Newborn screening for cystic fibrosis in Wisconsin: comparison of biochemical and molecular methods

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.

Missed Cystic Fibrosis Newborn Screening Cases due to Immunoreactive Trypsinogen Levels below Program Cutoffs: A National Survey of Risk Factors

Testing immunoreactive trypsinogen (IRT) is the first step in cystic fibrosis (CF) newborn screening. While high IRT is associated with CF, some cases are missed. This survey aimed to find factors associated with missed CF cases due to IRT levels below program cutoffs. Twenty-nine states responded to a U.S-wide survey and 13 supplied program-related data for low IRT false screen negative cases (CFFN) and CF true screen positive cases (CFTP) for analysis. Rates of missed CF cases and odds ratios were derived for each factor in CFFNs, and two CFFN subgroups, IRT above ("high") and below ("low") the CFFN median (39 ng/mL) compared to CFTPs for this entire sample set. Factors associated with "high" CFFN subgroup were Black race, higher IRT cutoff, fixed IRT cutoff, genotypes without two known CF-causing variants, and meconium ileus. Factors associated with "low" CFFN subgroup were older age at specimen collection, Saturday birth, hotter season of newborn dried blood spot collection, maximum ≥ 3 days laboratories could be closed, preterm birth, and formula feeding newborns. Lowering IRT cutoffs may reduce "high" IRT CFFNs. Addressing hospital and laboratory factors (like training staff in collection of blood spots, using insulated containers during transport and reducing consecutive days screening laboratories are closed) may reduce "low" IRT CFFNs.

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.

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.

Factors associated with moderate neonatal hyperthyrotropinemia

BACKGROUND

Maternal iodine deficiency is related to high neonatal thyroid-stimulating hormone (TSH) values, with the threshold of 5 mIU/L recommended as an indicator of iodine nutrition status. The objective of this study was to analyse possible risk factors for increased TSH that could distort its validity as a marker of iodine status. The clinical relevance of this research question is that if the factors associated with iodine deficiency are known, iodine supplementation can be introduced in risk groups, both during pregnancy and in newborns.

METHODS

A case-control study was carried out in a sample of 46,622 newborns in 2002-2015 in Spain. Of these, 45,326 had a neonatal TSH value ≥5 mIU/L. The main variable was having TSH ≥5 mIU/L and the secondary variables were: sex, gestational age, day of sample extraction and maternal origin. Associated factors were analysed through a logistic regression model, calculating the odds ratio (OR).

RESULTS

The factors associated with this outcome were: male sex (OR = 1.34, 95% CI: 1.20-1.50, p<0.001), originating from an Asian/Oceanic country (OR = 0.80, 95% CI: 0.54-1.20, p = 0.536) or Europe (OR = 0.80, 95% CI: 0.66-0.96, p = 0.285) (including Spain, OR = 1) [p<0.001 for America (OR = 0.54, 95% CI: 0.44-0.68) and p = 0.025 for Africa (OR = 0.78, 95% CI: 0.62-0.97)] and fewer days from birth to sampling (OR = 0.80, 95% CI: 0.77-0.82, p<0.001).

CONCLUSIONS

The risk of high neonatal TSH without congenital hypothyroidism is higher in males, decreases with a greater number of days from birth to extraction, and is dependent on maternal ethnicity but not on gestational age.

Cystic Fibrosis

BACKGROUND

Universal screening of newborn babies for cystic fibrosis was launched in Germany on 1 September 2016. Here we present up-to-date information on the diagnosis, treatment, and prognosis of this disease.

METHODS

This article is based on relevant publications retrieved by a selective search in PubMed, along with guidelines from Germany and abroad and systematic reviews.

RESULTS

Cystic fibrosis is caused by a gene mutation leading to dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. It affects multiple organ systems-the lungs, pancreas, upper airways, liver, intestine, and reproductive organs-to varying degrees. Its incidence among newborn babies in Germany is between 1 in 3300 and 1 in 4800. Its diagnosis requires both clinical evidence (positive newborn screening, sibling[s] with cystic fibrosis, clinical signs) and the demonstration of CFTR dysfunction by an elevated chloride concentration in sweat, and/or two disease-causing mutations, and/or abnormal electrophysiological findings (nasal potential difference measurement, intestinal short-circuit current measurement). Patients should be cared for by specialized cystic fibrosis centers in close cooperation with their primary care physicians. The median life span of patients with this disease has risen steadily to the current value of 40 years. Aside from symptomatic treatment, the first mutation- specific treatments have recently become available.

CONCLUSION

Early diagnosis and optimized treatment prolong the lives of persons with cystic fibrosis and improve their quality of life. Causally directed treatment for all patients and their effects on the course of disease are now central issues for further research.

