Nongenetic influences on cystic fibrosis outcomes

Social-environmental phenotypes of rapid cystic fibrosis lung disease progression in adolescents and young adults living in the United States

Background

Cystic fibrosis (CF) is a genetic disease but is greatly impacted by non-genetic (social/environmental and stochastic) influences. Some people with CF experience rapid decline, a precipitous drop in lung function relative to patient- and/or center-level norms. Those who experience rapid decline in early adulthood, compared to adolescence, typically exhibit less severe clinical disease but greater loss of lung function. The extent to which timing and degree of rapid decline are informed by social and environmental determinants of health (geomarkers) is unknown.

Methods

A longitudinal cohort study was performed (24,228 patients, aged 6-21 years) using the U.S. CF Foundation Patient Registry. Geomarkers at the ZIP Code Tabulation Area level measured air pollution/respiratory hazards, greenspace, crime, and socioeconomic deprivation. A composite score quantifying social-environmental adversity was created and used in covariate-adjusted functional principal component analysis, which was applied to cluster longitudinal lung function trajectories.

Results

Social-environmental phenotyping yielded three primary phenotypes that corresponded to early, middle, and late timing of peak decline in lung function over age. Geographic differences were related to distinct cultural and socioeconomic regions. Extent of peak decline, estimated as forced expiratory volume in 1 s of % predicted/year, ranged from 2.8 to 4.1 % predicted/year depending on social-environmental adversity. Middle decliners with increased social-environmental adversity experienced rapid decline 14.2 months earlier than their counterparts with lower social-environmental adversity, while timing was similar within other phenotypes. Early and middle decliners experienced mortality peaks during early adolescence and adulthood, respectively.

Conclusion

While early decliners had the most severe CF lung disease, middle and late decliners lost more lung function. Higher social-environmental adversity associated with increased risk of rapid decline and mortality during young adulthood among middle decliners. This sub-phenotype may benefit from enhanced lung-function monitoring and personalized secondary environmental health interventions to mitigate chemical and non-chemical stressors.

Aiming to Improve Equity in Pulmonary Health: Cystic Fibrosis

This review summarizes the evidence of health disparities in cystic fibrosis (CF), an autosomal recessive genetic disorder with substantial variation in disease progression and outcomes. We review disparities by race, ethnicity, socioeconomic status, geographic location, gender identity, or sexual orientation documented in the literature. We outline the mechanisms that generate and perpetuate such disparities across levels and domains of influence and assess the implications of this evidence. We then recommend strategies for improving equity in CF outcomes, drawing on recommendations for the general population and considering approaches specific to people living with CF.

Cystic Fibrosis Screen Positive, Inconclusive Diagnosis Genotypes in People with Cystic Fibrosis from the U.S. Patient Registry

Rationale: Variants within the cystic fibrosis (CF) transmembrane conductance regulator gene, CFTR, that are of unknown significance or are categorized as non-CF causing may be observed in persons with CF. These variants are frequently detected in children with inconclusive newborn screen results and, in some cases, may be associated with a benign presentation in early childhood that progresses to a CF phenotype later in life. Objectives: To analyze data from individuals enrolled in the U.S. Cystic Fibrosis Foundation Patient Registry who have received a diagnosis of CF and who have variants found in a population of children with a CF screen positive, inconclusive diagnosis (CFSPID). Methods: This retrospective review analyzed registry data from individuals with a diagnosis of CF who also harbor one or more variants of interest because of their frequency within a CFSPID population and/or their interpretation as non-CF causing. Three groups were defined by the number of CF-causing variants identified (CF-Cx2, CF-Cx1, and CF-Cx0), which were reported in addition to the variant(s) of interest. Multivariate quantile regression modeling of the outcome for forced expiratory volume in 1 second (FEV1) generated a disease severity score for each person determined by six selected variables. Median scores were calculated for the three groups. Results: Patients carrying one CF-causing variant and at least one variant of interest (CF-Cx1) had higher median disease severity scores compared with those carrying CF-Cx2, suggesting a milder phenotype (P < 0.05). However, there was no statistically significant difference in scores between CF-Cx2 and the two other groups combined (CF-Cx1 and CF-Cx0; P = 0.33). Analysis revealed that the CF-Cx1 and CF-Cx0 groups, when compared with the CF-Cx2 group, had later median diagnoses (8 years vs. newborn; P < 0.0001), lower median sweat chloride (48 mmol/L vs. 94.5 mmol/L; P < 0.0001), lower prevalence of pancreatic insufficiency (29% vs. 78%; P < 0.0001), and higher median FEV1% predicted (95% vs. 87%; P = 0.0002). Conclusions: Individuals with CF who have specific variants frequently identified in children with CFSPID have a similar range of disease severity scores compared with those who have two CF-causing variants, but a milder phenotype overall. Variants that should be given careful scrutiny because of their high prevalence are G576A+R668C, T854T, R75Q, F1052V, R1070W, R31C, and L967S.

Socioeconomic determinants of respiratory health in patients with cystic fibrosis: implications for treatment strategies

INTRODUCTION

Great variation exists in the progression and outcomes of cystic fibrosis (CF) lung disease, due to both genetic and environmental influences. Social determinants mediate environmental exposures and treatment success; people with CF from socioeconomically disadvantaged backgrounds have worse health and die younger than those in more advantaged positions.

AREAS COVERED

This paper reviews the literature on the mechanisms that are responsible for generating and sustaining disparities in CF health, and the ways by which social determinants translate into health advantages or disadvantages in people with CF. The authors make recommendations for addressing social risk factors in CF clinical practice.

EXPERT OPINION

Socioeconomic factors are not dichotomous and their impact is felt at every step of the social ladder. CF care programs need to adopt a systematic protocol to screen for health-related social risk factors, and then connect patients to available resources to meet individual needs. Considerations such as daycare, schooling options, living and working conditions, and opportunities for physical exercise and recreation as well as promotion of self-efficacy are often overlooked. In addition, advocacy for changes in public policies on health insurance, environmental regulations, social welfare, and education would all help address the root causes of CF health inequities.

Cystic fibrosis lung transplant recipients 10 years of age or younger: Predisposing factors for end-stage disease

BACKGROUND

The largest age group among children and adolescents referred for lung transplantation for cystic fibrosis (CF) have been those in the pubertal or postpubertal age range. However, over 100 younger patients with CF have undergone lung transplantation over the last three decades in the United States.

