrual age, > 2,000 g, and > 3 days postnatal age. Maturational factors have a mild impact on sweat chloride concentration.