Metabolic screening and postnatal glucose homeostasis in the newborn

Although individual metabolic diseases are relatively uncommon, inherited metabolic diseases collectively represent a more common cause of disease in the neonatal period than is generally appreciated. Newborn screening is among the most successful public health programs today. Every day, newborns considered to be at risk for hypoglycemia are screened. The definition of clinically significant hypoglycemia remains among the most confused and contentious issues in neonatology. There are 2 "competing" methods of defining hypoglycemia that suggest very different levels for management: one based on metabolic-endocrinologic hormones and another that uses outcome data to determine threshold levels of risk.

Improving newborn screening for cystic fibrosis using next-generation sequencing technology: a technical feasibility study

PURPOSE

Many regions have implemented newborn screening (NBS) for cystic fibrosis (CF) using a limited panel of cystic fibrosis transmembrane regulator (CFTR) mutations after immunoreactive trypsinogen (IRT) analysis. We sought to assess the feasibility of further improving the screening using next-generation sequencing (NGS) technology.

METHODS

An NGS assay was used to detect 162 CFTR mutations/variants characterized by the CFTR2 project. We used 67 dried blood spots (DBSs) containing 48 distinct CFTR mutations to validate the assay. NGS assay was retrospectively performed on 165 CF screen-positive samples with one CFTR mutation.

RESULTS

The NGS assay was successfully performed using DNA isolated from DBSs, and it correctly detected all CFTR mutations in the validation. Among 165 screen-positive infants with one CFTR mutation, no additional disease-causing mutation was identified in 151 samples consistent with normal sweat tests. Five infants had a CF-causing mutation that was not included in this panel, and nine with two CF-causing mutations were identified.

CONCLUSION

The NGS assay was 100% concordant with traditional methods. Retrospective analysis results indicate an IRT/NGS screening algorithm would enable high sensitivity, better specificity and positive predictive value (PPV). This study lays the foundation for prospective studies and for introducing NGS in NBS laboratories.

Rectal prolapse and cystic fibrosis

Screening for cystic fibrosis (CF) is suggested in patients with rectal prolapse (RP). Little is known about the association between CF and RP in the era of newborn screening for CF. Our retrospective review showed that 3.6% of patients with RP had CF, and 3.5% of patients with CF had RP. No demographic or clinical factors appear to predict the likelihood of RP in patients with CF. Sweat chloride testing for patients with RP has a low yield in the era of newborn screening but may still need to be considered in children with RP to avoid missing the rare child with CF.

Differences in immunoreactive trypsin values between type of feeding and ethnicity in neonatal cystic fibrosis screening: a cross-sectional study

BACKGROUND

We studied the differences in immunoreactive trypsin (IRT) in neonatal screening for cystic fibrosis (CF) associated individually with the age of the newborn, ethnicity and environmental temperature. In this study, we determine the overall influence of environmental temperature at birth, gender, feeding, gestational age, maternal age and ethnic origin on an abnormal IRT result.

METHODS

Cross-sectional observational study. A sample was selected of newborns from Alicante (Spain) who underwent neonatal CF screening in 2012-2013. Primary variable: abnormal IRT levels (≥65 ng/ml). Secondary variables: gender, maternal origin, maternal age (years) (<20, 20-40, >40), gestational age (weeks) (<32, 32-37, >37), type of feeding (natural, formula, mixed and special nutrition), >20 days from birth to blood collection, and average temperature during the month of birth (in°C). Using a multivariate logistic regression model the adjusted odds ratios (ORs) were estimated to analyze the association between atypical IRT levels and the study variables. The α error was 5% and confidence intervals (CI) were calculated for the most relevant parameters.

RESULTS

Of a total of 13,310 samples, 199 were abnormal (1.34%). Significant associated factors: feeding method (natural → OR = 1; mixed → OR = 0.53, 95% CI: 0.31-0.89; formula → OR = 0.72, 95% CI: 0.48-1.07; special → OR = 21.88, 95% CI: 6.92-69.14; p < 0.001).

CONCLUSIONS

Newborns receiving special nutrition have a 20-fold higher risk for abnormal IRT levels, and screening is advisable once normalized feeding is initiated. It is advisable to consider ethnic variability. Seasonality was not important.

Diagnosis of cystic fibrosis in London and South East England before and after the introduction of newborn screening

INTRODUCTION

Newborn screening (NBS) for cystic fibrosis (CF) was introduced to London and South East England in 2007. We wished to assess the details of missed cases, and to compare the age at diagnosis and other clinical parameters, prescreening and postscreening.

METHODS

Retrospective and prospective case notes and database review of all newly diagnosed CF patients in our 7 CF centres, for 18 months before and 4 years after NBS started.