METHODS

We performed a retrospective review of our experience with 18 children with CF who underwent lung transplantation in our center before the age of 11 years and compared them to our older CF lung transplant recipients and our larger CF Center population.

RESULTS

The transplant population was demographically distinct from our CF center in terms of ethnicity, country of origin, and insurance status. Other notable findings were a high prevalence of methicillin-resistant Staphylococcus aureus, a high prevalence of CF-related diabetes mellitus, and a high prevalence of consolidated lobar or whole lung disease. Posttransplant outcomes were comparable to those older than 10 years of age in our center until 5 years after transplant after which the younger cohort showed a superior enduring survival.

CONCLUSIONS

In an era of increasingly effective medications modifying the natural history of CF, identification of risk factors for early severe lung disease in CF remains relevant to permit interventions to prevent or postpone the time of future lung transplantation.

CFTR bearing variant p.Phe312del exhibits function inconsistent with phenotype and negligible response to ivacaftor

The chloride channel dysfunction caused by deleterious cystic fibrosis transmembrane conductance regulator (CFTR) variants generally correlates with severity of cystic fibrosis (CF). However, 3 adults bearing the common severe variant p.Phe508del (legacy: F508del) and a deletion variant in an ivacaftor binding region of CFTR (p.Phe312del; legacy: F312del) manifested only elevated sweat chloride concentration (sw[Cl-]; 87-105 mEq/L). A database review of 25 individuals with F312del and a CF-causing variant revealed elevated sw[Cl-] (75-123 mEq/L) and variable CF features. F312del occurs at a higher-than-expected frequency in the general population, confirming that individuals with F312del and a CF-causing variant do not consistently develop overt CF features. In primary nasal cells, CFTR bearing F312del and F508del generated substantial chloride transport (66.0% ± 4.5% of WT-CFTR) but did not respond to ivacaftor. Single-channel analysis demonstrated that F312del did not affect current flow through CFTR, minimally altered gating, and ablated the ivacaftor response. When expressed stably in CF bronchial epithelial (CFBE41o-) cells, F312del-CFTR demonstrated residual function (50.9% ± 3.3% WT-CFTR) and a subtle decrease in forskolin response compared with WT-CFTR. F312del provides an exception to the established correlation between CFTR chloride transport and CF phenotype and informs our molecular understanding of ivacaftor response.

Changes in Care during the COVID-19 Pandemic for People with Cystic Fibrosis

Rationale

Cystic fibrosis (CF) centers transitioned to telemedicine during the spring 2020 peak of the coronavirus disease (COVID-19) pandemic.

Objectives

We hypothesized that people with CF (pwCF) with more severe disease would be more likely to be seen in-person.

Methods

We used paired t tests to compare within-subject changes in body mass index (BMI) and percentage predicted forced expiratory volume in one second (FEV₁) and calculated relative risk (RR) to compare pulmonary exacerbations (PEx) between pwCF enrolled in the CF Foundation Patient Registry with at least one in-person clinic visit after March 15 in both 2019 and 2020.

Results

Overall, the proportion of clinical encounters that were in-person clinic visits decreased from 91% in 2019 to a low of 9% in April 2020. Among pwCF seen after March 15 in both 2019 and 2020, the mean (95% confidence interval [CI]) FEV₁ percentage predicted was 1.3% (0.1–2.4) predicted higher in 2020 for children 6 to <12 years of age, and 7.5% (7.1–7.9) predicted higher in 2020 among pwCF ⩾12 years of age eligible for the highly effective CF transmembrane conductance regulator modulator, elexacaftor-tezacaftor-ivacaftor (ETI). There was no difference in FEV₁ percentage predicted for pwCF ⩾12 years of age who were not eligible for ETI. Similarly, the mean (95% CI) BMI was 2.4 (2.0–2.8) percentile higher in 2020 for children 6 to <12 years of age and 5.2 (4.8–5.7) percentile higher in 2020 among children 12 to <18 years of age eligible for ETI. Mean (95% CI) BMI was 1.2 (1.2–1.3) (kg/m²) higher for pwCF ⩾18 years of age eligible for ETI, and 0.2 (0.1–0.3) (kg/m²) higher for pwCF ⩾18 years of age not eligible for ETI. The proportion of in-person clinic visits where any PEx was present was lower in 2020 compared with 2019, 25% compared with 38%, RR 0.82 (0.79–0.86).

Conclusions

The care of pwCF was substantially changed during the spring 2020 peak of the COVID-19 pandemic. Among pwCF seen in-person in both 2019 and 2020 after the spring peak of the COVID-19 pandemic, lung function and BMI were higher in 2020 for children 6 to <12 years of age and pwCF eligible for ETI.

Longitudinal changes and regional variation of incident infection rates at cystic fibrosis centers, United States 2010-2016

BACKGROUND

Multiple factors affect incident infection rates (IIR) for Pseudomonas aeruginosa (PA) and methicillin resistant Staphylococcus aureus (MRSA) at CF care centers. We assessed changes in IIR across CF centers temporally associated with the 2013 Infection/Prevention & Control guidelines controlling for center-specific factors.

METHODS

Using the CF Foundation Patient Registry we defined and measured changes in IIR between 2010-2012 and 2014-2016. Data were compared to non-CF rates of MRSA and resistant PA in geographically similar regions. Characteristics of each CF center (n centers: Adult 54 in 2010 to 82 in 2016. Pediatric ∼106) and their respective population were evaluated for associations with IIR and with changes in IIR between the study periods.

RESULTS

Across the years 35613 patients were included. Incident-infection rates for PA (mean 19.2±0.04% Pediatric, 21.2±0.07% Adult centers) were higher than for MRSA (mean 9.4±0.03% Pediatric, 7.8±0.03% Adult). The IIR decreased for MRSA (-1.54±0.54%, p<0.001) and PA (-4.77±0.63%, p<0.001) at Pediatric but only for PA (-3.20±1.31, p=0.02) at Adult centers. Except for Adult CF, MRSA rates (CF and non-CF) were highest in the South. In 2014-2016, private insurance and a higher proportion of LatinX patients at a center were associated with lower MRSA IIR while larger center size, higher proportion of LatinX, and lower mean center-wide lung function were associated with higher PA IIR. Higher IIR in 2010-2012, were predictive of a more pronounced decrease in IIR in 2014-2016 for MRSA and PA (p<0.001). Different factors indicative of lower social status (smoking, insurance, education) in 2010-2012 predicted decreases in MRSA or PA IIR.

CONCLUSION

Comparisons of IIR across U.S. CF centers should consider location, ethnic background and socio-economic variables of a center's population.

