Cystic fibrosis newborn screening: using experience to optimize the screening algorithm

Risk of CFTR-related disorders and cystic fibrosis in an Italian cohort of CRMS/CFSPID subjects in preschool and school age

The identification of cystic fibrosis screening-positive, inconclusive diagnosis (CFSPID) in infants is a controversial outcome of newborn screening for cystic fibrosis (CF). Today, despite improvements in the knowledge of CFSPID and the description of several cohorts, little data are available on cohorts with a follow-up period of more than 6 years. In this study, we report the outcomes of an Italian cohort of CFSPID individuals with CFSPID or formerly CFTR-related disorders (CFTR-RD) (CFSPID > CFTR-RD) or diagnosed with CF (CFSPID > CF). This was an observational and multicentre Italian study collecting clinical data on CFSPID born between the period January 1, 2011, and December 13, 2019. A total of 268 participants were included: 243 with persistent CFSPID, 7 with CFSPID > CFTR-RD, and 18 with CFSPID > CF. The trend of sweat chloride (SC) values, percentage of definitive diagnoses, lung function in school-aged children, and development of CF-related complications were evaluated. At the end of the observation period, almost 80% of the individuals with CFSPID did not have a conclusive diagnosis. A total of 29 children (10.8%) transitioned to a diagnosis of CF for pathological SC values (≥ 60 mmol/L) or multi-organ involvement, and 18 (6.7%) to CFTR-RD. Children who were followed up for > 6 years (median age, 7.5 years; range, 6.04-10.5) had normal lung function and were pancreatic sufficient, and the evolution in CF was only present in two cases.

CONCLUSION

Most Italian preschool and school-aged children with CFSPID did not have a conclusive diagnosis, and progression to CF was unlikely in children > 6 years of age. An annual follow-up could be indicated to identify early evolution in clinical features consistent with a CFTR-RD.

WHAT IS KNOWN

• Cystic Fibrosis newborn screening identifies also subjects with an inconclusive diagnosis (CFSPID). • Over time a variable percentage of CFSPIDs will be diagnosed as CF. • Little data is available on CFSPIDs with a follow-up period of more than six years.

WHAT IS NEW

• 80% of Italian preschool and school-age CFSPIDs not have a conclusive diagnosis. • Italian preschool and school-age CFSPIDs have normal lung function and are pancreatic sufficient. • Annual follow-up after 6 years is recommended in CFSPID with abnormal LCI2.5 or with a CF-causing variant in trans with a VVCC.

Early diagnosis from newborn screening maximises survival in severe cystic fibrosis

Newborn screening (NBS) for cystic fibrosis (CF) has been gradually established in several countries, but scant data are available on its long-term effects on survival. Our objective was to evaluate the long-term effects of CF NBS on survival. 586 patients, diagnosed and followed between 1971 and 2014 at the Verona CF Centre were analysed. Eligibility was confirmed in 342 cases diagnosed by NBS, 101 with meconium ileus and 143 through symptoms (44 out of 143 were NBS false negatives). The primary end-point was the 30-year overall survival in patients diagnosed by NBS. Patients were grouped according to the number of hospitalisations for respiratory or nutritional symptoms in the first 3 years of life: 0 (mild), 1-2 (moderate) and ≥3 (severe). Survival in NBS and symptoms groups was compared. The 30-year survival probability of the NBS group was 80.1% (95% CI 71.4-86.4%); in the symptoms group it was 71.0% (95% CI 62.2-78.2%). The 20-year survival was significantly higher in the NBS versus symptoms group in the severe (85% versus 64%, p=0.007) and moderate (94% versus 86%, p=0.016) groups. An adjusted Cox-model estimation confirmed differences in both the groups. Poor outcome associated with early severe presentation of CF is tempered by NBS.

Optimization of the French cystic fibrosis newborn screening programme by a centralized tracking process

