Initial evaluation of a biochemical cystic fibrosis newborn screening by sequential analysis of immunoreactive trypsinogen and pancreatitis-associated protein (IRT/PAP) as a strategy that does not involve DNA testing in a Northern European population

Wilson and Jungner Revisited: Are Screening Criteria Fit for the 21st Century?

Driven by technological innovations, newborn screening (NBS) panels have been expanded and the development of genomic NBS pilot programs is rapidly progressing. Decisions on disease selection for NBS are still based on the Wilson and Jungner (WJ) criteria published in 1968. Despite this uniform reference, interpretation of the WJ criteria and actual disease selection for NBS programs are highly variable. A systematic literature search [PubMED search "Wilson" AND "Jungner"; last search 16.07.22] was performed to evaluate the applicability of the WJ criteria for current and future NBS programs and the need for adaptation. By at least two reviewers, 105 publications (systematic literature search, N = 77; manual search, N = 28) were screened for relevant content and, finally, 38 publications were evaluated. Limited by the study design of qualitative text analysis, no statistical evaluation was performed, but a structured collection of reported aspects of criticism and proposed improvements was instead collated. This revealed a set of general limitations of the WJ criteria, such as imprecise terminology, lack of measurability and objectivity, missing pediatric focus, and absent guidance on program management. Furthermore, it unraveled specific aspects of criticism on clinical, diagnostic, therapeutic, and economical aspects. A major obstacle was found to be the incompletely understood natural history and phenotypic diversity of rare diseases prior to NBS implementation, resulting in uncertainty about case definition, risk stratification, and indications for treatment. This gap could be closed through the systematic collection and evaluation of real-world evidence on the quality, safety, and (cost-)effectiveness of NBS, as well as the long-term benefits experienced by screened individuals. An integrated NBS public health program that is designed to continuously learn would fulfil these requirements, and a multi-dimensional framework for future NBS programs integrating medical, ethical, legal, and societal perspectives is overdue.

Single-centre prospective evaluation of the first 5 years of cystic fibrosis newborn screening in Germany

Background

In 2016, nationwide cystic fibrosis newborn screening (CFNS) was newly implemented in Germany, using an immunoreactive trypsin/pancreatitis-associated protein/DNA screening algorithm that differs from most other nationwide screening programmes.

Methods

We analysed real-life feasibility of the confirmation process with respect to our pre-specified procedural objectives. These included overall accuracy through false-negative and false-positive results, effectiveness of the Bavarian tracking system, and accuracy of Macroduct and Nanoduct sweat conductivity compared with quantitative chloride determination. All consecutive CFNS-positive newborns assigned to our CF centre and born between 1 September 2016 and 31 August 2021 (n=162) were included.

Results

The German CFNS was feasible at our CF centre as all procedural objectives were met. The positive predictive value (PPV) of positive CFNS was low (0.23) and two initially negatively screened children were later diagnosed with CF. The tracking system was highly efficient with a 100% tracking rate. The Macroduct and Nanoduct systems had comparable success rates (93.2% versus 95.9%). Importantly, conductivity via Macroduct was more accurate than via Nanoduct (zero and four false-positive newborns, respectively).

Conclusions

CF confirmation diagnostics of neonates in a certified regional CF centre was well managed in daily routine. The PPV of the German CFNS needs to be improved, e.g. by extending the DNA analysis within the screening algorithm and by increasing the number of variants tested. The Bavarian tracking system can serve as a successful model for other tracking systems. We preferred the Macroduct system because of its more accurate sweat conductivity readings.