Variation in treatment preferences of pulmonary exacerbations among Australian and New Zealand cystic fibrosis physicians

BACKGROUND

Despite advances in cystic fibrosis (CF) management and survival, the optimal treatment of pulmonary exacerbations remains unclear. Understanding the variability in treatment approaches among physicians might help prioritise clinical uncertainties to address through clinical trials.

METHODS

Physicians from Australia and New Zealand who care for people with CF were invited to participate in a web survey of treatment preferences for CF pulmonary exacerbations. Six typical clinical scenarios were presented; three to paediatric and another three to adult physicians. For each scenario, physicians were asked to choose treatment options and provide reasons for their choices.

RESULTS

Forty-nine CF physicians (31 paediatric and 18 adult medicine) participated; more than half reported 10+ years of experience. There was considerable variation in primary antibiotic selection; none was preferred by more than half of respondents in any scenario. For secondary antibiotic therapy, respondents consistently preferred intravenous tobramycin and a third antibiotic was rarely prescribed, except in one scenario describing an adult patient. Hypertonic saline nebulisation and twice daily chest physiotherapy was preferred in most scenarios while dornase alfa use was more variable. Most CF physicians (>80%) preferred to change therapy if there was no early response. Professional opinion was the most common reason for antibiotic choice.

CONCLUSIONS

Variation exists among CF physicians in their preferred choice of primary antibiotic and use of dornase alfa. These preferences are driven by professional opinion, possibly reflecting a lack of evidence to base policy recommendations. Evidence from high-quality clinical trials is needed to inform physician decision making.

Lung transplant referrals for individuals with cystic fibrosis: A pediatric perspective on the cystic fibrosis foundation consensus guidelines

Lung transplant referral guidelines for individuals with cystic fibrosis (CF) were published recently. Most of the recommendations focus on the specific indications and barriers to transplantation in adults with CF. Although the number of children with CF and end-stage lung disease continues to decrease, the specific issues related to pediatric patients merit further elucidation. We address each recommendation from the recent publication with a pediatric perspective. Furthermore, we note some significant differences between the practice and policy related to lung transplantation between Canada and the United States.

Mental health history and social barriers impacting caregivers of infants with cystic fibrosis

OBJECTIVES

Caregivers of infants with cystic fibrosis (CF) carry a heavy treatment burden for their child along with the inherent difficulties of raising an infant. This study investigated the impact of self-reported caregiver mental health diagnoses and social barriers during the 1st year of life on clinical outcomes.

METHODS

A retrospective chart review was conducted for infants seen in a large tertiary hospital CF clinic over a 5-year period. Baseline characteristics were collected, and documentation from physician and social work notes were reviewed. Demographics and clinical characteristics were compared by the presence or absence of self-reported mental health diagnoses, social barriers, and "emotional concern."

RESULTS

Analyses were conducted on 71 patients. Thirty-five percent of caregivers disclosed mental health diagnoses, 52% identified social barriers to care, and 55% reported feeling upset or fatigued. Having a caregiver with a self-reported mental health diagnosis was associated with tobacco smoke exposure (p < .001) and increased odds of hospitalizations (odds ratio [OR], 3.01; 95% confidence interval [CI], 1.49-6.06), emergency department/urgent care visits (OR, 3.17; 95% CI, 1.32-7.64), and longer lengths of stay (OR, 1.93; 95% CI, 1.69-2.20). Caregivers who expressed emotional concern had infants with significantly lower weight-for-length percentiles (p = .012).

DISCUSSION

Caregiver mental health and social barriers to care are important determinants to address as they may impact clinical outcomes in infants with CF. Identifying barriers and struggles early increases the likelihood that clinical teams can intervene and provide support. Further research into mental health and socioeconomic barriers faced by caregivers of infants with CF is crucial.

The role of inflammation in cystic fibrosis pulmonary exacerbations

INTRODUCTION

Cystic Fibrosis pulmonary exacerbations are critical events in the lives of people with CF that have deleterious effects on lung function, quality of life, and life expectancy. There are significant unmet needs in the management of exacerbations. We review here the associated inflammatory changes that underlie these events and are of interest for the development of biomarkers of exacerbation.

AREAS COVERED

Inflammatory responses in CF are abnormal and contribute to a sustained proinflammatory lung microenvironment, abundant in proinflammatory mediators and deficient in counter-regulatory mediators that terminate and resolve inflammation. There is increasing interest in these inflammatory pathways to discover novel biomarkers for pulmonary exacerbation management. In this review, we explore the inflammatory changes occurring during intravenous antibiotic therapy for exacerbation and how they may be applied as biomarkers to guide exacerbation therapy. A literature search was conducted using the PubMed database in February 2020.

EXPERT OPINION

Heterogeneity in inflammatory responses to treatment of a pulmonary exacerbation, a disease process with complex pathophysiology, limits the clinical utility of individual biomarkers. Biomarker panels may be a more successful strategy to capture informative changes within the CF population to improve pulmonary exacerbation management and outcomes.

Tobacco smoke exposure and socioeconomic factors are independent predictors of pulmonary decline in pediatric cystic fibrosis

BACKGROUND

Pulmonary decline in CF is heterogeneous, with socio-environmental factors contributing to this variability. Few studies have attempted to disentangle the effects of tobacco smoke exposure and socioeconomic factors on lung function deterioration in pediatric CF. The current study evaluates their contributions longitudinally across the entire U.S. CF care network population.

METHODS

Data from the CF Foundation Patient Registry were obtained on all individuals who at the end of 2016 were 6-18 years old. Lung function measures (ppFEV₁) for each person were calculated at each attained age. Multivariable analyses used mixed modeling to assess the impact of smoke exposure and socioeconomic factors on initial lung function and change over time.

RESULTS

The sample included 10,895 individuals contributing 65,581 person years. At age 6, ppFEV₁ of smoke-exposed children was 4.7% lower than among unexposed. The deficit persisted through age 18. In adjusted mixed models, smoke exposure and socioeconomic factors had independent, additive associations with lung function. Median ppFEV₁ declined 2.4% with smoke exposure, 4.9% with lower paternal education, 0.3% with public insurance, and increased 0.2% with each $10,000 annual household income. The effect of smoke exposure on ppFEV₁ was larger in disadvantaged children compared to privileged counterparts (3.2% vs 1.2%).