Objectives To evaluate the French cystic fibrosis newborn screening algorithm, based on data tracked by a centralized monitoring process, from 2002 to 2014. The programme aimed to attain European Standards in terms of positive predictive value, sensitivity, the ratio of screen positive patients diagnosed with cystic fibrosis to infants who screen positive but with inconclusive diagnosis (CFSPID), and time to diagnosis. Methods Retrospective analysis of programme performance, compliance with the algorithm, and changes in screening strategy. Results Modifications in the flow chart protocol improved the positive predictive value to 0.31 while maintaining the sensitivity at 0.95. Among infants diagnosed with cystic fibrosis, or identified as CFSPID, sweat test results were obtained for 94%, and two mutations were identified after exhaustive screening for the gene, when applicable, in 99.6%. The rate of pending diagnosis was very low (0.5%). The ratio of infants with cystic fibrosis:CFSPID was 6.3:1. Age at initial visit at the CF centre was ≤ 35 days, respectively, in 53%/26%. Conclusion Performances were in agreement with European standards, but timeliness of initial visit needed improvement. Our data complement an accumulating body of evidence demonstrating that attention must be paid to such ethical considerations as limiting carrier detection and inconclusive diagnosis. Newborn screening programmes should have a rigorous centralized monitoring process to warrant adjustments for improving performance to attain consensus guidelines.

Utility of a very high IRT/No mutation referral category in cystic fibrosis newborn screening

Newborn screening for Cystic Fibrosis (CF) began in New York in October, 2002 using immunoreactive trypsinogen (IRT)/DNA methodology. Infants with at least one CFTR mutation or very high IRT and no mutations (VHIRT) are referred for sweat testing. In a preliminary analysis, we noted a very low positive predictive value (PPV) and preponderance of Hispanic infants in the group of infants with CF referred for VHIRT, which led to a decision to revise, but not eliminate, the VHIRT category. Automatic referral for specimens with VHIRT collected on the day of birth was eliminated, and the VHIRT threshold was raised from 0.2% to 0.1%. In this report, we describe outcomes from VHIRT referrals among 2.4 million infants screened between March 2003 and February 2013. Following the algorithm change, referrals decreased by 37.8% overall (annual mean 1,485 vs. 923), and the VHIRT PPV improved (0.6-1.0%). The number of infants diagnosed has remained consistent at 1 in 4,400 births. The proportion of Black/Hispanic/Asian/Other infants with confirmed CF, CFTR-related metabolic syndrome (CRMS), or possible CF/CRMS was 21.3% in infants with 1-2 mutations, but 75.8% in the VHIRT group. In conclusion, although the PPV among VHIRT referrals remains low, had this category never been implemented, 24 infants with confirmed CF, and 9 infants with CRMS or possible CF/CRMS, most of whom were Hispanic, would have been missed over the 10 years. Information from this study may be helpful in assessing the need for the VHIRT category and algorithm changes in other screening programs.

Improved screening for cystic fibrosis-related diabetes by an integrated care team using an algorithm

OBJECTIVE

To determine whether implementation of a standardized, clinic-based algorithm improves compliance with cystic fibrosis-related diabetes (CFRD) screening guidelines.

STUDY DESIGN

A CFRD screening algorithm was developed as part of a quality improvement initiative through collaboration between the pediatric pulmonary and endocrine divisions and implemented prospectively to children aged 8-17 years in our CF center for a 6-month period. The primary outcome measure was the percentage rate of CF patients who were appropriately screened with an oral glucose tolerance test (OGTT) during the quality improvement period as compared to the year prior.

RESULTS

Ninety-seven percent (37/38) of OGTTs were appropriately ordered by providers, and 89% (34/38) of patients obtained the OGTT at the completion of the quality improvement period. Compared with the percentage of eligible patients completing the OGTT the year prior, the use of the algorithm significantly improved screening (P = 0.03). Data collected 1-year post-algorithm implementation revealed 97% (33/34) of OGTTs were ordered and 79% (27/34) of OGTTs were completed. The use of the algorithm 1-year post-implementation did not reveal a significant improvement in screening when compared to the reference year and implementation period (P = 0.08).

CONCLUSIONS

Implementation of a clinical algorithm resulted in a statistically significant improvement in screening during the quality improvement period, but this improvement was not sustained the following year despite continued physician compliance with ordering the OGTT. Barriers to patient compliance need to be explored.

Expanded newborn screening and confirmatory follow-up testing for inborn errors of metabolism detected by tandem mass spectrometry

Newborn screening (NBS) of inborn errors of metabolism (IEM) is a coordinated comprehensive system consisting of education, screening, follow-up of abnormal test results, confirmatory testing, diagnosis, treatment, and evaluation of periodic outcome and efficiency. The ultimate goal of NBS and follow-up programs is to reduce morbidity and mortality from the disorders. Over the past decade, tandem mass spectrometry (MS/MS) has become a key technology in the field of NBS. It has replaced classic screening techniques of one-analysis, one-metabolite, one-disease with one analysis, many-metabolites, and many-diseases. The development of electrospray ionization (ESI), automation of sample handling and data manipulation have allowed the introduction of expanded NBS for the identification of numerous conditions on a single sample and new conditions to be added to the list of disorders being screened for using MS/MS. In the case of a screened positive result, a follow-up analytical test should be performed for confirmation of the primary result. The most common confirmatory follow-up tests are amino acids and acylcarnitine analysis in plasma and organic acid analysis in urine. NBS should be integrated with follow-up and clinical management. Recent improvements in therapy have caused some disorders to be considered as potential candidates for NBS. This review covers some of the basic theory of expanded MS/MS and follow-up confirmatory tests applied for NBS of IEM.