Influence of Season, Storage Temperature and Time of Sample Collection in Pancreatitis-Associated Protein-Based Algorithms for Newborn Screening for Cystic Fibrosis

Newborn screening (NBS) for cystic fibrosis (CF) based on pancreatitis-associated protein (PAP) has been performed for several years. While some influencing factors are known, there is currently a lack of information on the influence of seasonal temperature on PAP determination or on the course of PAP blood concentration in infants during the first year of life. Using data from two PAP studies at the Heidelberg NBS centre and storage experiments, we compared PAP determinations in summer and winter and determined the direct influence of temperature. In addition, PAP concentrations measured in CF-NBS, between days 21-35 and 36-365, were compared. Over a 7-year period, we found no significant differences between PAP concentrations determined in summer or winter. We also found no differences in PAP determination after 8 days of storage at 4 °C, room temperature or 37 °C. When stored for up to 3 months, PAP samples remained stable at 4 °C, but not at room temperature (p = 0.007). After birth, PAP in neonatal blood showed a significant increasing trend up to the 96th hour of life (p < 0.0001). During the first year of life, blood PAP concentrations continued to increase in both CF- (36-72 h vs. 36-365 d p < 0.0001) and non-CF infants (36-72 h vs. 36-365 d p < 0.0001). Seasonal effects in central Europe appear to have a limited impact on PAP determination. The impact of the increase in blood PAP during the critical period for CF-NBS and beyond on the applicability and performance of PAP-based CF-NBS algorithms needs to be re-discussed.

German newborn screening for Cystic fibrosis: Parental perspectives and suggestions for improvements

PURPOSE

Cystic fibrosis (CF) was added to the German newborn bloodspot screening (NBS) panel in 2016. This study assesses parental perceptions of CF-NBS and confirmatory testing.

METHODS

Prospective questionnaire-based survey administered to parents of children with positive CF-NBS over 40 months after initiation of CF-NBS in Southwest Germany. Parental perceptions were compared to results from Bavaria and Switzerland.

RESULTS

Questionnaires with 29 standardized questions were sent to 343 families with children born between October 2016 and January 2020. A total of 178 (51.9%) replied. Although required by law, only a minority were informed about CF-NBS by a physician. The information provided about NBS was sufficient for 78% of parents. Regarding the information about positive CF-NBS, 52.9% were satisfied but the majority expressed negative emotions (89.5%). While most of these were resolved after confirmatory diagnostics, 17% of parents of children with false-positive CF-NBS and 66.7% of children confirmed with CF remained anxious. Waiting time for sweat testing was >3 days in 56.1%, considerably longer than in more centralized screening systems. Parents who waited for a maximum of 3 days were significantly more satisfied. 70.7% of parents were satisfied with the information given during confirmatory diagnostics and 91.4% were satisfied with participating in CF-NBS.

CONCLUSIONS

CF-NBS stands in high regard with parents. Smooth organization, timely initiation of confirmatory testing, and professional communication are most important to limit parental anxiety. A more centralized system of confirmatory diagnostics appears advantageous in several regards as it reduces time from positive NBS to final diagnosis and increases parental satisfaction.

[Update on cystic fibrosis : From neonatal screening to causal treatment]

Cystic fibrosis (CF) is a multiorgan disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Approximately 90% of the morbidity and mortality are caused by pulmonary involvement. The mean life expectancy of patients with CF in 2020 was more than 52 years in Germany. The introduction of neonatal screening for CF and the development of a causally acting CFTR modulator treatment have clearly improved the prognosis of these patients. As an introduction, this article describes important aspects of CF in this context in order to go into details of the CF neonatal screening which was introduced in Germany in 2016.

Final results of the southwest German pilot study on cystic fibrosis newborn screening - Evaluation of an IRT/PAP protocol with IRT-dependent safety net: Results of the Southwest German CFNBS pilot study

BACKGROUND

Previous studies suggest that PAP-based CF protocols are suitable for newborn screening (NBS) for cystic fibrosis (CF) when newborns designated as CFSPID should not be detected. However, there are still discussions about the performance of IRT/PAP algorithms. We present the final results of a pilot study evaluating a IRT/PAP protocol with an IRT-dependent safety net (SN) conducted from 2008 to 2016 in southwestern Germany on nearly 500,000 newborns.

METHODS

To achieve reliable data, all newborns were screened using both the PAP-based and a DNA-based CFNBS algorithm. PAP quantification and genetic analysis of the four most common CFTR mutations in Germany were performed in all newborns with IRT≥99.0 percentile. NBS was rated positive if either PAP was ≥1.6 µg/l and/or at least one CFTR mutation was detected. In addition, an IRT-dependent SN resulted in positive rating for both protocols if IRT was ≥99.9 percentile. To evaluate the IRT/PAP protocol, its performance was compared to that of the IRT/DNA protocol.