CONCLUSIONS

Smoke exposure and socioeconomic factors are independent risk factors for decreased ppFEV₁ in pediatric CF. Smoking cessation strategies should be emphasized at the time of CF diagnosis and reiterated during infancy and early childhood. Interventions may be prioritized in disadvantaged families, where the exposure has a disproportionately large effect.

Regional variations in longitudinal pulmonary function: A comparison of Hispanic and non-Hispanic subjects with cystic fibrosis in the United States

BACKGROUND

Hispanic subjects with cystic fibrosis (CF) have increased morbidity and mortality than non-Hispanic white subjects. The ethnic disparity in mortality varies by region. Factors influencing pulmonary function vary by both ethnicity and region.

OBJECTIVE

To determine if the ethnic difference in pulmonary function varies by region.

METHODS

This retrospective cohort study compared differences in longitudinal pulmonary function (percent-predicted forced vital capacity [FVC], forced expiratory volume in 1 second [FEV₁ ], forced expiratory flow at 25% to 75% [FEF_25-75 ], FEV₁ /FVC, and FEV₁ decline) between Hispanic and non-Hispanic white subjects with CF by Census region of the United States (West, South, Midwest, and Northeast). Subjects were of ages 6 to 25 years and in the CF Foundation Patient Registry from 2008 to 2013. We used linear mixed effects models with subject-specific slopes and intercepts, adjusting for 14 demographic and clinical variables.

RESULTS

Of 14 932 subjects, 1433 (9.6%) were Hispanic and 13 499 (90.4%) were non-Hispanic white. Hispanic subjects' FEV₁ was 9.0% (8.3%-9.8%) lower than non-Hispanic white subjects in the West, while Hispanic subjects' FEV₁ was only 4.0% (3.0%-5.0%) lower in the Midwest, 4.4% (3.1%-5.7%) lower in the Northeast, and 4.4% (3.2%-5.5%) lower in the South. Similarly, FVC and FEF_25-75 were lower among Hispanic subjects compared to non-Hispanic white subjects in all US regions, with the biggest differences in the West. Only in the West was FEV₁ /FVC significantly lower in Hispanic subjects (-0.019; -0.022 to -0.015). FEV₁ decline was not significantly different between ethnicities in any region.

CONCLUSIONS

In CF, Hispanic subjects have lower pulmonary function than non-Hispanic white subjects in all geographic regions with the largest difference in occurring in the West.

Environmental exposures during pregnancy: Mechanistic effects on immunity

In human studies, it is well established that exposures during embryonic and fetal development periods can influence immune health. Coupled with genetic predisposition, these exposures can alter lifetime chronic and infectious disease trajectory, and, ultimately, life expectancy. Fortunately, as research advances, mechanisms governing long-term effects of prenatal exposures are coming to light and providing the opportunity for intervention and risk reduction. For instance, human association studies have provided a foundation for the association of prenatal exposure to particulate matter with early immunosuppression and later allergic disease in the offspring. Only recently, the mechanisms mediating this response have been revealed and there is much we have yet to discover. Although cellular immune response is understood for many exposure scenarios, molecular pathways are still unidentified. This review will provide commentary and synthesis of the current literature regarding environmental exposures during pregnancy and mechanisms determining immune outcomes. Shared mechanistic features and current gaps in the state of the science are identified and discussed. To such purpose, we address exposures by their immune effect type: immunosuppression, autoimmunity, inflammation and tissue damage, hypersensitivity, and general immunomodulation.

Clinical expression of cystic fibrosis in a large cohort of Italian siblings

Background

A clinical heterogeneity was reported in patients with Cystic Fibrosis (CF) with the same CFTR genotype and between siblings with CF.

Methods

We investigated all clinical aspects in a cohort of 101 pairs of siblings with CF (including 6 triplets) followed since diagnosis.

Results

Severe lung disease had a 22.2% concordance in sib-pairs, occurred early and the FEV₁% at 12 years was predictive of the severity of lung disease in the adulthood. Similarly, CF liver disease occurred early (median: 15 years) and showed a concordance of 27.8% in sib-pairs suggesting a scarce contribution of genetic factors; in fact, only 2/15 patients with liver disease in discordant sib-pairs had a deficiency of alpha-1-antitrypsin (a known modifier gene of CF liver phenotype). CF related diabetes was found in 22 pairs (in 6 in both the siblings). It occurred later (median: 32.5 years) and is strongly associated with liver disease. Colonization by P. aeruginosa and nasal polyposis that required surgery had a concordance > 50% in sib-pairs and were poorly correlated to other clinical parameters. The pancreatic status was highly concordant in pairs of siblings (i.e., 95.1%) but a different pancreatic status was observed in patients with the same CFTR mutations. This suggests a close relationship of the pancreatic status with the “whole” CFTR genotype, including mutations in regulatory regions that may modulate the levels of CFTR expression. Finally, a severe course of CF was evident in a number of patients with pancreatic sufficiency.

Conclusions

Physicians involved in care of patients with CF and in genetic counseling must be aware of the clinical heterogeneity of CF even in sib-pairs that, at the state of the art, is difficult to explain.

Electronic supplementary material

The online version of this article (10.1186/s12890-018-0766-6) contains supplementary material, which is available to authorized users.

Transition to adulthood and adult health care for patients with sickle cell disease or cystic fibrosis: Current practices and research priorities

INTRODUCTION

A growing population of adults living with severe, chronic childhood-onset health conditions has created a need for specialized health care delivered by providers who have expertise both in adult medicine and in those conditions. Optimal care of these patients requires systematic approaches to healthcare transition (HCT). Guidelines for HCT exist, but gaps in care occur, and there are limited data on outcomes of HCT processes.

METHODS

The Single Disease Workgroup of the Lifespan Domain Task Force of the National Center for Advancing Translational Sciences Clinical and Translational Science Award programs convened a group to review the current state of HCT and to identify gaps in research and practice. Using cystic fibrosis and sickle cell disease as models, key themes were developed. A literature search identified general and disease-specific articles. We summarized key findings.

RESULTS

We identified literature characterizing patient, parent and healthcare provider perspectives, recommendations for transition care, and barriers to effective transition.

CONCLUSIONS

With increased survival of patients with severe childhood onset diseases, ongoing study of effective transition practices is essential as survival increases for severe childhood onset diseases. We propose pragmatic methods to enhance transition research to improve health and key outcomes.

