Newborn screening for cystic fibrosis

Research advances in molecular mechanisms underlying the pathogenesis of cystic fibrosis: From technical improvement to clinical applications (Review)

Cystic fibrosis (CF) is a chronic disease causing severe impairment to the respiratory system and digestive tracts. Currently, CF is incurable. As an autosomal recessive disorder, the morbidity of CF is significantly higher among Caucasians of European descent, whereas it is less pervasive among African and Asian populations. The disease is caused by identical mutations (homozygosity) or different mutations (heterozygosity) of an autosomal recessive mutation at position 7q31.2-q31.1 of chromosome 7. Diagnostic criteria and guidelines work concurrently with laboratory detection to facilitate precise CF detection. With technological advances, the understanding of CF pathogenesis has reached an unprecedented level, allowing for increasingly precise carrier screening, more effective early stage CF intervention and improved prognostic outcomes. These advances significantly increase the life quality and expectancy of patients with CF. Given the numerous improvements in the field of CF, the current review summarized the technical advances in the study of the molecular mechanisms underlying CF, as well as how these improvements facilitate the clinical outcomes of CF. Furthermore, challenges and obstacles to overcome are discussed.

Pathophysiology of cystic fibrosis and drugs used in associated digestive tract diseases

Cystic fibrosis (CF) causes chronic infections in the respiratory tract and alters the digestive tract. This paper reviews the most important aspects of drug treatment and changes in the digestive tract of patients with CF. This is a review of the literature, emphasizing the discoveries made within the last 15 years by analyzing scientific papers published in journals indexed in the Scientific Electronic Library Online, Sciences Information, United States National Library of Medicine and Medical Literature Analysis and Retrieval System Online databases, both in English and Portuguese, using the key words: cystic fibrosis, medication, therapeutic, absorption, digestion. Randomized, observational, experimental, and epidemiological clinical studies were selected, among others, with statistical significance of 5%. This review evaluates the changes found in the digestive tract of CF patients including pancreatic insufficiency, constipation and liver diseases. Changes in nutritional status are also described. Clinical treatment, nutritional supplementation and drug management were classified in this review as essential to the quality of life of CF patients, and became available through public policies for monitoring and treating CF. The information gathered on CF and a multi professional approach to the disease is essential in the treatment of these patients.

Diagnosis of cystic fibrosis

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene that results in abnormal viscous mucoid secretions in multiple organs and whose main clinical features are pancreatic insufficiency and chronic endobronchial infection. Although it was initially defined and diagnosed based on clinical features and sweat chloride measurement, an in vivo method of assessing CFTR function, the discovery of the CFTR gene in 1989 revealed a broad spectrum of CF phenotypes associated with specific CFTR gene mutations. In this article, we will review the indications for sweat testing, alternative techniques to diagnose CF, and the approach to patients with an ambiguous or indeterminate diagnosis of CF.

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.

Potential impact of newborn screening for cystic fibrosis on child survival: a systematic review and analysis

OBJECTIVE

To estimate the population impact of child mortality as a result of cystic fibrosis (CF) potentially preventable by newborn screening.

STUDY DESIGN

A systematic literature review of mortality in children with classic CF without meconium ileus (MI) in screened and unscreened cohorts was extended by contacting investigators for unpublished data. In addition, survival in US states with and without newborn screening (NBS) programs for CF was compared using data from the Cystic Fibrosis Foundation Patient Registry (CFFPR).

RESULTS

Among non-US studies, CF-related mortality risk to approximately 10 years of age was lower by 5 to 10 per 100 in screened cohorts. Unpublished US data from a trial of NBS for CF indicate no CF-related deaths to 10 years of age in either cohort. CFFPR data suggest improved survival among children with CF born in US states with NBS, with a CF-related mortality difference to 10 years of age between the screened and unscreened groups between 1.5 and 2 per 100 children with CF without MI.

CONCLUSION

In addition to improving nutritional outcomes, newborn screening for CF may result in improved child survival. The absolute differential in mortality risk, although modest in size, appears comparable to NBS for certain other genetic disorders.

Proteomic Analysis of Sputum from Adults and Children with Cystic Fibrosis and from Control Subjects

RATIONALE

Recurrent pulmonary exacerbations are associated with progressive lung disease in cystic fibrosis (CF). Current definitions of an exacerbation, although not precisely defined, include new/worsening symptoms, declining lung function, and/or changing radiologic appearance. Early diagnosis of exacerbations by rapid noninvasive means should expedite therapeutic intervention, thereby minimizing lung damage.

