Update on newborn screening for cystic fibrosis

The Changing Face of Cystic Fibrosis: An Update for Anesthesiologists

Cystic fibrosis (CF) is the most common fatal genetic disease in North America. While CF is more common among Whites, it is increasingly being recognized in other races and ethnicities. Although there is no cure, life expectancy has steadily improved, with the median survival exceeding 46 years in the United States. There are now more adults than children with CF in the United States. CF is caused by mutations in a gene that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) protein, expressed in many epithelial cells. More than 2100 CFTR mutations have been linked to CF, and newer CFTR modulator drugs are being used to improve the production, intracellular processing, and function of the defective CFTR protein. CF is a multisystem disease that affects primarily the lungs, pancreas, hepatobiliary system, and reproductive organs. Anesthesiologists routinely encounter CF patients for various surgical and medical procedures, depending on the age group. This review article focuses on the changing epidemiology of CF, advances in the classification of CFTR mutations, the latest innovations in CFTR modulator therapies, the impact of the coronavirus disease pandemic, and perioperative considerations that anesthesiologists must know while caring for patients with CF.

Measuring and improving respiratory outcomes in cystic fibrosis lung disease: opportunities and challenges to therapy

Cystic fibrosis (CF) is a life-shortening disease with significant morbidity. Despite overall improvements in survival, patients with CF experience frequent pulmonary exacerbations and declining lung function, which often accelerates during adolescence. New treatments target steps in the pathogenesis of lung disease, such as the basic defect in CF (CF Transmembrane Conductance Regulator [CFTR]), pulmonary infections, inflammation, and mucociliary clearance. These treatments offer hope but also present challenges to patients, clinicians, and researchers. Comprehensive assessment of efficacy is critical to identify potentially beneficial treatments. Lung function and pulmonary exacerbation are the most commonly used outcome measures in CF clinical research. Other outcome measures under investigation include measures of CFTR function; biomarkers of infection, inflammation, lung injury and repair; and patient-reported outcomes. Molecular diagnostics may help elucidate the complex CF airway microbiome. As new treatments are developed for patients with CF, efforts should be made to balance treatment burden with quality of life. This review highlights emerging treatments, obstacles to optimizing outcomes, and key future directions for research.

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.

Pediatricians' attitudes toward expanding newborn screening

OBJECTIVE

Traditional population screening focuses on conditions for which early treatment prevents severe morbidity and mortality. The classic example in pediatrics is newborn screening for phenylketonuria, which began in the 1960s. In 1968, Wilson and Jungner delineated 10 criteria that would justify population screening. These criteria have been reaffirmed by many newborn screening task forces as the standard for adding conditions to newborn screening programs. Today, however, some newborn screening programs are expanding to include conditions that may not meet all of the traditional screening criteria. Little is known about pediatricians' attitudes toward expanding screening. We examine the attitudes of pediatricians and pediatric subspecialists toward screening for cystic fibrosis (CF), Duchenne muscular dystrophy (DMD), fragile X, and type 1 diabetes.

METHODS

A cross-sectional survey was conducted of 600 pediatricians, including those who are members of the section of genetics, endocrinology, pulmonology, and neurology of the American Academy of Pediatrics. For each condition, pediatricians were queried about (1) testing high-risk infants, (2) newborn screening, and (3) population screening or testing beyond the newborn period. Demographic data were also collected.

RESULTS

A total of 232 (43%) of 537 eligible pediatricians returned surveys. More than 75% support testing high-risk infants for all conditions except type 1 diabetes. CF was the only condition for which >50% supported newborn screening. Newborn screening was preferred over screening older infants for all conditions except fragile X. Subspecialty affiliation did not have a significant impact with respect to attitudes about testing high-risk children, newborn screening, or screening beyond infancy. We analyzed the data by the number of patients with the queried condition under the physician's care and by the number of affected family members. Neither aspect was significant. We also analyzed the data by gender, by year of residency graduation, and by geographic location. None of these factors revealed significant differences in responses. For each condition, 8% to 41% of physicians would personally choose to test their own infant. We found that physicians' opinion about what they would want for their own children correlated with their attitude about population newborn screening. Those who would personally choose testing of their own infants were highly likely to support newborn screening for CF (98%), DMD (94%), and fragile X (98%), but only 78% of those who would personally opt for newborn screening of type 1 diabetes would also endorse population-based screening. This was statistically significant for each condition. Those who would choose not to test their own infants were significantly less likely to support newborn screening of the general population. One third of those who did not want to test their own newborns for CF supported population screening, whereas only one fifth supported DMD and fragile X population screening. For type 1 diabetes, 98% of those who would not personally choose newborn testing did not want it offered as a population screening program.

CONCLUSIONS

Most physicians support diagnostic genetic testing of high-risk children but are less supportive of expanding newborn screening, particularly for conditions that do not meet the Wilson and Jungner criteria. Willingness to expand newborn screening does not correlate with professional characteristics but rather with personal interest in testing of their own children.

Newborn screening and the pediatric practitioner

Since the beginning of newborn screening for metabolic and other disorders in 1964, advances in the understanding of the disorders identified and development of new methods of testing newborn screening blood spots have contributed to improved health in children. Pediatricians and others involved in the health care of infants must be able to participate in the assessment and confirmatory testing of infants who have an abnormal test result and in the care of infants identified with a disorder. Expansion in the technology and number of disorders identified has complicated this process. As more and a greater variety of disorders are tested for and identified, a crucial collaborative role has emerged for the newborn screening programs and their public health professionals, the tertiary care specialists in the disorders and the primary care clinicians who comprise the medical home of the infants identified. This collaboration needs to provide prompt results of the newborn screening tests, expeditious and expert confirmatory testing and an effective care plan for the affected infant to realize the benefits of treatment for children with otherwise devastating disorders.