Cystic Fibrosis Disease Modifiers: Complex Genetics Defines the Phenotypic Diversity in a Monogenic Disease

In many respects, genetic studies in cystic fibrosis (CF) serve as a paradigm for a human Mendelian genetic success story. From recognition of the condition as a heritable pathological entity to implementation of personalized treatments based on genetic findings, this multistep pathway of progress has focused on the genetic underpinnings of CF clinical disease. Along this path was the recognition that not all CFTR gene mutations produce the same disease and the recognition of the complex, multifactorial nature of CF genotype–phenotype relationships. The non- CFTR genetic components (gene modifiers) that contribute to variation in phenotype are the focus of this review. A multifaceted approach involving candidate gene studies, genome-wide association studies, and gene expression studies has revealed significant gene modifiers for multiple CF phenotypes. The bold challenges for the future are to integrate the findings into our understanding of CF pathogenesis and to use the knowledge to develop novel therapies.

What keeps children with cystic fibrosis awake at night?

BACKGROUND

Sleep disturbance is common in children with cystic fibrosis (CF) however there are limited studies investigating the causes for poor sleep quality. In a cross sectional observational study we aimed to evaluate the clinical correlates of sleep disturbance in this population.

METHODS

Children with CF (7-18years) free from pulmonary exacerbation completed medical review, overnight oximetry, the OSA-18 and 14days of actigraphy recordings with a sleep diary.

RESULTS

In addition to FEV₁ <80% and low baseline SpO₂, CF-related diabetes, PEG feeding and co-morbid behaviour disorder were associated with lower objective sleep quantity. Paternal smoking and a family member with a mood disorder were also associated with sleep disturbance. The use of electronic devices before bedtime was associated with lower sleep quantity and quality. FEV₁, nocturnal cough, age and a behaviour disorder predicted sleep duration. FEV₁, nocturnal cough, SpO₂ nadir and asthma predicted sleep efficiency. Conversely, sleep efficiency independently predicted FEV₁.

CONCLUSIONS

Reduced sleep quality in children with CF is related to lung health and co-morbidities. However, family characteristics and poor sleep hygiene in the child were also associated with sleep disturbance. Optimal management of CF would seem to be the primary intervention to alleviate children's sleep disturbance, however our data raises additional targets for attempts to improve sleep.

Socioeconomic Status, Smoke Exposure, and Health Outcomes in Young Children With Cystic Fibrosis

BACKGROUND

Lower socioeconomic status (SES) and environmental tobacco smoke (ETS) exposure are both associated with poorer disease outcomes in cystic fibrosis (CF), and children with low SES are disproportionately exposed to ETS. We analyzed a large cohort of young children with CF to distinguish the impact of SES and ETS on clinical outcomes.

METHODS

The Early Pseudomonas Infection Control Observational study enrolled Pseudomonas-negative young children with CF <13 years of age. An enrollment survey assessed SES and ETS exposures. Forced expiratory volume in 1 second (FEV₁), crackles and wheezes, and weight-for-age percentile were assessed at each clinical encounter over at least 4 years. Repeated measures analyses estimated the association of SES and ETS exposures with longitudinal clinical outcomes, adjusting for confounders.

RESULTS

Of 1797 participants, 1375 were eligible for analysis. Maternal education was high school or less in 28.1%, 26.8% had household income <$40 000, and 43.8% had Medicaid or no insurance. Maternal smoking after birth was present in 24.8%, more prevalent in household with low SES. In separate models, lower SES and ETS exposure were significantly associated with lower FEV₁% predicted, presence of crackles or wheezes, and lower weight percentile. In combined models, effect estimates for SES changed minimally after adjustment for ETS exposures, whereas estimates for ETS exposures were attenuated after adjusting for SES.

CONCLUSIONS

ETS exposure was disproportionately high in low SES families in this cohort of children with CF. Lower SES and ETS exposure had independent adverse effects on pulmonary and nutritional outcomes. Estimated effect of SES on FEV₁ decreased minimally after ETS adjustment, suggesting health disparity risks independent of ETS exposure.

Risk stratification model to detect early pulmonary disease in infants with cystic fibrosis diagnosed by newborn screening

OBJECTIVE

The clinical benefit of newborn screening (NBS) for cystic fibrosis (CF) has been primarily nutritional, with less overt respiratory impact. Identification of risk factors for infant CF lung disease could facilitate targeted interventions to improve pulmonary outcomes.

METHODS

This retrospective study evaluated socioeconomic information, clinical data, and results from routine infant pulmonary function testing (iPFT) of infants diagnosed with CF through NBS (N = 43) at a single CF center over a 4-year period (2008-2012). A five-item composite clinical score was developed and combined with socioeconomic indicators to facilitate identification of CF infants at increased risk of early-onset respiratory impairment.

RESULTS

Paternal education was positively associated with lung function (P = 0.02). Clinical score <7 (on a scale of 0-10) predicted diminished pulmonary measure (P < 0.005). Retrospective risk stratification by clinical score and paternal education identified CF infants at low, intermediate, or high risk of pulmonary disease. Forced expiratory volume (FEV_0.5 %, mean ± SD) averaged 115 ± 19% in the low-risk group, 97 ± 17% in the intermediate-risk group, and 90 ± 8% in the high-risk group (P < 0.005). Results were similar for mid-expiratory flows (FEF_25-75 %). Multiple regression analysis confirmed the predictive value of this risk stratification model of CF infant pulmonary health.

CONCLUSION

We combined socioeconomic and clinical data to risk-stratify CF infants for early-onset lung disease as quantified by iPFT. Our model showed significant differences in infant pulmonary function across risk groups. The developed tool offers an easily available, inexpensive, and non-invasive way to assess risk of respiratory decline in CF infants and identify those meriting targeted therapeutic attention. Pediatr Pulmonol. 2016;51:1168-1176. © 2016 Wiley Periodicals, Inc.

The role for neutrophil extracellular traps in cystic fibrosis autoimmunity

While respiratory failure in cystic fibrosis (CF) frequently associates with chronic infection by Pseudomonas aeruginosa, no single factor predicts the extent of lung damage in CF. To elucidate other causes, we studied the autoantibody profile in CF and rheumatoid arthritis (RA) patients, given the similar association of airway inflammation and autoimmunity in RA. Even though we observed that bactericidal permeability-increasing protein (BPI), carbamylated proteins, and citrullinated proteins all localized to the neutrophil extracellular traps (NETs), which are implicated in the development of autoimmunity, our study demonstrates striking autoantibody specificity in CF. Particularly, CF patients developed anti-BPI autoantibodies but hardly any anti-citrullinated protein autoantibodies (ACPA). In contrast, ACPA-positive RA patients exhibited no reactivity with BPI. Interestingly, anti-carbamylated protein autoantibodies (ACarPA) were found in both cohorts but did not cross-react with BPI. Contrary to ACPA and ACarPA, anti-BPI autoantibodies recognized the BPI C-terminus in the absence of posttranslational modifications. In fact, we discovered that P. aeruginosa-mediated NET formation results in BPI cleavage by P. aeruginosa elastase, which suggests a novel mechanism in the development of autoimmunity to BPI. In accordance with this model, autoantibodies associated with presence of P. aeruginosa on sputum culture. Finally, our results provide a role for autoimmunity in CF disease severity, as autoantibody levels associate with diminished lung function.

