Newborn screening for cystic fibrosis: techniques and strategies

The first five-year evaluation of cystic fibrosis neonatal screening program in São Paulo State, Brazil

The Hospital of the Ribeirão Preto Medical School, University of São Paulo is one of the three screening centers in São Paulo State, Brazil, and has included a test for cystic fibrosis (CF) since February 6, 2010, by a court order. We evaluated the first five years of this CF-newborn screening program. The original immunoreactive trypsinogen (IRT)/IRT screening protocol was adopted in Brazil. A total of 173,571 newborns were screened, 1,922 (1.1%) of whom showed IRT1 ≥ 70ng/mL. Of these, 1,795 (93.4%) collected IRT2, with elevated results (IRT2 ≥ 70ng/mL) in 102 of them (5.2%). We identified a total of 26 CF cases during this period, including three CF cases that were not detected by the CF-newborn screening. The incidence of the disease among the screened babies was 1:6,675 newborns screened. Median age at the initial evaluation was 42 days, comparable to that of neonates screened with the IRT/DNA protocol. Almost all infants with CF already exhibited some manifestations of the disease during the neonatal period. The mutation most frequently detected in the CF cases was F508del. These findings suggest the early age at the beginning of treatment at our center was due to the effort of the persons involved in the program regarding an effective active search. Considering the false negative results of CF-newborn screening and the early onset of clinical manifestations of the disease in this study, pediatricians should be aware of the diagnosis of CF even in children with negative test.

Translating Molecular Technologies into Routine Newborn Screening Practice

As biotechnologies advance and better treatment regimens emerge, there is a trend toward applying more advanced technologies and adding more conditions to the newborn screening (NBS) panel. In the current Recommended Uniform Screening Panel (RUSP), all conditions but one, congenital hypothyroidism, have well-defined genes and inheritance patterns, so it is beneficial to incorporate molecular testing in NBS when it is necessary and appropriate. Indeed, the applications of molecular technologies have taken NBS to previously uncharted territory. In this paper, based on our own program experience and what has been reported in the literature, we describe current practices regarding the applications of molecular technologies in routine NBS practice in the era of genomic and precision medicine.

Initial regional evaluation of the Cystic Fibrosis Newborn Screening Program: data from the Mediterranean coast of Turkey

Background/ aim

Since January 2015, the Cystic Fibrosis Newborn Screening (CFNS) program has been implemented in Turkey. We aimed to evaluate the demographic, clinical, and laboratory data of cases referred from the CFNS program and to determine the most suitable cut-off value for immunoreactive trypsinogen (IRT)-1 and immunoreactive trypsinogen (IRT-2) that are used in the CFNS program in Turkey.

Materials and methods

A total of 156 Turkish Caucasian subjects were determined as positive cases during 3 years, from January 2015 to January 2018, and were referred to the pediatric pulmonology clinics of Akdeniz University Hospital, Antalya, Turkey, for the national CFNS program. The evaluation was made considering the IRT-1 and IRT-2 values, demographic characteristics, sweat test results, CFTR genotypes, and diagnoses.

Results

Nine patients were diagnosed with cystic fibrosis (CF). Eight were diagnosed with CF-related metabolic syndromes and three were determined to be CF carriers. The ratio of CF to CF-related metabolic syndrome was determined as 1.1:1. Considering the limits of the present CFNS program and the IRT method, the positive predictive value (PPV) for the referred cases was determined as 5.8%. When a cut-off value of 105.6 ng/mL was taken for IRT-1, sensitivity was 100%, specificity was 59%, and PPV was 12.8%. For a cut-off value of 88.75 ng/mL for IRT-2, sensitivity was determined as 90%, specificity as 65%, and PPV as 15.2%.

Conclusion

This is the first detailed clinical study to evaluate the data from the CFNS program along the Mediterranean coast of Turkey. As false positive results are extremely high in Turkey, there is an urgent need for revision of the IRT-1 and IRT-2 limits by evaluating the data of the whole country.

