Risk factors for onset of persistent respiratory symptoms in children with cystic fibrosis

Clinical, economic, and societal burden of cystic fibrosis and the impact of the CFTR modulator, lumacaftor/ivacaftor: an assessment using linked registry data in Sweden

AIMS

We aimed to describe the clinical, economic, and societal burdens of cystic fibrosis (CF) and impact of CF transmembrane conductance regulator modulator (CFTRm) treatment on people with CF, caregivers, and healthcare systems.

MATERIAL AND METHODS

This retrospective study used linked real-world data from Swedish national population-based registries and the Swedish CF Quality Registry to assess clinical, economic, and societal burden and CFTR impact in CF. Records from people with CF and a ten-fold control population without CF matched by sex, birth year, and location were compared during 2019. Outcomes for a subset aged >6 years initiating lumacaftor/ivacaftor (LUM/IVA) in 2018 were compared 12 months pre- and post-treatment initiation.

RESULTS

People with CF (n = 743) had >10 times more inpatient and outpatient specialist visits annually vs controls (n = 7406). Those aged >18 had an additional 77·7 (95% CI: 70·3, 85·1) days of work absence, at a societal cost of €11,563 (95% CI: 10,463, 12,662), while caregivers of those aged <18 missed an additional 6.1 (5.0, 7.2) workdays. With LUM/IVA treatment, people with CF (n = 100) had significantly increased lung function (mean change in ppFEV1 [3·8 points; 95% CI: 1·1, 6·6]), on average 0·5 (95% CI: -0·8, -0·2) fewer pulmonary exacerbations and 45·2 (95% CI: 13·3, 77·2) fewer days of antibiotics. Days of work lost by caregivers of people with CF aged <18 decreased by 5·4 days (95% CI: 2·9, 7·9).

CONCLUSION

CF is associated with a high clinical economic and societal burden in Sweden. Improvements in clinical status observed in people with CF treated with LUM/IVA were reflected in reduced caregiver and societal burden.

Disparities in first evaluation of infants with cystic fibrosis since implementation of newborn screening

OBJECTIVE

We evaluated whether implementation of cystic fibrosis (CF) newborn screening (NBS) leads to equitable timeliness of initial evaluation. We compared age at first event (AFE, age at sweat test, encounter and/or care episode) between infants categorized as Black/African American, American Indian/ Native Alaskan, Asian, and/or Hispanic and/or other (Group 1) to White and not Hispanic infants (Group 2).

METHODS

This retrospective cohort study from the Cystic Fibrosis Foundation Patient Registry (CFFPR) included infants born 2010-2018. Race and ethnicity categories followed US Census definitions. The primary outcome was AFE; the secondary outcome was weight for age (WFA) z-score averaged 12 to < 24 months. We compared distributions by Wilcoxon rank-sum test and proportions by Chi-square or Fisher's exact tests. A nested cohort study used a linear mixed effects model of variables that affect WFA, chosen a priori, to evaluate associations with 1-year WFA z-score.

RESULTS

Among 6354 infants, 21% were in Group 1. Group 1 median AFE was 31 days (IQR 19, 49) and Group 2 was 22 days (IQR 14,36) (p< .001). Median WFA z-score at 1-2 years was lower in Group 1. In 3017 infants with complete data on variables of interest, AFE, Black race, CFTR variant class I-III, prematurity and public insurance were associated with lower 1-year WFA z-score.

CONCLUSIONS

Differences in AFE for infants with CF from historically marginalized groups may exacerbate long standing health disparities. We speculate that inequitable identification of CFTR gene variants and/or bias may influence timeliness of evaluation after an out-of-range NBS.

Prevalence and Determinants of Wheezing and Bronchodilatation in Children With Cystic Fibrosis: A Retrospective Cohort Study

Background

Many patients with cystic fibrosis (CF) wheeze, and are dubbed as having CF-asthma. Understanding the determinants of such wheezing may avoid unnecessary treatments and open newer treatment avenues.

Objectives

Main: To evaluate the prevalence and characteristics of wheezing and a positive bronchodilatory response (BDR) in children with CF. Secondary: To identify the predictive markers and the impact of current wheezing a positive BDR.

Methods

A retrospective single-center study in children with CF. We determined the characteristics of physician-reported wheeze in patients <6 years, and a BDR in patients aged 6-17 years. Anthropometric, lung function, laboratory, genetic and microbiological data were recorded in all groups. Variables were compared using the Chi2 and Student t-tests, and ANOVA.