Phenotypic variability of R117H-CFTR expression within monozygotic twins

Whilst cystic fibrosis is a monogenic condition, variation in phenotype exists for the same CFTR genotype, which is influenced by multiple genetic and non-genetic (environmental) factors. The R117H-CFTR mutation has variability directly relating to in cis poly-thymidine alleles, producing a differing spectrum of disease. This paper provides evidence of extreme phenotype variability - including fertility status - in the context of male monogenetic twins, discussing mechanisms and highlighting the diagnostic and treatment challenges.

Features of Severe Liver Disease With Portal Hypertension in Patients With Cystic Fibrosis

BACKGROUND & AIMS

Liver disease is the third leading cause of death in patients with cystic fibrosis (CF), but features of patients with CF, severe liver disease, and portal hypertension have not been characterized fully.

METHODS

We performed a retrospective analysis of data from 561 patients with CF (63% male, 99% with pancreatic insufficiency), liver disease (hepatic parenchymal abnormalities consistent with cirrhosis, confirmed by imaging), and portal hypertension (esophageal varices, portosystemic collaterals, or splenomegaly), with no alternate causes of liver disease. All patients were enrolled in the Genetic Modifier Study of Severe CF Liver Disease at 76 international centers, from January 1999 through July 2013.

RESULTS

Male patients were diagnosed with liver disease at a younger age than female patients (10 vs 11 y; P = .01). Splenomegaly was observed in 99% of patients and varices in 71%. Levels of liver enzymes were near normal in most patients. Thrombocytopenia affected 70% of patients and was more severe in patients with varices (88 × 10(9)/L vs 145 × 10(9)/L; P < .0001). Ninety-one patients received liver transplants (16%), at a median age of 13.9 years. Compared with patients who did not receive liver transplants, patients who received liver transplants had lower platelet counts (78 × 10(9)/L vs 113 × 10(9)/L; P < .0001), higher international normalized ratios (P < .0001), and lower levels of albumin (P = .0002). The aminotransferase to platelet ratio index (APRi) and fibrosis index based on 4 factor (FIB-4) values were higher than the diagnostic thresholds for CF liver disease in 96% and in 90% of patients, respectively. Patients who received liver transplants or who had varices had higher APRi and FIB-4 values than patients who did not.

CONCLUSIONS

In patients with CF, severe liver disease develops early in childhood (approximately 10 years of age), and is more common in boys than in girls. Patients with varices and those who receive liver transplants have more abnormal platelet counts and APRi and FIB-4 scores.

Fine particulate matter exposure and initial Pseudomonas aeruginosa acquisition in cystic fibrosis

RATIONALE

Increasing evidence suggests that exposure to ambient air pollution contributes to the severity of cystic fibrosis (CF) respiratory disease in school-age children and adults; however, the effects of air pollution on young children with CF are poorly understood.

OBJECTIVES

To investigate the association of exposure to fine particulate matter less than 2.5 μm in aerodynamic diameter (PM2.5) and initial Pseudomonas aeruginosa acquisition in young children with CF.

METHODS

Retrospective analysis of initial Pseudomonas acquisition in children 6 years of age or younger, using Cystic Fibrosis Foundation National Patient Registry data from 2003 to 2009. PM2.5 exposure was estimated by inverse distance weighting methods based on air pollution monitors within 30 miles of place of residence, for the year before the patient's birth. Multivariable Weibull regression with interval-censored outcomes was done to evaluate the association of time to initial Pseudomonas acquisition and PM2.5 concentrations.

MEASUREMENTS AND MAIN RESULTS

A total of 3,575 children met inclusion criteria and 48% (n=1,711) acquired Pseudomonas at a median age of 15 months (25th-75th percentiles, 9-25 mo). An increase in PM2.5 exposure of 10 μg/m3 was associated with a 24% increased risk of Pseudomonas acquisition (95% confidence interval, 1-51%) during follow-up. Results were generally consistent across exposure metrics.

CONCLUSIONS

These results suggest that increased PM2.5 exposure is associated with earlier Pseudomonas acquisition in young children with CF and may play an important, previously unrecognized, role in the etiology of initial Pseudomonas infection.

Adherence to airway clearance therapy in pediatric cystic fibrosis: Socioeconomic factors and respiratory outcomes

OBJECTIVES

The evidence linking socioeconomic status (SES) and adherence in cystic fibrosis (CF) is inconclusive and focused on medication uptake. We examined associations between SES, adherence to airway clearance therapy (ACT), and CF respiratory outcomes.

STUDY DESIGN

Socioeconomic, clinical, and adherence data of CF patients (N = 110) at a single CF Center were evaluated in this cross-sectional observational study. SES was operationalized as maternal and paternal education and household income. Adherence to ACT was measured with utilization data from the high-frequency chest wall oscillation (HFCWO) device over 4-6 weeks. Statistical modeling was used to test three hypotheses: (H1) Higher SES is associated with higher ACT adherence; (H2) Higher SES is associated with better respiratory outcomes; and (H3) ACT adherence mediates the relationship between SES and respiratory outcomes.

RESULTS

In multinomial logistic regression, maternal college education, annual income >$50,000, and more adults in the household were independently related to better adherence (P < 0.05). Paternal college education, income >$100,000, and lack of exposure to smoking were independently related to higher lung function (P < 0.05). Current adherence to ACT with HFCWO was not associated with lung function over 12 months.

CONCLUSIONS

SES is associated both with ACT adherence and respiratory outcomes in pediatric CF patients. However, the link between SES and respiratory outcomes in this study was not mediated by adherence to ACT with HFCWO. These data emphasize the importance of socioeconomic resources and household environment for CF health. Family socio-demographic profiles can help identify patients at increased risk for ACT nonadherence.

Economic Burden And Health-Related Quality Of Life Of Patients With Cystic Fibrosis In Bulgaria

Objective:The aim of this study was to determine the economic burden from a societal perspective and health-related quality of life (HRQOL) of patients with cystic fibrosis (CF) in Bulgaria.