Initial Evaluation of Prospective and Parallel Assessments of Cystic Fibrosis Newborn Screening Protocols in Eastern Andalusia: IRT/IRT versus IRT/PAP/IRT

Identifying newborns at risk for cystic fibrosis (CF) by newborn screening (NBS) using dried blood spot (DBS) specimens provides an opportunity for presymptomatic detection. All NBS strategies for CF begin with measuring immunoreactive trypsinogen (IRT). Pancreatitis-associated protein (PAP) has been suggested as second-tier testing. The main objective of this study was to evaluate the analytical performance of an IRT/PAP/IRT strategy versus the current IRT/IRT strategy over a two-year pilot study including 68,502 newborns. The design of the study, carried out in a prospective and parallel manner, allowed us to compare four different CF-NBS protocols after performing a post hoc analysis. The best PAP cutoff point and the potential sources of PAP false positive results in our non-CF newborn population were also studied. 14 CF newborns were detected, resulting in an overall CF prevalence of 1/4, 893 newborns. The IRT/IRT algorithm detected all CF cases, but the IRT/PAP/IRT algorithm failed to detect one case of CF. The IRT/PAP/IRT with an IRT-dependent safety net protocol was a good alternative to improve sensitivity to 100%. The IRT × PAP/IRT strategy clearly performed better, with a sensitivity of 100% and a positive predictive value (PPV) of 39%. Our calculated optimal cutoffs were 2.31 µg/L for PAP and 167.4 µg2/L2 for IRT × PAP. PAP levels were higher in females and newborns with low birth weight. PAP false positive results were found mainly in newborns with conditions such as prematurity, sepsis, and hypoxic-ischemic encephalopathy.

Metabolite accumulation in VLCAD deficiency markedly disrupts mitochondrial bioenergetics and Ca2+ homeostasis in the heart

We studied the effects of the major long-chain fatty acids accumulating in very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency, namely cis-5-tetradecenoic acid (Cis-5) and myristic acid (Myr), on important mitochondrial functions in isolated mitochondria from cardiac fibers and cardiomyocytes of juvenile rats. Cis-5 and Myr at pathological concentrations markedly reduced mitochondrial membrane potential (ΔΨ_m ), matrix NAD(P)H pool, Ca²⁺ retention capacity, ADP- (state 3) and carbonyl cyanide 3-chlorophenyl hydrazine-stimulated (uncoupled) respiration, and ATP generation. By contrast, these fatty acids increased resting (state 4) respiration (uncoupling effect) with the involvement of the adenine nucleotide translocator because carboxyatractyloside significantly attenuated the increased state 4 respiration provoked by Cis-5 and Myr. Furthermore, the classical inhibitors of mitochondrial permeability transition (MPT) pore cyclosporin A plus ADP, as well as the Ca²⁺ uptake blocker ruthenium red, fully prevented the Cis-5- and Myr-induced decrease in ΔΨ_m in Ca²⁺ -loaded mitochondria, suggesting, respectively, the induction of MPT pore opening and the contribution of Ca²⁺ toward these effects. The findings of the present study indicate that the major long-chain fatty acids that accumulate in VLCAD deficiency disrupt mitochondrial bioenergetics and Ca²⁺ homeostasis, acting as uncouplers and metabolic inhibitors of oxidative phosphorylation, as well as inducers of MPT pore opening, in the heart at pathological relevant concentrations. It is therefore presumed that a disturbance of bioenergetics and Ca²⁺ homeostasis may contribute to the cardiac manifestations observed in VLCAD deficiency.

Very long-chain acyl-CoA dehydrogenase (VLCAD-) deficiency-studies on treatment effects and long-term outcomes in mouse models

Very-long-chain-acyl-CoA-dehydrogenase deficiency is the most common disorder of mitochondrial long-chain fatty acid (LCFA) oxidation, with an incidence of 1:50,000-1:100,000 in newborns. Catabolic situations contribute to the aggravation of symptoms and induce severe metabolic derangement. Treatment for VLCAD-deficiency includes avoidance of fasting and a long-chain fat-restricted and fat-modified diet in which LCFAs are fully or partially replaced by medium-chain triglycerides (MCT). The aim of this work was to investigate the outcome and the effects of long-term treatment in a mouse model of VLCAD-deficiency. The application of a single MCT bolus in a mouse model of VLCAD-deficiency (VLCAD^-/- mice) immediately prior to exercise protected the muscles from the accumulation of acylcarnitines providing the required energy and it did not affect hepatic lipid metabolism. However, when MCT was applied over the course of a year as a regular part of the diet, female VLCAD^-/- mice developed a severe clinical phenotype comparable to the human metabolic syndrome. Indeed, they were characterized by massive visceral fat infiltration, hepatosteatosis, disturbed fatty acid composition, hyperlipidemia, and systemic oxidative stress. In contrast, male VLCAD^-/- mice seemed to be protected and displayed only signs of insulin resistance. Besides the sex-specific response to MCT supplementation with regard to the lipid metabolism, all VLCAD^-/- mice developed progressive cardiac dysfunction over time which worsened when they were treated with regular MCT resulting in severe dilated cardiomyopathy. While long term use of MCT oil in mice has adverse effects, no such effects have been demonstrated in humans, likely reflecting the differences in long chain fatty acid oxidation between the two species.