Results

125 preschool and 69 school-aged children and adolescents with CF were included in the study. 71.2% of patients <6 years of age had had at least one episode of wheezing: 26.3% of patients were Transient Early Wheezers, 12.6% Late Onset Wheezers and 37.9% were Persistent Wheezers. The prevalence of a positive BDR was 73.5, 48.5, and 52.9% in the 6-8 years, 10-12 years, and 15-17 years age groups, respectively. Allergic factors were not predictive of wheezing in preschoolers. In the 6-8 years age group, the sum of wheal diameters of allergic skin prick tests (SPT, house dust mite + cat + dog dander) was greater in those with a BDR vs. no BDR (4 [2.0-8.8] vs. 1 [0-7.0] mm, p = 0.01). The presence of Pseudomonas aeruginosa in the bronchial secretions before 3 years of age was not significantly associated with either the presence of wheezing at the age of 6 years or a BDR in school-aged children and adolescents. The proportion of homozygous p.F508del patients was significantly lower in the group of patients who had wheezed by 6 years of age (60% vs. 72.7%, p = 0.009), but higher in the 6-8 years old group with a BDR vs. no BDR (64% vs. 36%, p = 0.04). Current wheezers at 6 years had a lower mean FEV1 vs. the non-current wheezers (91.5 ± 4.4% vs. 100.9 ± 2.4%; p = 0.047). Similarly, forced vital capacity (FVC) was significantly lower in the 6-8 years old group with BDR vs. no BDR (85 ± 19 vs. 101 ± 21%, p = 0.015).

Conclusion

Wheezing and BDR are very frequent findings in children with CF. Current wheeze at the age of 6 years was associated with worse lung function. Labeling wheezing in CF as "CF-Asthma" is misleading since the determinants are different, and may lead to inappropriate prescriptions of inhaled steroids.

Respiratory symptoms do not reflect functional impairment in early CF lung disease

BACKGROUND

Lung disease can develop within the first year of life in infants with cystic fibrosis (CF). However, the frequency and severity of respiratory symptoms in infancy are not known.

METHODS

We assessed respiratory symptoms in 50 infants with CF and 50 healthy matched controls from two prospective birth cohort studies. Respiratory symptoms and respiratory rate were documented by standardized weekly interviews throughout the first year. Infants performed multiple breath washout in the first weeks of life.

RESULTS

We analyzed 4552 data points (2217 in CF). Respiratory symptoms (either mild or severe) were not more frequent in infants with CF (OR:1.1;95% CI:[0.76, 1.59]; p=0.6). Higher lung clearance index and higher respiratory rate in infants with CF were not associated with respiratory symptoms.

CONCLUSIONS

We found no difference in respiratory symptoms between healthy and CF infants. These data indicate that early CF lung disease may not be captured by clinical presentation alone.

Epidemiologic Study of Cystic Fibrosis: 25 years of observational research

The Epidemiologic Study of Cystic Fibrosis (ESCF) was a prospective observational study of over 32,000 people with cystic fibrosis (CF) from 250 clinical care sites in North America from 1994 to 2005. Begun as a pharmacovigilance study in connection with the approval of dornase alfa in 1993, ESCF was open to all people with CF treated at any participating site in the United States or Canada. In addition to obtaining safety and effectiveness data on dornase alfa, ESCF collected encounter-based data to characterize the natural history and management of CF with a special focus on lung disease. During the study, 32,178 patients reported at least one encounter, contributing 869,136 encounters, 622,592 pulmonary function tests, 432,896 cultures, and 118,563 pulmonary exacerbations treated with intravenous antibiotics. Although ESCF data collection concluded in 2005, through a collaboration with the U.S. Cystic Fibrosis Foundation Patient Registry, additional follow-up data through 2017 was available for two-thirds of patients. This allowed for updating of CF genotype and survival information. Fifty-six peer-reviewed publications (cited over 3600 times) resulted from this study. In this manuscript we summarize the published ESCF manuscripts in thematic groups with key study findings and brief comments, and speculate on how ESCF findings will inform future data registries and patient care practices.

Risk factors for mortality before age 18 years in cystic fibrosis

BACKGROUND

Understanding early-life risk factors for childhood death in cystic fibrosis (CF) is important for clinical care, including the identification of effective interventions.

METHODS

Data from the Epidemiologic Study of Cystic Fibrosis (ESCF) collected 1994-2005 were linked with the Cystic Fibrosis Foundation Patient Registry (CFFPR) demographic and mortality data from 2013. Inclusion criteria were ≥1 visit annually at age 3-5 years and ≥1 FEV₁ measurement at age 6-8 years. Demographic data, nutritional parameters, pulmonary signs and symptoms, microbiology, and FEV₁ were evaluated as risk factors for death before age 18 years. Multivariable Cox proportional hazards regression was used to model the simultaneous effects of risk factors associated with death before age 18 years.