Materials and methods:We conducted a cross-sectional study of 33 patients with CF and 17 caregivers from Bulgaria. Data on socio-demographic characteristics, health resource utilisation, informal care, labor productivity losses and HRQOL were collected from questionnaires completed by patients or their caregivers. HRQOL was evaluated with the EuroQol 5-domain (EQ-5D-3L) questionnaire.

Results:Median annual costs of CF in Bulgaria were € 24 152 per patient in 2012 as a reference year. Median annual costs for children were found to be significantly higher than those for adults – € 31 945 vs. € 15 714 (p = 0.012). This outcome came from statistically significant differences in costs for main informal carer (p < 0.001) and costs for other informal carers (p = 0.022). As a single cost item, drugs had the biggest monetary impact. Median annual drug costs were € 13 059. Bulgarian CF patients showed low HRQOL results – 50 median VAS score and 0.592 median health utilities. A quarter of patients even rated their health state as worse than death.

Conclusion:CF patients from Eastern Europe remain a vulnerable population with risk factors for worse health outcomes. Our study provided a state-of-the art analysis that facilitates the elaboration, adoption and application of targeted public health policies to tackle CF-related problems at national and European level.

Novel personalized therapies for cystic fibrosis: treating the basic defect in all patients

Cystic fibrosis (CF) is the most common genetic life-shortening condition in Caucasians. Despite being a multi-organ disease, CF is classically diagnosed by symptoms of acute/chronic respiratory disease, with persistent pulmonary infections and mucus plugging of the airways and failure to thrive. These multiple symptoms originate from dysfunction of the CF transmembrane conductance regulator (CFTR) protein, a channel that mediates anion transport across epithelia. Indeed, establishment of a definite CF diagnosis requires proof of CFTR dysfunction, commonly through the so-called sweat Cl(-) test. Many drug therapies, including mucolytics and antibiotics, aim to alleviate the symptoms of CF lung disease. However, new therapies to modulate defective CFTR, the basic defect underlying CF, have started to reach the clinic, and several others are in development or in clinical trials. The novelty of these therapies is that, besides targeting the basic defect underlying CF, they are mutation specific. Indeed, even this monogenic disease is influenced by a large number of different genes and biological pathways as well as by environmental factors that are difficult to assess. Accordingly, every person with CF is unique and so functional assessment of patients' tissues ex vivo is key for diagnosing and predicting the severity of this disease. Of note, such assessment will also be crucial to assess drug responses, in order to effectively treat all CF patients. It is not because it is a monogenic disorder that personalized treatment for CF is much easier than for complex disorders.

Mechanisms of CFTR functional variants that impair regulated bicarbonate permeation and increase risk for pancreatitis but not for cystic fibrosis

CFTR is a dynamically regulated anion channel. Intracellular WNK1-SPAK activation causes CFTR to change permeability and conductance characteristics from a chloride-preferring to bicarbonate-preferring channel through unknown mechanisms. Two severe CFTR mutations (CFTRsev) cause complete loss of CFTR function and result in cystic fibrosis (CF), a severe genetic disorder affecting sweat glands, nasal sinuses, lungs, pancreas, liver, intestines, and male reproductive system. We hypothesize that those CFTR mutations that disrupt the WNK1-SPAK activation mechanisms cause a selective, bicarbonate defect in channel function (CFTRBD) affecting organs that utilize CFTR for bicarbonate secretion (e.g. the pancreas, nasal sinus, vas deferens) but do not cause typical CF. To understand the structural and functional requirements of the CFTR bicarbonate-preferring channel, we (a) screened 984 well-phenotyped pancreatitis cases for candidate CFTRBD mutations from among 81 previously described CFTR variants; (b) conducted electrophysiology studies on clones of variants found in pancreatitis but not CF; (c) computationally constructed a new, complete structural model of CFTR for molecular dynamics simulation of wild-type and mutant variants; and (d) tested the newly defined CFTRBD variants for disease in non-pancreas organs utilizing CFTR for bicarbonate secretion. Nine variants (CFTR R74Q, R75Q, R117H, R170H, L967S, L997F, D1152H, S1235R, and D1270N) not associated with typical CF were associated with pancreatitis (OR 1.5, p = 0.002). Clones expressed in HEK 293T cells had normal chloride but not bicarbonate permeability and conductance with WNK1-SPAK activation. Molecular dynamics simulations suggest physical restriction of the CFTR channel and altered dynamic channel regulation. Comparing pancreatitis patients and controls, CFTRBD increased risk for rhinosinusitis (OR 2.3, p<0.005) and male infertility (OR 395, p<<0.0001). WNK1-SPAK pathway-activated increases in CFTR bicarbonate permeability are altered by CFTRBD variants through multiple mechanisms. CFTRBD variants are associated with clinically significant disorders of the pancreas, sinuses, and male reproductive system.

Predictors and outcome of low initial forced expiratory volume in 1 second measurement in children with cystic fibrosis

OBJECTIVE

To identify the characteristics of children with cystic fibrosis with low initial forced expiratory volume in 1 second (FEV1) % predicted and to investigate their outcome.

STUDY DESIGN

Patients were categorized into low or high initial FEV1 groups using cluster analysis. Comparisons of the demographic and clinical data were performed between the 2 groups.

RESULTS

From 122 children, 21 clustered into the low and 101 into the high FEV1 group. The mean FEV1 was 69% ± 12% predicted for the low and 95% ± 12% predicted for the high FEV1 group (P < .001). The low FEV1 group had lower body mass index percentiles (P = .003), were hospitalized more frequently (P = .001), and had been on dornase alfa longer (P = .006). Low FEV1 group had more patients with positive cultures for Pseudomonas aeruginosa (P = .002) and Stenotrophomonas maltophilia (P < .001) and had more total number of cultures positive for mucoid P. aeruginosa (P = .009) and methicillin resistant Staphylococcus aureus + P. aeruginosa (P = .005). The low FEV1 group continued to have low FEV1 measurements, their FEV1 declined slower, required more hospitalizations per year (P = .01), and had more cultures for mucoid (P = .003) and nonmucoid P. aeruginosa (P = .02) ± methicillin resistant S. aureus (P = .002) in comparison with the high FEV1 group. Poor adherence was associated with lower initial FEV1 values in females, and early, rapid decline of FEV1 in males.