To know or not to know, disclosure of a newborn carrier screening test result for cystic fibrosis

PURPOSE

Most newborn screening (NBS) strategies for Cystic Fibrosis (CF) also identify carriers. However, it is unclear if parents want to be informed about their child's carrier status or not.

METHODS

Focus group discussions with pregnant couples to explore their opinions about disclosure of a carrier result for CF of their newborn.

RESULTS

All (n = 30) wanted to be informed when newborn screening would show their newborn being a CF-carrier. Their main reason was the implication of this knowledge for further family planning. Other family members could be informed and children within the family could be tested. Parents stated they have the right to know, but others also expressed that the choice of not being informed should be offered as well.

CONCLUSION

Most parents want to be informed when NBS for CF reveals that their child is a CF-carrier, but the choice of not being informed should also be offered.

The influence of sex, gestational age, birth weight, blood transfusion, and timing of the heel prick on the pancreatitis-associated protein concentration in newborn screening for cystic fibrosis

BACKGROUND

Pancreatitis-associated protein (PAP) is currently discussed as a marker in newborn screening (NBS) for cystic fibrosis (CF). However, it is not known if PAP concentrations are influenced by sex, gestational age, birth weight, blood transfusion or time of collection and what this would mean for NBS for CF.

METHODS

In 2008 all newborns in part of the Netherlands were screened for CF by an IRT/PAP protocol. PAP concentration was determined by the MucoPAP ELISA (DynaBio), which was modified to a Dissociation Enhanced Lanthanide Fluoroimmunoassay (DELFIA) method following a protocol of PerkinElmer.

RESULTS

In healthy newborns, the median PAP concentration was 0.5 μg/l (Interquartile range (IQR 0.3-0.8) whereas this was 3.2 μg/l (IQR 2.0-12.5) in CF infants. PAP concentrations were lower in premature infants 0.94 and 0.91 times for 25 to 31 + 6 weeks GA and 32 to 36 + 6 weeks respectively. A higher PAP concentration was observed in low-birth-weight infants (<2500 gram)(p = 0.001), per 100 gram birth weight gained the PAP concentration decreased with 0.1 %. PAP levels were higher after a blood transfusion, the 95th percentile increased from 1.3 to 3.6 μg/l leading to a higher false-positive rate. The PAP concentration increased when newborn screening was performed more than 168 hours (day 7) after birth (β = 1.63), the 95th percentile increased from 1.3-1.6 μg/l to 4.0 μg/l after 168 hours (72,874 newborns were screened).

CONCLUSION

Sex, birth weight, and gestational age lead to small differences in PAP concentrations without consequences for the screening algorithm. However, blood transfusion as well as performance of the heel prick after 168 hours (7 days) lead to clinically significant higher PAP levels and to a higher risk on a false-positive screening test result.

Dried blood spots for the enzymatic diagnosis of lysosomal storage diseases in dogs and cats

BACKGROUND

In people, lysosomal storage diseases (LSD) can be diagnosed by assaying enzyme activities in dried blood spots (DBS).

OBJECTIVE

The aim of this study was to evaluate the feasibility of using DBS samples from dogs and cats to measure lysosomal enzymatic activities and diagnose LSD.

METHODS

Drops of fresh whole blood collected in EDTA from dogs and cats with known or suspected LSD and from clinically healthy dogs and cats were placed on neonatal screening cards, dried, and mailed to the Metabolic Laboratory, University Children's Hospital, Frankfurt, Germany. Activities of selected lysosomal enzymes were measured using fluorescent substrates in a 2-mm diameter disk (~2.6 μL blood) punched from the DBS. Results were expressed as nmol substrate hydrolyzed per mL of blood per minute or hour.

RESULTS

Reference values were established for several lysosomal enzyme activities in DBS from dogs and cats; for most enzymes, activities were higher than those published for human samples. Activities of β-glucuronidase, N-acetylglucosamine-4-sulfatase (arylsulfatase B), α-mannosidase, α-galactosidase, α-fucosidase, and hexosaminidase A were measureable in DBS from healthy cats and dogs; α-iduronidase activity was measureable only in cats. In samples from animals with LSD, markedly reduced activity of a specific enzyme was found. In contrast, in samples from cats affected with mucolipidosis II, activities of lysosomal enzymes were markedly increased.

