Use of FEV1 in cystic fibrosis epidemiologic studies and clinical trials: A statistical perspective for the clinical researcher

BACKGROUND

Forced expiratory volume in 1s (FEV₁) is an established marker of cystic fibrosis (CF) disease progression that is used to capture clinical course and evaluate therapeutic efficacy. The research community has established FEV₁ surveillance data through a variety of observational data sources such as patient registries, and there is a growing pipeline of new CF therapies demonstrated to be efficacious in clinical trials by establishing improvements in FEV₁.

RESULTS

In this review, we summarize from a statistical perspective the clinical relevance of FEV₁ based on its association with morbidity and mortality in CF, its role in epidemiologic studies of disease progression and comparative effectiveness, and its utility in clinical trials. In addition, we identify opportunities to advance epidemiologic research and the clinical development pipeline through further statistical considerations.

CONCLUSIONS

Our understanding of CF disease course, therapeutics, and clinical care has evolved immensely in the past decades, in large part due to the thoughtful application of rigorous research methods and meaningful clinical endpoints such as FEV₁. A continued commitment to conduct research that minimizes the potential for bias, maximizes the limited patient population, and harmonizes approaches to FEV₁ analysis while maintaining clinical relevance, will facilitate further opportunities to advance CF care.

Assessment of safety and efficacy of long-term treatment with combination lumacaftor and ivacaftor therapy in patients with cystic fibrosis homozygous for the F508del-CFTR mutation (PROGRESS): a phase 3, extension study

BACKGROUND

The 24-week safety and efficacy of lumacaftor/ivacaftor combination therapy was shown in two randomised controlled trials (RCTs)-TRAFFIC and TRANSPORT-in patients with cystic fibrosis who were aged 12 years or older and homozygous for the F508del-CFTR mutation. We aimed to assess the long-term safety and efficacy of extended lumacaftor/ivacaftor therapy in this group of patients in PROGRESS, the long-term extension of TRAFFIC and TRANSPORT.

METHODS

PROGRESS was a phase 3, parallel-group, multicentre, 96-week study of patients who completed TRAFFIC or TRANSPORT in 191 sites in 15 countries. Patients were eligible if they were at least 12 years old with cystic fibrosis and homozygous for the F508del-CFTR mutation. Exclusion criteria included any comorbidity or laboratory abnormality that, in the opinion of the investigator, might confound the results of the study or pose an additional risk in administering the study drug to the participant, history of drug intolerance, and history of poor compliance with the study drug. Patients who previously received active treatment in TRANSPORT or TRAFFIC remained on the same dose in PROGRESS. Patients who had received placebo in TRANSPORT or TRAFFIC were randomly assigned (1:1) to receive lumacaftor (400 mg every 12 h)/ivacaftor (250 mg every 12 h) or lumacaftor (600 mg once daily)/ivacaftor (250 mg every 12 h). The primary outcome was to assess the long-term safety of combined therapy. The estimated annual rate of decline in percent predicted FEV₁ (ppFEV₁) in treated patients was compared with that of a matched registry cohort. Efficacy analyses were based on modified intention-to-treat, such that data were included for all patients who were randomly assigned and received at least one dose of study drug. This study is registered with ClinicalTrials.gov, number NCT01931839.