RESULTS

The IRT/PAP protocol with IRT-based SN used in the study achieved a sensitivity of 94%, if false-negative detected neonates with meconium ileus and those designated as CFSPID were excluded from analysis. CF/CFSPID ratio was 92. However, PPV of the IRT/PAP+SN protocol was with 10.3% very low.

CONCLUSIONS

PAP-based CFNBS protocols can be used, if less detection of CFSPID is desired. The IRT/PAP protocol with IRT-dependent SN evaluated here achieved adequate sensitivity but should probably be used in combination with a third-tier test to also achieve an acceptable PPV.

Magnetic Resonance Imaging Detects Progression of Lung Disease and Impact of Newborn Screening in Preschool Children with Cystic Fibrosis

RATIONALE

Previous cross-sectional studies demonstrated that chest magnetic resonance imaging (MRI) is sensitive to detect early lung disease in infants and preschool children with cystic fibrosis (CF) without radiation exposure. However, the ability of MRI to detect progression of lung disease and the impact of early diagnosis in preschool children with CF remains unknown.

OBJECTIVES

To investigate the potential of MRI to detect progression of early lung disease and impact of early diagnosis by CF newborn screening (NBS) in preschool children with CF.

METHODS

Annual MRI was performed from diagnosis over four years in a cohort of 96 preschool children with CF (age 0-4 yr) that were concurrently diagnosed based on NBS (n=28) or clinical symptoms (n=68). MRI scans were evaluated using a dedicated morphofunctional score and the relationship between longitudinal MRI scores and respiratory symptoms, pulmonary exacerbations, upper airway microbiology and mode of diagnosis were determined.

MEASUREMENTS AND MAIN RESULTS

The MRI global score increased in the total cohort of children with CF during preschool years (P<0.001) which was associated with cough, pulmonary exacerbations (P<0.0001), and detection of Staphylococcus aureus and Haemophilus influenzae (P<0.05). MRI-defined abnormalities in lung morphology, especially airway wall thickening/bronchiectasis, were lower in NBS compared to clinically diagnosed children with CF throughout the observation period (P<0.01).

CONCLUSIONS

MRI detected progression of early lung disease and benefits of early diagnosis by NBS in preschool children with CF. These findings support MRI as sensitive outcome measure for diagnostic monitoring and early intervention trials in preschool children with CF.

Potential of Intestinal Current Measurement for Personalized Treatment of Patients with Cystic Fibrosis

Refinement of personalized treatment of cystic fibrosis (CF) with emerging medicines targeting the CF basic defect will likely benefit from biomarkers sensitive to detect improvement of cystic fibrosis transmembrane conductance regulator (CFTR) function in individual patients. Intestinal current measurement (ICM) is a technique that enables quantitative assessment of CFTR chloride channel function in rectal tissues or other intestinal epithelia. ICM was originally developed to study the CF ion transport defect in the intestine and has been established as a sensitive biomarker of CFTR function and diagnostic test for CF. With the emergence of CFTR-directed therapeutics, ICM has become an important tool to estimate the level of rescue of CFTR function achieved by approved CFTR modulators, both at the level of CFTR genotype groups, as well as individual patients with CF. In combination with preclinical patient-derived cell culture models, ICM may aid the development of targeted therapies for patients with rare CFTR mutations. Here, we review the principles of ICM and examine how this CFTR biomarker may be used to support diagnostic testing and enhance personalized medicine for individual patients with common as well as rare CFTR mutations in the new era of medicines targeting the underlying cause of CF.

Comparison between two newborn screening strategies for cystic fibrosis in Argentina: IRT/IRT versus IRT/PAP

BACKGROUND

The benefits of early cystic fibrosis (CF) detection using newborn screening (NBS) has led to widespread use in NBS programs. Since 2002, a two-stage immunoreactive trypsinogen (IRT/IRT) screening strategy has been used as a CFNBS method in all public maternity units in the City of Buenos Aires, Argentina. However, novel screening strategies may be more efficient. The aim of this study is to prospectively compare two CFNBS strategies: IRT/IRT and IRT/PAP (pancreatitis-associated protein).