RESULTS

347 patients were diagnosed with CF. 126 patients were not screened (born before or abroad), and had a median age at diagnosis of 2.4 years, excluding those with meconium ileus (MI). Their median time to diagnosis from initial symptoms was 1 year, and in 10% it was >6 years. After NBS started, 170 were diagnosed by NBS (48% were already symptomatic); 7 moved into the region after NBS elsewhere; 34 presented with MI (6 were negative on NBS); and 10 screened children were missed (false negative cases). Median age of diagnosis was 3 weeks. Prevalence was 1 in 3991 live births. By 2 years of age (with data on 104 patients), 49 children (47%) had their first isolation of Pseudomonas aeruginosa, while 37 (36%) had their first growth of Staphylococcus aureus from respiratory cultures.

CONCLUSIONS

NBS has significantly reduced the age of diagnosis, although many were symptomatic even at 3 weeks of age. A small number of patients with CF can still be missed by the screening programme, and the diagnosis should be considered even with a negative screen result.

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.

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.

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.

Implementation of the first worldwide quality assurance program for cystic fibrosis multiple mutation detection in population-based screening

BACKGROUND

CDC's Newborn Screening Quality Assurance Program collaborated with several U.S. Cystic Fibrosis Care Centers to collect specimens for development of a molecular CFTR proficiency testing program using dried-blood spots for newborn screening laboratories.

METHODS

Adult and adolescent patients or carriers donated whole blood that was aliquoted onto filter paper cards. Five blind-coded specimens were sent to participating newborn screening laboratories quarterly. Proficiency testing results were evaluated based on presumptive clinical assessment. Individual evaluations and summary reports were sent to each participating laboratory and technical consultations were offered if incorrect assessments were reported.

RESULTS

The current CDC repository contains specimens with 39 different CFTR mutations. Up to 45 laboratories have participated in the program. Three years of data showed that correct assessments were reported 97.7% of the time overall when both mutations could be determined. Incorrect assessments that could have lead to a missed case occurred 0.9% of the time, and no information was reported 1.1% of the time due to sample failure.

CONCLUSIONS

Results show that laboratories using molecular assays to detect CFTR mutations are performing satisfactorily. The programmatic results presented demonstrate the importance and complexity of providing proficiency testing for DNA-based assays.

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.

Variation in immunoreactive trypsinogen concentrations among Michigan newborns and implications for cystic fibrosis newborn screening

OBJECTIVE

To investigate variation in immunoreactive trypsinogen (IRT) concentrations by race, sex, birth weight, and gestational age and their implications for the use of percentile-based cutoffs for cystic fibrosis (CF) newborn screening (NBS) programs.

PATIENTS AND METHODS

This cross-sectional population-based study of resident infants screened in Michigan investigates associations between demographic and perinatal variables and IRT concentrations after controlling for covariates. This study also analyzed how 96th and 99.8th IRT concentration percentiles values calculated by Michigan NBS vary by demographic and perinatal factors. Characteristics of infants having high (≥99.8th percentile) IRT concentrations and negative DNA tests are also explored.

RESULTS

IRT mean concentrations and percentiles vary significantly by race, birth weight, gestational age, and to a lesser degree by sex. The greatest variation in mean IRT concentrations was observed among racial categories; black infants had an adjusted mean concentration of 36 ng/ml and Asian/Pacific Islander infants had a mean concentration of 25 ng/ml compared to an average concentration of 28 ng/ml in white infants and infants of other races.

CONCLUSIONS

Variation in IRT concentrations resulted in the over-representation of certain groups referred for secondary testing, particularly referrals for sweat testing based on very high (≥99.8th percentile) concentrations alone, which is no longer recommended in Michigan. Further research may be warranted to evaluate initial IRT cutoffs used for CF NBS.

Newborn screening for cystic fibrosis

Newborn screening (NBS) for cystic fibrosis (CF) has evolved considerably from its beginnings. We review the early history of NBS in the USA and the evolution of CF NBS from its conception in observational studies, to the development of mass-screening methodology in the 1970s, and to its early applications in the USA and other countries. We review the development of current CF NBS algorithms, particularly the development of those used in the Wisconsin randomized controlled trial, and discuss the comparative utility of different algorithms. We also discuss the identified nutritional and respiratory benefits of CF NBS, discuss treatment strategies for newborns identified with CF, and also discuss opportunities for slowing the progression of this disease.

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.