FINDINGS

Between Oct 24, 2013, and April 7, 2016, 1030 patients from the TRANSPORT and TRAFFIC studies enrolled in PROGRESS, and 1029 received at least one dose of study drug. 340 patients continued treatment with lumacaftor 400 mg every 12 h/ivacaftor 250 mg every 12 h; 176 patients who had received placebo in the TRANSPORT or TRAFFIC studies initiated treatment with lumacaftor 400 mg every 12 h/ivacaftor 250 mg every 12 h, the commercially available dose, for which data are presented. The most common adverse events were infective pulmonary exacerbations, cough, increased sputum, and haemoptysis. Modest blood pressure increases seen in TRAFFIC and TRANSPORT were also observed in PROGRESS. For patients continuing treatment, the mean change from baseline in ppFEV₁ was 0·5 (95% CI -0·4 to 1·5) at extension week 72 and 0·5 (-0·7 to 1·6) at extension week 96; change in BMI was 0·69 (0·56 to 0·81) at extension week 72 and 0·96 (0·81 to 1·11) at extension week 96. The annualised pulmonary exacerbation rate in patients continuing treatment through extension week 96 (0·65, 0·56 to 0·75) remained lower than the placebo rate in TRAFFIC and TRANSPORT. The annualised rate of ppFEV₁ decline was reduced in lumacaftor/ivacaftor-treated patients compared with matched controls (-1·33, -1·80 to -0·85 vs -2·29, -2·56 to -2·03). The efficacy and safety profile of the lumacaftor 600 mg once daily/ivacaftor 250 mg every 12 h groups was generally similar to that of the lumacaftor 400 mg every 12 h/ivacaftor 250 mg every 12 h groups.

INTERPRETATION

The long-term safety profile of lumacaftor/ivacaftor combination therapy was consistent with previous RCTs. Benefits continued to be observed with longer-term treatment, and lumacaftor/ivacaftor was associated with a 42% slower rate of ppFEV₁ decline than in matched registry controls.

FUNDING

Vertex Pharmaceuticals Incorporated.

Change in Pseudomonas aeruginosa prevalence in cystic fibrosis adults over time

Background

Little is known about risk factors for chronic and mucoid Pseudomonas aeruginosa (Pa) infection in cystic fibrosis (CF) adults, and whether the prevalence is changing.

Methods

We employed a retrospective cohort to analyze data from a single adult CF center (2002 to 2012). Regression models were used to assess independent predictors and change in prevalence of chronic and mucoid Pa infection over time.

Results

The odds ratio of mucoid Pa infection was significantly less in individuals with better baseline lung function (OR 0.84,95%CI:0.77–0.92) and those diagnosed after the age of 25 (OR 0.21, 95%CI:0.05–0.95). The prevalence of chronic Pa and mucoid Pa decreased during the time interval. After adjusting for confounders, the observed decrease in chronic and mucoid Pa between 2002 and 2012 was no longer significant.

Conclusions

The prevalence of chronic and mucoid Pa is decreasing. Larger studies are needed to confirm these regional trends and their significance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-016-0333-y) contains supplementary material, which is available to authorized users.

Variability in Management of First Cerebrospinal Fluid Shunt Infection: A Prospective Multi-Institutional Observational Cohort Study

OBJECTIVES

To describe the variation in approaches to surgical and antibiotic treatment for first cerebrospinal fluid (CSF) shunt infection and adherence to Infectious Diseases Society of America (IDSA) guidelines.

STUDY DESIGN

We conducted a prospective cohort study of children undergoing treatment for first CSF infection at 7 Hydrocephalus Clinical Research Network hospitals from April 2008 through December 2012. Univariate analyses were performed to describe the study population.

RESULTS

A total of 151 children underwent treatment for first CSF shunt-related infection. Most children had undergone initial CSF shunt placement before the age of 6 months (n =  98, 65%). Median time to infection after shunt surgery was 28 days (IQR 15-52 days). Surgical management was most often shunt removal with interim external ventricular drain placement, followed by new shunt insertion (n = 122, 81%). Median time from first negative CSF culture to final surgical procedure was 14 days (IQR 10-21 days). Median duration of intravenous (IV) antibiotic use duration was 19 days (IQR 12-28 days). For 84 infections addressed by IDSA guidelines, 7 (8%) met guidelines and 61 (73%) had longer duration of IV antibiotic use than recommended.

CONCLUSIONS

Surgical treatment for infection frequently adheres to IDSA guidelines of shunt removal with external ventricular drain placement followed by new shunt insertion. However, duration of IV antibiotic use in CSF shunt infection treatment was consistently longer than recommended by the 2004 IDSA guidelines.