CONCLUSIONS

Measurement of lysosomal enzyme activities in DBS provides an inexpensive, simple, and convenient method to screen animals for suspected LSD and requires only a small sample volume. For diseases in which the relevant enzyme activity can be measured in DBS, a specific diagnosis can be made.

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.

New technologies extend the scope of newborn blood-spot screening, but old problems remain unresolved

The potential of newborn blood-spot screening is expanding rapidly with the development of new analytical techniques and treatment methods. At the same time, some existing programmes, particularly that for congenital hypothyroidism, are coming under scrutiny because of suspicion that they are being shaped by analytical performance rather than evidence of clinical need. Screening policy varies greatly from country to country.

CONCLUSION

  Ethical and political considerations may sometimes override formal scientific decision models.

Frequency of Usher syndrome in two pediatric populations: Implications for genetic screening of deaf and hard of hearing children

PURPOSE

Usher syndrome is a major cause of genetic deafness and blindness. The hearing loss is usually congenital and the retinitis pigmentosa is progressive and first noticed in early childhood to the middle teenage years. Its frequency may be underestimated. Newly developed molecular technologies can detect the underlying gene mutation of this disorder early in life providing estimation of its prevalence in at risk pediatric populations and laying a foundation for its incorporation as an adjunct to newborn hearing screening programs.

METHODS

A total of 133 children from two deaf and hard of hearing pediatric populations were genotyped first for GJB2/6 and, if negative, then for Usher syndrome. Children were scored as positive if the test revealed > or =1 pathogenic mutations in any Usher gene.

RESULTS

Fifteen children carried pathogenic mutations in one of the Usher genes; the number of deaf and hard of hearing children carrying Usher syndrome mutations was 15/133 (11.3%). The population prevalence was estimated to be 1/6000.

CONCLUSION

Usher syndrome is more prevalent than has been reported before the genome project era. Early diagnosis of Usher syndrome has important positive implications for childhood safety, educational planning, genetic counseling, and treatment. The results demonstrate that DNA testing for Usher syndrome is feasible and may be a useful addition to newborn hearing screening programs.

Nutritional considerations in patients with cystic fibrosis

Nutritional status is strongly associated with pulmonary function and survival in cystic fibrosis patients. Attainment of a normal growth pattern in childhood and maintenance of adequate nutritional status in adulthood represent major goals of multidisciplinary cystic fibrosis centers. International guidelines on energy intake requirements, pancreatic enzyme-replacement therapy and fat-soluble vitamin supplementation are of utmost importance in daily practice. The present review summarizes the most up-to-date information on early nutritional management in newly diagnosed patients and evaluates the benefits of aggressive nutritional support, assessment of nutritional status, recommendations for nutrition-related management in pancreatic-insufficient patients and the possible therapeutic impact of fat intake modulation upon inflammatory status.

Newborn screening for cystic fibrosis by use of a multiplex immunoassay

BACKGROUND

Since its beginnings, newborn screening for cystic fibrosis (CF) using an assay for immunoreactive trypsinogen (IRT) has been plagued by a high rate of false-positive results (screen positive, diagnosis negative), despite attempts to reduce this rate by use of altered cutoffs and second-tier DNA testing. IRT exists as 2 isoforms: IRT1 and IRT2, with IRT2 being more closely aligned with pancreatic disease, including CF. Assay standardization between programs is a continuing problem because the IRT assays currently in use variously recognize either 1 or both isoforms. Here we report the development of a multiplexed assay for both forms of IRT simultaneously.

METHODS

Using 2 different Luminex bead sets, we developed assays for each IRT isoform separately and then combined them. Using the sum of IRT1 and IRT2 values (IRT1+IRT2), we compared the results with a CF kit currently in use.

RESULTS

In a sample set consisting of 16 cases confirmed positive for CF, we established a cutoff at >97 microg/L total IRT. Seven of 8 carriers with 1 CF mutation screen-positive by the standard method were also screen-positive by IRT1+IRT2. Of 32 cases screen-positive by standard IRT, 11 were screen-negative by IRT1+IRT2. None of these 11 cases had CF mutations identified by the screening program.