RESULTS

Among 5365 patients enrolled in ESCF who met inclusion criteria, 3880 (72%) were linked to the CFFPR. Among these, 191 (5.7%) died before age 18 years; median age at death was 13.4 ± 3.1 years. Multivariable regression showed clubbing, crackles, female sex, unknown CFTR genotype, minority race or ethnicity, Medicaid insurance (a proxy of low socioeconomic status), Pseudomonas aeruginosa on 2 or more cultures, and weight-for-age <50th percentile were significant risk factors for death regardless of inclusion of FEV₁ at age 6-8 years in the model.

CONCLUSION

We identified multiple risk factors for childhood death of patients with CF, all of which remained important after incorporating FEV₁ at age 6-8 years. Among the factors identified were the presence of clubbing or crackles at age 3-5 years, signs which are not routinely collected in registries.

An overview of international literature from cystic fibrosis registries. Part 5: Update 2012-2015 on lung disease

Patient registry data is a tool for defining the clinical course and risk factors in patients with less common diseases like Cystic Fibrosis. Forty-one registry-based reports on lung disease in Cystic Fibrosis were published between 2011 and 2015. The aim of this review is to describe and discuss the results of these reports, focusing on the risk factors for lung disease progression, specific microbiologic pathogens (e.g., non-tuberculous mycobacteria), disease complications, comparisons between registries of different countries, the impact of socio-economic status, and evaluation of benefits and costs of therapies. Techniques for improved clinical trial design were also studied. Pediatr Pulmonol. 2016;51:1251-1263. © 2016 Wiley Periodicals, Inc.

Clinical characteristics and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in children with cystic fibrosis from a center with a high MRSA prevalence

BACKGROUND

We describe the clinical characteristics and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in children with cystic fibrosis (CF) from the U.S. CF center with the highest MRSA prevalence.

METHODS

Medical records of children with CF were retrospectively reviewed from 1997-2009. MRSA clinical isolates from 2007-2009 were analyzed by polymerase chain reaction and pulsed field gel electrophoresis.

RESULTS

The prevalence of MRSA was 1% in 1997 and 49% in 2009. Fifty-five children (26%) had persistent MRSA infection. Sixty-eight percent of MRSA isolates were hospital-associated (HA) MRSA, of which 52% were pulsed-field type USA 100. Ninety-three percent of HA MRSA isolates were clindamycin resistant. Twelve children acquired MRSA before 1 year of age, 83% of whom were hospitalized prior to acquisition of MRSA. Ten of 11 sibling pairs carried indistinguishable MRSA strains. Children with persistent MRSA were hospitalized more often (P = .01), required inhaled medications more frequently (P = .01), and had higher rates of Pseudomonas aeruginosa coinfection (P < .001).

CONCLUSION

MRSA prevalence in children with CF is increasing, and most children are infected with HA MRSA. Exposure to health care facilities and gastrointestinal surgeries may facilitate early acquisition of MRSA. Siblings carry indistinguishable MRSA strains, indicating household transmission of MRSA. Children with persistent MRSA had worse pulmonary morbidity. Coinfection with MRSA and P aeruginosa is likely associated with further increased pulmonary morbidity.

Prevalence of meconium ileus marks the severity of mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene

RATIONALE

Meconium ileus (MI) is a perinatal complication in cystic fibrosis (CF), which is only minimally influenced by environmental factors. We derived and examined MI prevalence (MIP) scores to assess CFTR phenotype-phenotype correlation for severe mutations.

METHOD

MIP scores were established using a Canadian CF population (n = 2,492) as estimates of the proportion of patients with MI among all patients carrying the same CFTR mutation, focusing on patients with p.F508del as the second allele. Comparisons were made to the registries from the US CF Foundation (n = 43,432), Italy (Veneto/Trentino/Alto Adige regions) (n = 1,788), and Germany (n = 3,596).

RESULTS

The prevalence of MI varied among the different registries (13-21%). MI was predominantly prevalent in patients with pancreatic insufficiency carrying "severe" CFTR mutations. In this severe spectrum MIP scores further distinguished between mutation types, for example, G542X (0.31) with a high, F508del (0.22) with a moderate, and G551D (0.08) with a low MIP score. Higher MIP scores were associated with more severe clinical phenotypes, such as a lower forced expiratory volume in 1 second (P = 0.01) and body mass index z score (P = 0.04).

CONCLUSIONS

MIP scores can be used to rank CFTR mutations according to their clinical severity and provide a means to expand delineation of CF phenotypes.Genet Med 18 4, 333-340.

Early childhood wheezing is associated with lower lung function in cystic fibrosis

OBJECTIVE

To study the association between wheezing in children with cystic fibrosis (CF) and lung function in later life.