Clinical practice and genetic counseling for cystic fibrosis and CFTR-related disorders

Cystic fibrosis transmembrane conductance regulator-related disorders encompass a disease spectrum from focal male reproductive tract involvement in congenital absence of the vas deferens to multiorgan involvement in classic cystic fibrosis. The reproductive, gastrointestinal, and exocrine manifestations of cystic fibrosis transmembrane conductance regulator deficiency are correlated with CFTR genotype, whereas the respiratory manifestations that are the main cause of morbidity and mortality in cystic fibrosis are less predictable. Molecular genetic testing of CFTR has led to new diagnostic strategies and will enable targeting of molecular therapies now in development. Older diagnostic methods that measure sweat chloride and nasal potential difference nonetheless remain important because of their sensitivity and specificity. In addition, the measurement of immunoreactive trypsinogen and the genotyping of CFTR alleles are key to newborn screening programs because of low cost. The multiorgan nature of cystic fibrosis leads to a heavy burden of care, thus therapeutic regimens are tailored to the specific manifestations present in each patient. The variability of cystic fibrosis lung disease and the variable expressivity of mild CFTR alleles complicate genetic counseling for this autosomal recessive disorder. Widespread implementation of newborn screening programs among populations with significant cystic fibrosis mutation carrier frequencies is expected to result in increasing demands on genetic counseling resources.

Newborn screening for cystic fibrosis

BACKGROUND

Does newborn screening for cystic fibrosis (CF) improve clinical outcomes, quality of life and survival?

OBJECTIVES

To examine whether newborn screening for CF prevents or reduces irreversible organ damage and improves clinical outcomes, quality of life and survival in people with CF without unacceptable adverse effects.

SEARCH STRATEGY

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from electronic database searches, handsearches of relevant journals and abstract books of conference proceedings.The Group's Trials Register last searched: June 2008.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials, published and unpublished, comparing screening to clinical diagnosis in people with CF.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility and quality and independently extracted data. Allocation concealment was unclear in both studies and sequence generation adequate in one.

MAIN RESULTS

Searches identified six trials. Two trials involving 1,124,483 neonates (210 with CF) with a maximum follow up of 17 years were eligible for inclusion. Varying study designs, outcomes reported and summary measures precluded calculation of pooled estimates and only data from one study were analysed. Severe malnutrition was less common among screened participants. Compared with screened participants, the odds ratio of weight below the tenth percentile was 4.12 (95% CI 1.64 to 10.38) and for height was 4.62 (95% CI 1.69 to 12.61) in the control group.At age seven, 88% of screened participants and 75% of controls had lung function parameters within normal limits of at least 89% predicted. At diagnosis chest radiograph scores were significantly better among screened participants; 33% of screened versus 50% of control participants had Wisconsin chest X-ray (WCXR) scores over five (P = 0.097) and 24% of screened versus 45% of control participants had Brasfield chest X-ray (BCXR) scores under 21 (P = 0.042)). Over time, chest radiograph scores were worse in the screened group (WCXR P = 0.017 and BCXR P = 0.041). Results were no longer significant after adjustment for genotype, pancreatic status, and Pseudomonas aeruginosa-culture results. In screened participants colonisation with Pseudomonas aeruginosa occurred earlier. Estimates suggest diagnosis through screening is less expensive.

AUTHORS' CONCLUSIONS

Two randomised controlled trials assessing neonatal screening in CF were identified; data from one study were included. Nutritional benefits are apparent. Screening provides potential for better pulmonary outcomes, but confounding factors influenced long-term pulmonary prognosis of people with CF. Screening seems less expensive than traditional diagnosis.

Elevated IRT levels in African-American infants: implications for newborn screening in an ethnically diverse population

During the first 4 years of newborn screening (NBS) for Cystic Fibrosis (CF) in New York there was a statistically significant, twofold greater relative risk of an Immunoreactive Trypsinogen (IRT) level greater than 95% in African-American infants. The reason for this previously reported increase in IRT level in African-American infants is unclear. The positive predictive value of a screen positive result in this population was only 0.3%. The bulk of screen-positive African-American infants were in the top 0.2% (IRT) group, with no CF mutations isolated. Repeat IRT testing at 2-3 weeks of age may represent a suitable approach to decrease the false-positive rate in this population.

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.

Newborn screening for cystic fibrosis: techniques and strategies

Newborn screening for cystic fibrosis has been carried out for over 25 years, and clinical and cost benefits have been documented. There is still much variation in the methods and strategies adopted. All current screening programmes use a measurement of immunoreactive trypsin as a primary screening test, and in most, a second tier test involves analysing DNA mutations. The choice of DNA mutations depends on the genetic background in the region, and considerations of cost. Using DNA analysis as part of a screening procedure has introduced unwanted carrier detection, and protocols have now been devised in an attempt to avoid this. There are at least seven distinct protocols in use, all of which have different advantages and disadvantages, and no method or strategy will suit every region. Further careful study of performance and costs of various strategies is needed.