CONCLUSIONS

These data indicate that the multiplex method with specificity for 2 isoforms of IRT has performance comparable to that of a standard IRT method and the advantage of improved standardization by detection of the 2 isoforms.

Inconclusive cystic fibrosis neonatal screening results: long-term psychosocial effects on parents

AIM

Cystic Fibrosis (CF) Newborn Screening occasionally identifies neonates where a CF diagnosis can neither be confirmed nor excluded. To assess how parents of these infants cope with this ambiguous situation.

METHODS

Parents of 11 children with Ambiguous Diagnosis (group AD) were compared with parents of 11 children diagnosed with CF through neonatal screening [group Cystic Fibrosis Diagnosis (CFD)] and with parents of 11 Healthy Control children (group HC) matched for gender and age.

RESULTS

The emotional reaction to the inconclusive result was less pronounced in AD than in CFD (p = 0.003), and AD parents considered their infants as healthy as controls. Parents' anxiety about their child's health is stronger in CFD than in AD (p < 0.05) and HC (p < 0.001). Long-term emotional distress was rated similarly in AD and CFD, and greater than in HC (p = 0.0003). The parent/child relationship was less influenced in AD than in the CF group (p = 0.03). Seven AD and CFD parents changed their family planning projects.

CONCLUSION

Inconclusive neonatal screening results appear to be understood and associated with lower anxiety levels than CF diagnosis. Concern about the child's health is similar to healthy controls and lower than in parents of CF children.

Newborn blood spot screening: new opportunities, old problems

Newborn screening is evolving very rapidly. Geographical coverage is expanding, particularly for common disorders such as congenital hypothyroidism. New technologies, particularly tandem mass spectrometry and high throughput mutation analysis, have increased greatly the range of disorders which could be covered. However, these new possibilities are being exploiting at very different rates in different countries. This is due in part to the different ways in which generally-accepted screening criteria, based on the ten principles of Wilson and Jungner, are being interpreted and applied to policy. The appropriate management of some of the conditions newly-detectable by screening also remains controversial and there is a pressing need to align screening policy and clinical practice. Critical analysis and careful collection of data on an international basis are required to resolve these issues.

Newborn screening for cystic fibrosis offers an advantage over symptomatic diagnosis for the long term benefit of patients: the motion for

Comprehensive newborn screening for cystic fibrosis has occurred for more than 25 years in some regions and the results of randomised controlled trials reporting the outcomes have been published. Testing protocols for CF have recently been reviewed and the sensitivity and specificity of these protocols are high. In spite of this, many remain sceptical in respect of the advantages conferred by newborn screening for CF. Every study of newborn screening has shown that diagnosis occurs at a significantly younger age. While this alone is sufficient to justify newborn screening, the clinical course of those diagnosed via newborn screening indicates that many additional advantages accrue. These include a decreased morbidity and mortality in early life, facilitation of better growth and prevention of vitamin deficiency in early infancy, as well as some indication of an advantage in terms of pulmonary status later in life. This review summarises the arguments in favour of newborn screening for CF.

Implementation of genetics to personalize medicine

BACKGROUND

We stand on the verge of integrating individual genetic and genomic information into health care provision and maintenance to improve health, increase efficiency, and decrease costs. We are beginning to integrate information on inherited susceptibility, gene expression, and predicted pharmacogenomic response to refine our medical management.

OBJECTIVE

This article reviews the current utility of genetics and genomics in a wide array of clinical circumstances, considers the future applications, and defines some of the obstacles and potential solutions to clinical integration of genomic medicine.

METHODS

Using the search terms genetics, genomics, pharmacogenomics, newborn screening, long QT syndrome, BRCA1/BRCA2, maturity onset diabetes of youth, diabetes, hemochromatosis, coronary artery disease, copy number changes, genetic discrimination, and genetic education, the PubMed database was searched from January 2000 to March 2007 to identify pertinent articles. Search results were restricted to English-language and human studies.

RESULTS

Several areas of medicine have begun to incorporate genetics into clinical practice, including newborn screening and breast cancer risk stratification and treatment. Molecular genetic tests are, and will increasingly become, available for inherited arrhythmias, diabetes, cancer, coronary artery disease, and pharmacogenomics. However, there are many barriers to implementation, including the cost of testing, the genetic literacy of patients and health care providers, and concerns about genetic discrimination.

CONCLUSION

Genetics and genomics will be increasingly utilized in every field of medicine; however, health care providers and patients must have realistic expectations about its predictive power and current limitations.