CONCLUSIONS

Some children with cystic fibrosis may present with poor lung function early in life and continue to have subnormal lung function associated with reduced body mass index, more frequent hospitalization, and higher rates of infection. Such children may benefit from careful evaluation and close follow-up.

Ozone is associated with an increased risk of respiratory exacerbations in patients with cystic fibrosis

Background

Tropospheric oxidant pollutants may injure the respiratory tract. Cystic fibrosis (CF) respiratory disease involves significant inflammation and excessive oxidative stress, and exposure to air pollutants can magnify the lung damage. The objective of this study was to investigate the association between the short-term variation in the concentration of air pollutants in metropolitan São Paulo, Brazil, and the occurrence of respiratory exacerbations in children and adolescents with CF.

Methods

A longitudinal panel of repeated measurements was obtained from 103 patients attending the outpatient center of our institution from September 6, 2006 through September 4, 2007. Daily concentrations of inhaled particulate matter, sulfur dioxide, nitrogen dioxide, ozone (O₃), carbon monoxide, and meteorologic variables, such as the minimum temperature and relative humidity, were evaluated. The generalized estimation equation model for binomial distribution was used to assess the impact of these measurements on the occurrence of acute respiratory exacerbations.

Results

In total, 103 patients with CF (median age, 8.9 years) made 408 visits, with a mean ± SD of 4 ± 1.74 visits per patient (range, 2-9). A respiratory disease exacerbation was diagnosed on 142 visits (38.4%). An interquartile range increase in the O₃ concentration (45.62 μg/m³) had a positive, delayed (2 days after exposure) effect on the risk of a respiratory exacerbation (relative risk = 1.86; 95% CI, 1.14-3.02).

Conclusions

This study demonstrates that exposure to short-term air pollution in a large urban center increases the risk of a pulmonary exacerbation in patients with CF.

Influenza vaccination in children with cystic fibrosis

Cystic fibrosis (CF) is an inherited autosomal recessive disease characterized by progressive pulmonary damage and respiratory failure. It is known that bacterial infections play a critical role in the development of significant lung damage, whereas the role of respiratory viruses in CF pulmonary exacerbations and the relationship between viral infections and the progression of lung damage are uncertain. Health authorities throughout the world recommend influenza vaccination for CF patients. The aim of this review is to analyze the impact of seasonal and pandemic influenza on CF patients and data concerning influenza vaccination in order to assess the current situation and identify areas for future study. As data are limited, further well-constructed clinical studies of the effectiveness of influenza vaccination on the main clinical outcome measures of pulmonary function and nutritional status in patients with CF are required.

The effect of social deprivation on clinical outcomes and the use of treatments in the UK cystic fibrosis population: a longitudinal study

Background

Poorer socioeconomic circumstances have been linked with worse outcomes in cystic fibrosis. We assessed whether a relation exists between social deprivation and individual's clinical and health-care outcomes.

Methods

We did a longitudinal registry study of the UK cystic fibrosis population younger than 40 years (8055 people with 49 337 observations for weight, the most commonly collected outcome, between Jan 1, 1996, and Dec 31, 2009). We assessed data for weight, height, body-mass index, percent predicted forced expiratory volume in 1 s (%FEV₁), risk of Pseudomonas aeruginosa colonisation, and the use of major cystic fibrosis treatment modalities. We used mixed effects models to assess the association between small-area deprivation and clinical and health-care outcomes, adjusting for clinically important covariates. We give continuous outcomes as mean differences, and binary outcomes as odds ratios, comparing extremes of deprivation quintile.

Findings

Compared with the least deprived areas, children from the most deprived areas weighed less (standard deviation [SD] score −0·28, 95% CI −0·38 to −0·18), were shorter (–0·31, −0·40 to −0·21, and had a lower body-mass index (–0·13, −0·22 to −0·04), were more likely to have chronic P aeruginosa infection (odds ratio 1·89, 95% CI 1·34 to 2·66), and have a lower %FEV₁ (–4·12 percentage points, 95% CI −5·01 to −3·19). These inequalities were apparent very early in life and did not widen thereafter. On a population level, after adjustment for disease severity, children in the most deprived quintile were more likely to receive intravenous antibiotics (odds ratio 2·52, 95% CI 1·92 to 3·17) and nutritional treatments (1·78, 1·44 to 2·20) compared with individuals in the least deprived quintile. Patients from the most disadvantaged areas were less likely to receive DNase or inhaled antibiotic treatment.

Interpretation

In the UK, children with cystic fibrosis from more disadvantaged areas have worse growth and lung function compared with children from more affluent areas, but these inequalities do not widen with advancing age. Clinicians consider deprivation status, as well as disease status, when making decisions about treatments, and this might mitigate some effects of social disadvantage.

Funding

Medical Research Council (UK).

Genetic modifiers of nutritional status in cystic fibrosis

BACKGROUND

Improved nutrition early in life is associated with better pulmonary function for patients with cystic fibrosis (CF). However, nutritional status is poorly correlated with the CFTR genotype.

OBJECTIVE

We investigated the extent to which modifier genes influence nutrition in children with CF.

DESIGN

BMI data were longitudinally collected from the CF Twin-Sibling Study and Cystic Fibrosis Foundation Patient Registry for twins and siblings from 2000 to 2010. A nutritional phenotype was derived for 1124 subjects by calculating the average BMI z score from 5-10 y of age (BMI-z(5to10)). The genetic contribution to the variation in BMI-z(5to10) (ie, heritability) was estimated by comparing the similarity of the phenotype in monozygous twins to that in dizygous twins and siblings. Linkage analysis identified potential modifier-gene loci.

RESULTS

The median BMI-z(5to10) was -0.07 (range: -3.89 to 2.30), which corresponded to the 47th CDC percentile. BMI-z(5to10) was negatively correlated with pancreatic insufficiency, history of meconium ileus, and female sex but positively correlated with later birth cohorts and lung function. Monozygous twins showed greater concordance for BMI-z(5to10) than did dizygous twins and siblings; heritability estimates from same-sex twin-only analyses ranged from 0.54 to 0.82. For 1010 subjects with pancreatic insufficiency, genome-wide significant linkage was identified on chromosomes 1p36.1 [log of odds (LOD): 5.3] and 5q14 (LOD: 5.1). These loci explained ≥16% and ≥15%, respectively, of the BMI variance.

CONCLUSIONS

The analysis of twins and siblings with CF indicates a prominent role for genes other than CFTR to BMI variation. Specifically, regions on chromosomes 1 and 5 appear to harbor genetic modifiers of substantial effect.