Newborn screening for cystic fibrosis

Newborn screening for cystic fibrosis (CF) was considered over 3 decades ago in 1970; however, the technology did not exist then for an accurate neonatal screening test. With the development of immunoreactive trypsinogen analysis, alone or coupled with DNA mutation analysis, the means were developed for CF newborn screening. Studies have demonstrated benefits of newborn screening in the areas of nutrition, cognitive function, pulmonary function, and survival.

Guidelines for implementation of cystic fibrosis newborn screening programs: Cystic Fibrosis Foundation workshop report

Newborn screening for cystic fibrosis offers the opportunity for early intervention and improved outcomes. This summary, resulting from a workshop sponsored by the Cystic Fibrosis Foundation to facilitate implementation of widespread high quality cystic fibrosis newborn screening, outlines the steps necessary for success based on the experience of existing programs. Planning should begin with a workgroup composed of those who will be responsible for the success of the local program, typically including the state newborn screening program director and cystic fibrosis care center directors. The workgroup must develop a screening algorithm based on program resources and goals including mechanisms available for sample collection, regional demographics, the spectrum of cystic fibrosis disease to be detected, and acceptable failure rates of the screen. The workgroup must also ensure that all necessary guidelines and resources for screening, diagnosis, and care be in place prior to cystic fibrosis newborn screening implementation. These include educational materials for parents and primary care providers; systems for screening and for providing diagnostic testing and counseling for screen-positive infants and their families; and protocols for care of this unique population. This summary explores the benefits and risks of various screening algorithms, including complex situations that can occur involving unclear diagnostic results, and provides guidelines and sample materials for state newborn screening programs to develop and implement high quality screening for cystic fibrosis.

New York State cystic fibrosis consortium: the first 2.5 years of experience with cystic fibrosis newborn screening in an ethnically diverse population

OBJECTIVE

The purpose of this work was to report on the first 2.5 years of newborn screening for cystic fibrosis in New York.

METHODS

Directors of the 11 New York cystic fibrosis centers were asked to provide mutation data, demographic data, and selected laboratory results for each patient diagnosed by newborn screening and followed at their center. Summary data were also submitted from the New York newborn screening laboratory on the total number of patients screened, the number of positive screens, and the number of patients that were lost to follow-up. A second survey was submitted by each center regarding the availability of genetic counseling services at the center.

RESULTS

A total of 106 patients with cystic fibrosis were diagnosed through newborn screening in the first 2.5 years and followed at the 11 Cystic Fibrosis Foundation-sponsored cystic fibrosis care centers in New York. Two screen-negative infants were subsequently diagnosed with cystic fibrosis when symptoms developed. The allele frequency of deltaF508 was 57.4%, which is somewhat lower than the allele frequency of deltaF508 in the US cystic fibrosis population of 70%. There were 90 non-Hispanic white (84%), 12 Hispanic, 2 Asian, and 1 black infants diagnosed with cystic fibrosis during this period. Five patients were diagnosed secondary to a positive screen based on a high immunoreactive trypsinogen and no mutations.

CONCLUSIONS

Newborn screening for cystic fibrosis has been effectively conducted in New York using a unique screening algorithm that was designed to be inclusive of the diverse racial makeup of the state. However, this algorithm results in a high false-positive rate, and a large number of healthy newborns are referred for confirmatory sweat tests and genetic counseling. This experience indicates that it would be helpful to convene a working group of cystic fibrosis newborn screening specialists to evaluate which mutations should be included in a newborn screening panel.

The CF-CIRC study: a French collaborative study to assess the accuracy of cystic fibrosis diagnosis in neonatal screening

Background

Cystic fibrosis (CF) is caused by mutations in the gene encoding for the CF transmembrane conductance regulator (CFTR) protein, which acts as a chloride channel after activation by cyclic AMP (cAMP). Newborn screening programs for CF usually consist of an immunoreactive trypsinogen (IRT) assay, followed when IRT is elevated by testing for a panel of CF-causing mutations. Some children, however, may have persistent hypertrypsinogenemia, only one or no identified CFTR gene mutation, and sweat chloride concentrations close to normal values. In vivo demonstration of abnormal CFTR protein function would be an important diagnostic aid in this situation. Measurements of transepithelial nasal potential differences (NPD) in adults accurately characterize CFTR-related ion transport. The aim of the present study is to establish reference values for NPD measurements for healthy children and those with CF aged 3 months to 3 years, the age range of most difficult-to-diagnose patients with suspected CF. The ultimate goal of our study is to validate NPD testing as a diagnostic tool for children with borderline results in neonatal screening.