OBJECTIVES

To identify biomarkers of lung exacerbation for point-of-care monitoring of CF lung disease progression.

METHODS

Saline-induced sputum was collected from adults with CF with an exacerbation and requiring hospitalization (FEV(1) < 60%), a subset of these adults at hospital discharge, children with stable CF and preserved lung function (FEV(1) > 70%), and control subjects (FEV(1) > 80%). Sputum was arrayed by two-dimensional electrophoresis and differentially expressed proteins were identified by proteomic analysis.

MEASUREMENTS AND MAIN RESULTS

Sputum profiles from adults with CF with an exacerbation were characterized by extensive proteolytic degradation and influx of inflammation-related proteins, with some adults with CF approaching a "healthy" protein profile after hospitalization. Two children with CF showed profiles and biomarker expression resembling those of adults with an exacerbation. Levels of differentially expressed myeloperoxidase, cleaved alpha(1)-antitrypsin, IgG degradation, interleukin-8, and total protein concentration, together with their correlation to FEV(1), were statistically significant. Statistical correlation analyses indicated that changes in myeloperoxidase expression and IgG degradation were the strongest predictors of FEV(1).

CONCLUSIONS

We identified extensive protein degradation and differentially expressed proteins as biomarkers of inflammation relating to pulmonary exacerbations. Prediction of exacerbation onset and more precise evaluation of the extent of resolution with treatment could be achieved by including biomarkers in standard assessment.

Development of population-based newborn screening for severe combined immunodeficiency

BACKGROUND

Severe combined immunodeficiency (SCID) is a treatable, inherited lack of cellular and humoral immunity caused by diverse mutations in several different genes and leading to death in infancy unless immune reconstitution is provided. Currently no population screening exists for SCID, but early diagnosis would improve outcome.

OBJECTIVE

Because all patients with SCID make few or no T cells, we asked whether the absence of T-cell receptor excision circles (TRECs), DNA episomes in newly formed T cells, could identify SCID regardless of genotype.

METHODS

DNA isolated from dried blood spots was assayed by real-time PCR to quantitate TRECs. Control PCR was performed on a segment of the beta-actin gene. After pilot studies with adult and cord blood control subjects, blood from SCID patients was spotted onto filters and tested, followed by screening of actual blood spots from the Maryland Newborn Screening Program. Finally, newborn blood spots were recovered and tested from 2 infants after their diagnosis of SCID.

RESULTS

In contrast to filters from the newborn screening program, which had a mean of 1020 TRECs in two 3-mm punches, samples from 23 infants with SCID had <30 TRECs. The newborn screening filter was retrieved from a state laboratory for one of these infants plus another infant who had died of SCID previously; although both samples had detectable beta-actin DNA, neither had TRECs.

CONCLUSION

TRECs are a stable analyte that can identify T-cell lymphopenia in newborn dried blood spots so that infants with SCID can receive early, life-saving treatment.

Update on newborn screening for cystic fibrosis

PURPOSE OF REVIEW

Cystic fibrosis (CF) is the most common lethal genetic disorder in the United States to be identified in childhood. In November 2003 the US Cystic Fibrosis Foundation and the Centers for Disease Control and Prevention convened an expert panel to review the indications for CF newborn screening. In this review we discuss the information during the year leading up to this meeting as well as publications since the meeting.

RECENT FINDINGS

During the past several years an increasing number of CF patients have been diagnosed with newborn screening. These patients have demonstrated several benefits to screening while also uncovering new challenges. Health benefits have included improved nutrition persisting for many years and the avoidance of nutritional complications. Early identification has also meant that these often clinically healthy infants are being followed in CF centers for care. This has added to the need for avoiding infection risks to which these patients might not have otherwise been exposed. Psychosocial benefits include the avoidance of stress due to delayed diagnosis as well as assistance with family planning. Psychosocial challenges include carrier identification and detection of patients with mild disease or without a clear diagnosis.

SUMMARY

Although no study has definitively shown reduced lung disease or prolonged survival in CF patients detected by newborn screening, the general consensus is that improved nutrition and cognitive potential, in addition to the reduced costs for hospitalization and intensive therapies, support the benefits of screening.