METHODS

We used data from the Epidemiologic Study of CF, a longitudinal observational study from 1994 to 2005. Wheezing phenotypes were defined as: no wheezing in the first 6 years of life (NW), transient wheezing (TW; wheezing <3 years old, but no wheezing after 3), late wheezing (LW; wheezing only after age 3 years), and persistent wheezing (PW; wheezing both before and after age 3 years). A linear regression model was developed predicting the best forced expiratory volume in 1 sec (FEV1 ) at age 6 or 7 years (6 to <8) for each wheezing phenotype.

RESULTS

A total of 1302 children met the cohort inclusion criteria; 61% of the cohort had wheezing in the first 6 years of life. A history of any wheezing in the first 6 years of life was associated with a significantly lower FEV1 at 6 to <8 years compared to children with NW. The FEV1 of children with NW at age 6 to <8 years was 104% predicted, whereas the mean FEV1 in TW, LW, and PW groups was 98%, 100%, and 96% predicted, respectively (P < 0.05 compared to NW).

CONCLUSIONS

Childhood wheezing in CF is common and is associated with lower lung function at age 6 to <8 years. Our results identify a clinical feature in early childhood CF associated with lower lung function in later life.

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.

Pseudomonas aeruginosa utilizes the type III secreted toxin ExoS to avoid acidified compartments within epithelial cells

Invasive Pseudomonas aeruginosa (PA) can enter epithelial cells wherein they mediate formation of plasma membrane bleb-niches for intracellular compartmentalization. This phenotype, and capacity for intracellular replication, requires the ADP-ribosyltransferase (ADPr) activity of ExoS, a PA type III secretion system (T3SS) effector protein. Thus, PA T3SS mutants lack these capacities and instead traffic to perinuclear vacuoles. Here, we tested the hypothesis that the T3SS, via the ADPr activity of ExoS, allows PA to evade acidic vacuoles that otherwise suppress its intracellular viability. The acidification state of bacteria-occupied vacuoles within infected corneal epithelial cells was studied using LysoTracker to visualize acidic, lysosomal vacuoles. Steady state analysis showed that within cells wild-type PAO1 localized to both membrane bleb-niches and vacuoles, while both exsA (transcriptional activator) and popB (effector translocation) T3SS mutants were only found in vacuoles. The acidification state of occupied vacuoles suggested a relationship with ExoS expression, i.e. vacuoles occupied by the exsA mutant (unable to express ExoS) were more often acidified than either popB mutant or wild-type PAO1 occupied vacuoles (p < 0.001). An exoS-gfp reporter construct pJNE05 confirmed that high exoS transcriptional output coincided with low occupation of acidified vacuoles, and vice versa, for both popB mutants and wild-type bacteria. Complementation of a triple effector null mutant of PAO1 with exoS (pUCPexoS) reduced the number of acidified bacteria-occupied vacuoles per cell; pUCPexoSE381D which lacks ADPr activity did not. The H⁺-ATPase inhibitor bafilomycin rescued intracellular replication to wild-type levels for exsA mutants, showing its viability is suppressed by vacuolar acidification. Taken together, the data show that the mechanism by which ExoS ADPr activity allows intracellular replication by PA involves suppression of vacuolar acidification. They also show that variability in ExoS expression by wild-type PA inside cells can differentially influence the fate of individual intracellular bacteria, even within the same cell.

Translocon-independent intracellular replication by Pseudomonas aeruginosa requires the ADP-ribosylation domain of ExoS

Pseudomonas aeruginosa, a significant cause of human morbidity and mortality, uses a type 3 secretion system (T3SS) to inject effector toxins into host cells. We previously reported that P. aeruginosa uses ADP-ribosyltransferase (ADPr) activity of the T3SS effector ExoS for intracellular replication. T3SS translocon (ΔpopB)-mutants, which can export, but not translocate effectors across host membranes, retained intracellular replication. We hypothesized that secreted effectors mediate translocon-independent intracellular replication. Translocon mutants of PAO1 lacking one or more of its three known effectors (ExoS, ExoT and ExoY) were used. All translocon mutants, irrespective of effectors expressed, localized to intracellular vacuoles. Translocon-effector null mutants and translocon-exoS mutants showed defective intracellular replication. Mutants in exoT, exoY or both replicated as efficiently as translocon mutants expressing all effectors. Complementation of translocon-effector null mutants with native exoS or a membrane localization domain mutant of exoS, but not the ADPr mutant exoS (pUCPexoSE381D), restored intracellular replication, correlating with increased bacteria per vacuole. Thus, P. aeruginosa is capable of intravacuolar replication that requires ExoS ADPr activity, but not the translocon. These data suggest that T3SS effectors can participate in pathogenesis without translocon-mediated translocation across host membranes, and that intracellular bacteria can contribute to P. aeruginosa pathogenesis within epithelial cells.