Methods/Design

We adapted the standard NPD protocol for young children, designed a special catheter for them, used a slower perfusion rate, and shortened the protocol to include only measurement of basal PD, transepithelial sodium (Na⁺) transport in response to the Na⁺ channel inhibitor amiloride, and CFTR-mediated chloride (Cl^-) secretion in response to isoproterenol, a β-agonist in a Cl^- free solution.

The study will include 20 children with CF and 20 healthy control children. CF children will be included only if they carry 2 CF-causing mutations in the CFTR gene or have sweat chloride concentrations > 60 mEq/L or both. The healthy children will be recruited among the siblings of the CF patients, after verification that they do not carry the familial mutation.

Discussion

A preliminary study of 3 adult control subjects and 4 children older than 12 years with CF verified that the new protocol was well tolerated and produced NPD measurements that did not differ significantly from those obtained with the standard protocol. This preliminary study will provide a basis for interpreting NPD measurements in patients with suspected CF after neonatal screening. Earlier definitive diagnosis should alleviate parental distress and allow earlier therapeutic intervention and genetic counseling.

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.

A survey of newborn screening for cystic fibrosis in Europe

BACKGROUND

Cystic fibrosis (CF) is a recessively inherited condition caused by mutation of the CFTR gene. Newborn infants with CF have raised levels of immuno-reactive trypsinogen (IRT) in their serum. Measurement of IRT in the first week of life has enabled CF to be incorporated into existing newborn screening (NBS) blood spot protocols. However, IRT is not a specific test for CF and NBS therefore requires a further tier of tests to avoid unnecessary referral for diagnostic testing. Following identification of the CFTR gene, DNA analysis for common CF-associated mutations has been increasingly used as a second tier test. The aim of this study was to survey the current practice of CF NBS programmes in Europe.

METHOD

A questionnaire was sent to 26 regional and national CF NBS programmes in Europe.

RESULTS

All programmes responded. The programmes varied in number of infants screened and in the protocols employed, ranging from sweat testing all infants with a raised first IRT to protocols with up to four tiers of testing. Three different assays for IRT were used; in the majority (24) this was a commercially available kit (Delfia). A number of programmes employed a second IRT measurement in the 4th week of life (as the IRT is more specific at this point). Nineteen programmes used DNA analysis for common CFTR mutations on samples with a raised first IRT. Three programmes used a second IRT measurement on infants with just one recognised mutation to reduce the number of infants referred for sweat testing. Referral to clinical services was prompt and diagnosis was confirmed by sweat testing, even in infants with two recognised mutations in most programmes. Subsequent clinical pathways were less uniform. Multivariate analysis demonstrated a relationship between the age of diagnosis and the timing of the first IRT. More sweat tests were undertaken if the first IRT was earlier and the diagnosis was later.

CONCLUSIONS

Annually these programmes screen approximately 1,600,000 newborns for CF and over 400 affected infants are recognised. The findings of this survey will guide the development of European evidence based guidelines and may help new regions or nations in the development and implementation of NBS for cystic fibrosis.

Newborn screening: complexities in universal genetic testing

Newborn screening (NBS)--in which each newborn infant is screened for up to 50 specific metabolic disorders for early detection and intervention--is the first program of populationwide genetic testing. As a public health intervention, NBS has greatly improved the lives of thousands of affected children. New technologies and new economic and social forces pose significant ethical and clinical challenges to NBS. Two primary challenges concern (1) accommodating clinical and ethical standards to rapid technological developments in NBS and (2) preparing public health systems to respond to the medical advances and social forces driving expansion of NBS programs. We describe and analyze these challenges through consideration of 3 disorders: phenylketonuria, medium-chain acyl-CoA dehydrogenase deficiency, and cystic fibrosis.

Markedly elevated neonatal immunoreactive trypsinogen levels in the absence of cystic fibrosis gene mutations is not an indication for further testing

AIMS

To investigate the immunoreactive trypsinogen (IRT) values above the usual 99th centile laboratory cut-off and determine the value of offering further testing to those infants with a markedly elevated IRT but no cystic fibrosis transmembrane regulator (CFTR) gene mutation identified by the screening programme.

METHODS

All babies born in Victoria, Australia, between 1991 and 2003, were screened by IRT followed by CF gene mutation analysis.

RESULTS

Of the 806,520 babies born, 9268 with the highest IRT levels had CFTR mutation analysis. There were 123 DeltaF508 homozygotes and 703 heterozygotes (86 with CF, 617 carriers). A total of 8442 babies had no CFTR gene mutation, of whom 18 (0.21%) had CF. The total number of CF babies with IRT greater than the laboratory cut-off was 227 (2.4%). The IRT results of the CF patients were distributed normally, with the majority above the laboratory cut-off of newborn IRT results. There was no evidence of an excess of babies with CF in the very highest levels of IRT above the 99th centile.