METHODS

A two-year prospective study was performed. IRT was measured in dried blood samples collected 48-72 h after birth. When an IRT value was abnormal, PAP was determined, and a second visit was scheduled to obtain another sample for IRT before 25 days of life. Newborns with a positive CFNBS were referred for a confirmatory sweat test.

RESULTS

There were 69,827 births in the City of Buenos Aires during the period studied; 918 (1.31%) had an abnormal IRT. A total of 207 children (22.5%) failed to return for the second IRT, but only two PAP (0.2%) were not performed. IRT/IRT was more likely to lead to a referral for sweat testing than IRT/PAP (odds ratio 2.3 [95% confidence interval 1.8-2.9], p < .001). Sensitivity and specificity were: 80% and 100% and 86.5% and 82.6% for IRT/IRT and IRT/PAP strategies, respectively.

CONCLUSION

The IRT/PAP strategy is more sensitive than IRT/IRT and has similar specificity; it avoids a second visit and unnecessary sweat testing, and it reduces loss to follow-up in our population.

Pancreatitis-Associated Protein in Neonatal Screening for Cystic Fibrosis: Strengths and Weaknesses

There are currently four countries and one local region in Europe that use PAP in their newborn screening programme. The first country to employ PAP at a national level was the Netherlands, which started using IRT/PAP/DNA/EGA in 2011. Germany followed in 2016 with a slightly different IRT/PAP/DNA strategy. Portugal also started in 2016, but with an IRT/PAP/IRT programme, and in 2017, Austria changed its IRT/IRT protocol to an IRT/PAP/IRT program. In 2018, Catalonia started to use an IRT/PAP/IRT/DNA strategy. The strengths of PAP are the avoidance of carrier detection and a lower detection rate of CFSPID. PAP seems to have advantages in detecting CF in ethnically-diverse populations, as it is a biochemical approach to screening, which looks for pancreatic injury. Compared to an IRT/IRT protocol, an IRT/PAP protocol leads to earlier diagnoses. While PAP can be assessed with the same screening card as the first IRT, the second IRT in an IRT/IRT protocol requires a second heel prick around the 21st day of the patient's life. However, IRT/PAP has two main weaknesses. First, an IRT/PAP protocol seems to have a lower sensitivity compared to a well-functioning IRT/DNA protocol, and second, IRT/PAP that is performed as a purely biochemical protocol has a very low positive predictive value. However, if the advantages of PAP are to be exploited, a combination of IRT/PAP with genetic screening or a second IRT as a third tier could be an alternative for a sufficiently performing CF-NBS protocol.

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

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

Cystic Fibrosis Newborn Screening in Portugal: PAP Value in Populations with Stringent Rules for Genetic Studies

Newborn screening (NBS) for cystic fibrosis (CF) has been shown to be advantageous for children with CF, and has thus been included in most NBS programs using various algorithms. With this study, we intend to establish the most appropriate algorithm for CF-NBS in the Portuguese population, to determine the incidence, and to contribute to elucidating the genetic epidemiology of CF in Portugal. This was a nationwide three-year pilot study including 255,000 newborns (NB) that were also screened for congenital hypothyroidism (CH) and 24 other metabolic disorders included in the Portuguese screening program. Most samples were collected in local health centers spread all over the country, between the 3rd and 6th days of life. The algorithm tested includes immunoreactive trypsinogen (IRT) determination, pancreatitis associated protein (PAP) as a second tier, and genetic study for cases referred to specialized clinical centers. Thirty-four CF cases were confirmed positive, thus indicating an incidence of 1:7500 NB. The p.F508del mutation was found in 79% of the alleles. According to the results presented here, CF-NBS is recommended to be included in the Portuguese NBS panel with a small adjustment regarding the PAP cut-off, which we expect to contribute to the improvement of the CF-NBS performance. According to our results, this algorithm is a valuable alternative for CF-NBS in populations with stringent rules for genetic studies.