Newborn screening for cystic fibrosis: Polish 4 years' experience with CFTR sequencing strategy

Newborn screening for cystic fibrosis (NBS CF) in Poland was started in September 2006. Summary from 4 years' experience is presented in this study. The immunoreactive trypsin/DNA sequencing strategy was implemented. The group of 1,212,487 newborns were screened for cystic fibrosis during the programme. We identified a total of 221 CF cases during this period, including, 4 CF cases were reported to be omitted by NBS CF. Disease incidence in Poland based on the programme results was estimated as 1/4394 and carrier frequency as 1/33. The frequency of the F508del was similar (62%) to population data previously reported. This strategy allowed us to identify 29 affected infants with rare genotypes. The frequency of some mutations (eg, 2184insA, K710X) was assessed in Poland for the first time. Thus, sequencing assay seems to be accurate method for screening programme using blood spots in the Polish population.

β-adrenergic sweat secretion as a diagnostic test for cystic fibrosis

RATIONALE

β-Adrenergically induced sweat secretion offers an expedient method to assess native cystic fibrosis transmembrane conductance regulator (CFTR) secretory function in vivo.

OBJECTIVES

To evaluate the sensitivity, specificity, and reliability of a test based on the activity and secretory function of CFTR in the sweat gland.

METHODS

Primary and validation trials with prospectively ascertained healthy control subjects, obligate heterozygotes, and patients with a CFTR-related disorder and CF (pancreatic sufficient and insufficient).

MEASUREMENTS AND MAIN RESULTS

Diagnostic accuracy and reliability of β-adrenergic sweat secretory rates using an evaporimeter was assessed and compared with sweat chloride concentrations. The cholinergically stimulated mean sweat rate did not differ among groups. The mean maximal β-adrenergically stimulated sweat rate in heterozygotes was about half the rate of healthy control subjects, and completely absent in pancreatic-insufficient patients with CF and pancreatic-sufficient patients with CF (P < 0.0001). Subjects with a CFTR-related disorder showed reduced or absent β-adrenergic sweat secretion. The β-adrenergic secretory response demonstrated high diagnostic accuracy (area under a characteristic receiver-operator curve = 0.99; 95% confidence interval, 0.97-1.00) and reliability (intraclass correlation, 0.90; 95% confidence interval, 0.81-0.95). The diagnostic cutoff level for CF, derived from the primary trial, correctly identified all control subjects, heterozygotes, and patients with CF in the validation cohort, whereas concurrent sweat chloride measurements misclassified one heterozygote and five subjects with CF. The cholinergic and β-adrenergic sweat secretion rates were lower in women compared with men (P < 0.001).

CONCLUSIONS

β-Adrenergic sweat secretion rate determined by evaporimetry is an accurate and reliable technique to assess different levels of CFTR function and to identify patients with CF.

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.

A re-examination of the use of ethnicity in prenatal carrier testing

In April 2011, the American Congress of Obstetricians and Gynecologists (formerly the American College of Obstetrics and Gynecology [ACOG]), updated its policy on carrier screening for cystic fibrosis and proposed that because of the increasing difficulty in assigning a single ethnicity to individuals, "It is reasonable, therefore to offer CF carrier screening to all patients." However, ACOG continues to use ethnicity in its guidelines about carrier testing for autosomal recessive disorders like sickle cell disease (SCD) and Tay-Sachs disease (TSD). This practice is in marked contrast with newborn screening (NBS) which is universally provided for all conditions. In this manuscript, I evaluate the discrepant role of ethnicity in NBS and carrier screening. I argue that ACOG needs to adopt the position it now takes for CF regarding prenatal carrier testing for all conditions. To promote equity in prenatal testing decision making, health care policies must acknowledge the diversity of the populations that we serve and empower all women and couples to make more fully informed reproductive decisions by offering prenatal carrier testing to all.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

CONCLUSION

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