CONCLUSIONS

Only a small proportion of babies with a neonatal IRT >99th centile have CF. Additional CF testing for infants with an elevated IRT but no CFTR gene mutation has an extremely low yield, no matter how high the IRT result.

Pilot programs in newborn screening

The term "pilot study" has been used over the years to describe the evaluation of the many elements involved in deciding whether a proposed condition should be added to a newborn screening (NBS) panel, and until recently, was unilaterally used to describe the evaluation of the assay to be used before the condition was officially adopted by a state for its newborn screening panel. Since Guthrie's introduction of screening for PKU, each time a new condition was added to the panel, the screening assay itself was validated through a population-based trial, in which the test was performed with de-identified samples to avoid association between the test result and the infant. This is considered by the laboratory as the "pilot phase" of adding a new condition. To advance the science of NBS, especially to accommodate new technologies that may provide new types of information (genetic versus physiological) for each new condition, pilot programs are essential. Involvement of the clinical community serves to improve these evaluations and provides the needed clinical validation of decisions made as a result of it. This paper describes the historical context of pilot programs in population-based NBS that utilize laboratory-based markers as indicators of concern; specifically, three applications that demonstrate different approaches to the use of pilots in adding conditions to a NBS panel are described.

The clinical aspects of newborn screening: Importance of newborn screening follow-up

The aim of newborn screening is to identify presymptomatic healthy infants that will develop significant metabolic or endocrine derangements if left undiagnosed and untreated. The goal of ultimately reducing or eliminating irreversible sequelae is reached by maximizing test sensitivity of the primary newborn screening that measures specific analytes by a number of methodologies. Differentiation of true from false negatives is accomplished by the test specificity. This review discusses disorders for which, in general, there are available therapies and that are detected by routine and expanded newborn screening. Recommendations are presented for evaluation by a primary care physician, with confirmation by a metabolic or endocrinology specialist. Disorders are organized in tabular format by class of pathway or analyte, with attention to typical clinical presentations, confirmatory biochemical and molecular tests, and therapies. There are numerous challenges in clinical follow-up, including diagnosis and appropriate understanding of the consequences of the disorders. The data required to meet these challenges can be acquired only by large scale longitudinal comprehensive studies of outcome in children identified by newborn screening. Only with such data can newborn screening fully serve families.

Content of communication by pediatric residents after newborn genetic screening

BACKGROUND

Newborn screening saves lives, but psychosocial complications after genetic screening have led to doubts about expanding programs. Because complications have been blamed on ineffective communication of results, a population-scale system to ensure communication quality may improve outcomes. The objective of this study was to develop and evaluate a method to assess the content of communication after newborn genetic screening.

METHODS

We abstracted content data and calculated quantitative scores for 3 communication quality indicators (key content, early placement of good news, and excessive background content) for 59 transcribed conversations between pediatric residents and simulated parents of an "infant" who was found via newborn screening to carry either cystic fibrosis or sickle cell hemoglobinopathy.

RESULTS

Only 8.5% of transcripts contained the key content items that were thought to be necessary for parental understanding; 27.1% included reassuring news about carrier status within the first 10% of content. Scores for 3 quality indicators fell in the low performance range in 35.6%, 30.5%, and 27.1% of transcripts, respectively. The most common topic was background about the disease (22% of content statements) even though the infant did not have the disease. Surprisingly, 50% of sickle trait transcripts included counseling about a possible risk for sudden death.

CONCLUSIONS

Assessment of the content domain of communication quality identified some high-quality communication interspersed with many missed opportunities. If integrated into newborn screening, our method may help to alleviate some of society's ethical concerns about benefit and risk after newborn and other genetic screening.

Initially misleading communication of carrier results after newborn genetic screening

BACKGROUND

Newborn screening saves lives, but the way in which parents learn of a positive screening test is also important for adherence with treatment plans and avoidance of psychosocial complications. The first messages provided to parents may be particularly important for understanding, especially when the infant is found to be a heterozygous carrier for sickle cell hemoglobinopathy (SCH) or cystic fibrosis (CF). This study investigated the prevalence of "initially misleading" communication, defined as the inclusion of 1 of 55 "bad-news" content items (eg, the screening test is positive) before any of 39 "good-news" content items (eg, the infant is healthy, normal, a carrier, or otherwise without problems).

METHODS

As part of a larger study of the content of counseling after newborn genetic screening, we used a quantitative, explicit-criteria method to abstract 59 transcribed conversations between pediatric residents and standardized parents of an "infant" who was found through newborn screening to carry either CF or SCH.