Results of the Andalusian Cystic Fibrosis Neonatal Screening Program, 5 Years After Implementation

INTRODUCTION

Cystic fibrosis neonatal screening (CFNS), based on double determination of immunoreactive trypsinogen ([IRT] [IRT1/IRT2]), has been available in Andalusia since May 2011. If screening is positive, a sweat test is performed, and if that is positive or inconclusive, genetic testing is requested.

OBJECTIVE

To analyze CFNS, based on results from the first 4.5 years of the program.

MATERIALS AND METHODS

Prospective descriptive study of neonates undergoing CFNS. IRT levels, sweat chloride, and mutations were recorded. Statistical analysis was performed using SPSS 12.0.

RESULTS

Between May 2011 and December 2016, 474,953 neonates underwent CFNS. Of these, 1,087 (0.23%) had elevated IRT2. Since CFNS was introduced, 73 cases of cystic fibrosis were diagnosed; 60 were diagnosed by positive CFNS, and 13 were diagnosed by other means. In one case, the patient developed a typical clinical picture of cystic fibrosis, but had not undergone CFNS at the decision of the parents; the remaining 12 had a negative CFNS (false negatives). Of these, one patient was diagnosed before symptoms developed, as his twin brother had a positive CFNS result; another had chloride at the upper limit of normal, and was subsequently diagnosed with genetic testing before symptoms appeared; and 10 patients developed clinical signs and symptoms. Excluding patients with meconium ileus, sensitivity and specificity of the CFNS program were 85.71% and 99.78%, respectively. The incidence of the disease in Andalusia is 1/6,506 live births.

CONCLUSION

These results are a basis for reflection on possible areas for improvement of the CFNS algorithm, and thought may be given to the introduction of genetic studies to increase sensitivity and reduce false positives.

Diagnostic Testing in Cystic Fibrosis

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

PAP assays in newborn screening for cystic fibrosis: a population-based cost-effectiveness study

Objectives

To compare the cost effectiveness of adding a pancreatitis-associated protein (PAP) assay to common immunoreactive trypsinogen (IRT) and DNA cystic fibrosis (CF) newborn screening strategies.

Methods

Using data collected on 553,167 newborns, PAP cut-offs were calculated based on non-inferiority of the detection rates of classical forms of CF. Cost effectiveness was considered from the third-party payer's perspective using only direct medical costs, and the unit costs of PAP assays were assessed based on a micro-costing study. Robustness of the cost-effectiveness estimates was assessed, taking the secondary outcomes of screening (ie. detecting mild forms and CF carriers) into account.

Results

IRT/DNA, IRT/PAP, and IRT/PAP/DNA strategies had similar detection rates for classical forms of CF, but the strategies involving PAP assays detected smaller numbers of mild forms of CF. The IRT/PAP strategy was cost-effective in comparison with either IRT/DNA or IRT/PAP/DNA. IRT/PAP/DNA screening was cost-effective in comparison with IRT/DNA if relatively low value was assumed to be attached to the identification of CF carriers.

Conclusions

IRT/PAP strategies could be strictly cost-effective, but dropping DNA would mean the test could not detect CF carriers. IRT/PAP/DNA strategies could be a viable option as they are significantly less costly than IRT/DNA, but still allow CF carrier detection.

Five years of experience with biochemical cystic fibrosis newborn screening based on IRT/PAP in Germany

BACKGROUND

Evidence from recent studies suggests that IRT/PAP protocols may be successfully used as a purely biochemical newborn screening (NBS) for cystic fibrosis (CF) that does not require genetic screening. However, the experience with the performance of different IRT/PAP protocols remains limited. In this study, we evaluated the performance of IRT/PAP-based CF-NBS used in two German regions between 2008 and 2013 in a large cohort.

METHODS

In both regions slightly different IRT/PAP protocols were used to screen newborns for CF. In contrast to the original IRT/PAP protocol published by Sarles et al., both German protocols contained an IRT-dependent safety net strategy (CF-NBS positive, if IRT≥99.9th percentile). Positive rating of the screening result led to confirmatory diagnostics using sweat chloride testing and clinical assessment.