RESULTS

Of 59 transcripts, 41 were found to be misleading (at least 1 bad-news content statement before the first good-news content statement). There were significantly more misleading likely-CF-carrier than SCH-carrier transcripts (89.7% vs 50%). Among the misleading transcripts, the mean number of misleading statements was 5.5. The mean distance between the first bad-news and first good-news statements was 28.1 statements (20.5% of the total duration of counseling).

DISCUSSION

The high prevalence of misleading content and the time lag before clarification does not bode well for parental understanding of infant carrier status. Future projects should improve curricula for training programs and develop quality-assurance efforts for community clinicians both to improve parental understanding and help assuage society's fears about the safety of genetic screening technologies.

Potential costs and benefits of newborn screening for severe combined immunodeficiency

OBJECTIVE

Severe combined immunodeficiency (SCID) is a rare, treatable disorder of the immune system. The incidence is unknown but may be more common than published estimates because infants frequently die of infection before diagnosis. SCID is a candidate for universal newborn screening, so there is a need to determine under which circumstances screening would be cost-effective.

STUDY DESIGN

We assumed a screening program for SCID would use T-cell lymphopenia as the screening criterion and performed a cost-utility analysis comparing universal screening with screening only those with a family history of SCID.

RESULTS

Assuming society is willing to pay $50,000 for every quality-adjusted life-year saved, a SCID screening test that cost less than $5 with a false-negative rate of 0.9% and a false-positive rate of 0.4% would be considered cost-effective. A nationwide screening program would cost an additional $23.9 million per year for screening costs but would result in 760 years of life saved per year of screening. The cost to detect 1 case of SCID would be $485,000.

CONCLUSION

SCID screening could result in a large benefit to detected individuals, making screening relatively cost-effective in spite of the low incidence of the disease. However, an adequate test is critical to cost-effectiveness.

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.

Newborn screening for cystic fibrosis in Wisconsin: nine-year experience with routine trypsinogen/DNA testing

OBJECTIVE

To describe the development and follow-up confirmatory results of the routine cystic fibrosis (CF) newborn screening (NBS) program in Wisconsin.

METHODS

CF NBS has been performed on a routine clinical basis in Wisconsin since July 1994. The 2-tiered immunoreactive trypsinogen (IRT)/DNA technique was used on dried blood on filter paper spots. From July 1994 to February 2002, mutation analysis was for the DeltaF508 allele. Beginning in March 2002, multimutation analysis of 25 CF mutations was performed. Infants with a positive result on NBS were seen in certified CF centers for sweat testing by means of quantitative pilocarpine iontophoresis, and families received genetic counseling.

RESULTS

From July 1994 to February 2002, there were 120 cases of CF detected by means of NBS (509,794 infants screened), with 53 DeltaF508 homozygotes and 67 compound heterozygotes. There were 8 clinically diagnosed cases of CF (no DeltaF508 allele). The CF incidence was 1:3983 (95%CI, 1:3373-1:4774). From March 2002 to June 2003, multimutation analysis identified 21 cases of classic CF (90,142 infants screened). Sweat tests were successfully performed in infants younger than 1 month.

CONCLUSIONS

Early diagnosis of CF through NBS was successfully performed, with an estimated sensitivity rate of 99% using the IRT/25 CFTR multimutation assay.

Information flow after a positive newborn screening for cystic fibrosis

OBJECTIVES

To provide a model of the information processes instigated by a positive result on a newborn screening for cystic fibrosis and to analyze their implications for future research.

METHOD

We reviewed research conducted at Wisconsin and elsewhere.

RESULTS

We identified 6 distinct phases of information flow.

CONCLUSION

Although continued attention to genetic counseling is clearly warranted, research on information flow after newborn screening should: 1) look beyond genetic counseling to include a variety of information sources including family, friends, and the Internet; 2) appreciate that families vary in their willingness to acquire cystic fibrosis-related information; and 3) should seek to better understand how this information moves through social networks.

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.

Risk calculations for cystic fibrosis in neonatal screening by immunoreactive trypsinogen and CFTR mutation tests

PURPOSE

Although neonatal screening (or newborn screening) for cystic fibrosis (CF) is commonly practiced, systematic methods for accurate risk calculations are currently lacking.

METHODS AND RESULTS

We evaluated characteristics of the immunoreactive trypsinogen (IRT) test using the published data. The probability that a neonate has a positive IRT test, if the neonate is affected, a carrier, or a noncarrier, is approximately 1, 0.041, or 0.011, respectively. We provide methods to calculate genetic risks for a variety of commonly encountered scenarios in which neonates are positive by the IRT test.

CONCLUSION

Our Bayesian methods permit CF disease probabilities to be calculated accurately, taking into account all relevant information.