FINDINGS

A total of 328,181 newborns were tested with IRT/PAP in Germany within 5 years. 639 of these newborns (0.19%) were tested positive, and 60 infants were diagnosed with CF leading to a sensitivity of 0.968 and a PPV (positive predictive value) of 0.097. Compared to IRT/DNA protocols, the PPV of IRT/PAP is lower, but PAP used as second tier test has the advantage of a lower detection rate of healthy carriers and CF patients with equivocal results.

CONCLUSIONS

Our results obtained in a large cohort of ∼330,000 newborns support the use of a purely biochemical IRT/PAP protocol as an acceptable alternative when genetic CF-NBS has to be avoided.

Different Viewpoints: International Perspectives on Newborn Screening

Newborn blood-spot screening to detect potentially treatable disorders is widely practiced across the globe. However, there are great variations in practice, both in terms of disorders covered, screening technologies, disease definition, information provision, parental informed consent, and storage and disposal of residual specimens, partly reflecting the degree to which screening is the subject of explicit legislation (and thus public and media pressure) or is embedded in a general health care system and managed at an executive level. It is generally accepted that disorders to be screened for should comply with the ten Wilson and Jungner criteria, but the way that compliance is assessed ranges from broadly-based opinion surveys to detailed analysis of quantitative data. Consequently, even countries with comparable levels of economic development and health care show large differences in the number of disorders screened for. There are several areas on which there are no generally accepted guidelines: how should parents be informed about screening and to what extent should they be encouraged to regard screening as an option to choose to refuse? Is DNA mutation analysis acceptable as part of a screening protocol? How soon should the blood samples be destroyed once screening has been completed? As technology advances and the potential scope of screening expands at both the metabolite and genome level, challenging policy issues will have to be faced.

Austrian Newborn Screening Program: a perspective of five decades

In 1966, the National Austrian Newborn Screening Program for inherited metabolic and endocrine disorders was initiated. In the last five decades, around four million babies were screened and in more than 2600 babies, various inborn errors of metabolism and endocrine disorders were detected. This health-preventive program was continuously expanded from phenylketonuria and galactosemia to congenital hypothyroidism, biotinidase deficiency, cystic fibrosis, and congenital adrenal hyperplasia. In 2002, the introduction of tandem mass spectrometry substantially increased the number of detectable rare diseases, and now includes disorders of fatty acid oxidation, organic acidurias, and various disorders of amino acid metabolism. In this review, we highlight the development of the Austrian screening program, and pinpoint future disorders and challenges.

Comparison of different IRT-PAP protocols to screen newborns for cystic fibrosis in three central European populations

BACKGROUND

In recent years different IRT/PAP protocols have been evaluated, but the individual performance remains unclear. To optimize the IRT/PAP strategy we compared protocols from three regional CF newborn screening centers (Heidelberg, Dresden, and Prague).

METHODS

We evaluated the effect of elevating the IRT-cut-off from 50 to 65 μg/l (~97.5th to ~99.0th percentile), the need of a failsafe protocol (FS, IRT ≥ 99.9th percentile) and the relative performance using either two IRT-dependent PAP-cut-offs or one PAP-cut-off.

FINDINGS

Elevation of the IRT cut-off to 65 μg/l (~99.0th percentile) increased the PPV significantly (Dresden: 0.065 vs. 0.080, p < 0.0001, Prague: 0.052 vs. 0.074, p < 0.0001) without reducing sensitivity. All three IRT/PAP protocols showed a trend towards a higher sensitivity with FS than without and when using one PAP-cut-off instead of two IRT-dependent PAP-cut-offs.

CONCLUSIONS

For best performance we suggest an IRT/PAP protocol with an IRT-cut-off close to the 99.0th percentile, FS, and a single PAP-cut-off.

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.

Prospective and parallel assessments of cystic fibrosis newborn screening protocols in the Czech Republic: IRT/DNA/IRT versus IRT/PAP and IRT/PAP/DNA

Cystic fibrosis (CF) is a life-threatening disease for which early diagnosis following newborn screening (NBS) improves the prognosis. We performed a prospective assessment of the immunoreactive trypsinogen (IRT)/DNA/IRT protocol currently in use nationwide, versus the IRT/pancreatitis-associated protein (PAP) and IRT/PAP/DNA CF NBS protocols. Dried blood spots (DBS) from 106,522 Czech newborns were examined for IRT concentrations. In the IRT/DNA/IRT protocol, DNA-testing was performed for IRT ≥ 65 ng/mL. Newborns with IRT ≥ 200 ng/mL and no detected cystic fibrosis transmembrane conductance regulator gene (CFTR) mutations were recalled for a repeat IRT. In the same group of newborns, for both parallel protocols, PAP was measured in DBS with IRT ≥ 50 ng/mL. In PAP-positive newborns (i.e., ≥1.8 if IRT 50-99.9 or ≥1.0 if IRT ≥ 100, all in ng/mL), DNA-testing followed as part of the IRT/PAP/DNA protocol. Newborns with at least one CFTR mutation in the IRT/DNA/IRT and IRT/PAP/DNA protocols; a positive PAP in IRT/PAP; or a high repeat IRT in IRT/DNA/IRT were referred for sweat testing.

CONCLUSION

the combined results of the utilized protocols led to the detection of 21 CF patients, 19 of which were identified using the IRT/DNA/IRT protocol, 16 using IRT/PAP, and 15 using IRT/PAP/DNA. Decreased cut-offs for PAP within the IRT/PAP protocol would lead to higher sensitivity but would increase false positives. Within the IRT/PAP/DNA protocol, decreased PAP cut-offs would result in high sensitivity, an acceptable number of false positives, and would reduce the number of DNA analyses. Thus, we concluded that the IRT/PAP/DNA protocol would represent the most suitable protocol in our conditions.

Improving test properties for neonatal cystic fibrosis screening in the Netherlands before the nationwide start by May 1st 2011

When new technical possibilities arise in health care, often attunement is needed between different actors from the perspectives of research, health care providers, patients, ethics and policy. For cystic fibrosis (CF) such a process of attunement in the Netherlands started in a committee of the Health Council on neonatal screening in 2005. In the balancing of pros and cons according to Wilson and Jungner criteria, the advantages for the CF patient were considered clear, even though CF remains a severe health problem with treatment. Nevertheless, screening was not started then, mainly since the specificity of the tests available at that time was considered too low. Many healthy infants would have been referred for sweat testing and much uncertainty would arise in their parents. Also the limited sensitivity for immigrants and the detection of less severe phenotypes and carriers were considered problematic. The Health Council recommended a pilot screening project which was subsequently performed in some provinces, leading to a 4-step protocol: IRT, PAP, screening for a CFTR mutation panel, and sequencing of the CFTR gene. This would lead to the identification of 23 cases of classical CF, two infants with less severe forms and 12 carriers per year in the Netherlands. Thus many CF patients can be diagnosed early, while limiting the number of referrals, the number of infants with less severe forms diagnosed and the number of carriers identified. Technical solutions were found to limit the ethical problems. A nationwide program using this four step protocol started by 1 May 2011.

Newborn screening for cystic fibrosis

PURPOSE OF REVIEW

Newborn screening for cystic fibrosis (CF) is now universal in the US and many other countries. The rapid expansion of screening has resulted in numerous publications identifying new challenges for healthcare providers. This review provides an overview of these publications and includes ideas on managing these challenges.

RECENT FINDINGS

Most CF newborn screening algorithms involve DNA mutation analysis. As screening has expanded, new challenges have been identified related to carrier detection and inconclusive diagnoses. Early descriptions of infants with CF-related metabolic syndrome (CRMS) indicate that the natural history of this condition cannot be predicted. Early identification has also provided an opportunity to better understand the pathophysiology of CF. However, few studies have been conducted in infants with CF to determine optimal therapy and recommendations are largely anecdotal.

SUMMARY

Newborn screening provides an opportunity to identify and begin treatment early in individuals with CF. Whereas a single, optimal approach to screening does not exist, all programs can benefit from new findings regarding sweat testing, carrier detection, early pathophysiology, and clinical outcomes.