Microbiological efficacy of early MRSA treatment in cystic fibrosis in a randomised controlled trial

OBJECTIVE

To evaluate microbiological effectiveness, that is, culture negativity of a non-blinded eradication protocol (Rx) compared with observation (Obs) in clinically stable cystic fibrosis participants with newly positive methicillin resistant Staphylococcusaureus (MRSA) cultures.

DESIGN

This non-blinded trial randomised participants ages 4-45 years with first or early (≤2 positive cultures within 3 years) MRSA-positive culture without MRSA-active antibiotics within 4 weeks 1:1 to Rx or Obs. The Rx protocol was: oral trimethoprim-sulfamethoxazole or if sulfa-allergic, minocycline plus oral rifampin; chlorhexidine mouthwash for 2 weeks; nasal mupirocin and chlorhexidine body wipes for 5 days and environmental decontamination for 21 days. The primary end point was MRSA culture status at day 28.

RESULTS

Between 1 April 2011 to September 2014, 45 participants (44% female, mean age 11.5 years) were randomised (24 Rx, 21 Obs). At day 28, 82% (n=18/22) of participants in the Rx arm compared with 26% (n=5/19) in the Obs arm were MRSA-negative. Adjusted for interim monitoring, this difference was 52% (95% CI 23% to 80%, p<0.001). Limiting analyses to participants who were MRSA-positive at the screening visit, 67% (8/12) in the Rx arm and 13% (2/15) in the Obs arm were MRSA-negative at day 28, adjusted difference: 49% (95% CI 22% to 71%, p<0.001). Fifty-four per cent in the Rx arm compared with 10% participants in the Obs arm remained MRSA-negative through day 84. Mild gastrointestinal side effects were higher in the Rx arm.

CONCLUSIONS

This MRSA eradication protocol for newly acquired MRSA demonstrated microbiological efficacy with a large treatment effect.

TRIAL REGISTRATION NUMBER

NCT01349192.

Advancing clinical development pathways for new CFTR modulators in cystic fibrosis

Cystic fibrosis (CF) is a life-shortening genetic disease affecting approximately 70,000 individuals worldwide. Until recently, drug development efforts have emphasised therapies treating downstream signs and symptoms resulting from the underlying CF biological defect: reduced function of the CF transmembrane conductance regulator (CFTR) protein. The current CF drug development landscape has expanded to include therapies that enhance CFTR function by either restoring wild-type CFTR protein expression or increasing (modulating) the function of mutant CFTR proteins in cells. To date, two systemic small-molecule CFTR modulators have been evaluated in pivotal clinical trials in individuals with CF and specific mutant CFTR genotypes that have led to regulatory review and/or approval. Advances in the discovery of CFTR modulators as a promising new class of therapies have been impressive, yet work remains to develop highly effective, disease-modifying modulators for individuals of all CF genotypes. The objectives of this review are to outline the challenges and opportunities in drug development created by systemic genotype-specific CFTR modulators, highlight the advantages of sweat chloride as an established biomarker of CFTR activity to streamline early-phase development and summarise options for later phase clinical trial designs that respond to the adoption of approved genotype-specific modulators into standard of care. An optimal development framework will be needed to move the most promising therapies efficiently through the drug development pipeline and ultimately deliver efficacious and safe therapies to all individuals with CF.

Predictors of non-referral of patients with cystic fibrosis for lung transplant evaluation in the United States

BACKGROUND

Lung transplantation is an intervention that improves survival for adult patients with cystic fibrosis (CF). Some patients with CF are never referred for lung transplant evaluation despite meeting physiologic criteria for referral.

METHODS

We performed a retrospective analysis of adult patients (≥18years of age) in the Cystic Fibrosis Foundation Patient Registry (CFFPR), eligible for their first evaluation for lung transplantation during the years 2001-2008 based on FEV1<30% predicted in two consecutive years.

RESULTS

Within the CFFPR, 1240 patients met eligibility criteria. Eight hundred and nine (65.2%) were referred for lung transplant evaluation, and 431 (34.8%) were not referred. In a multivariable model, Medicaid insurance (OR 1.79, 95% CI 1.29-2.47), older age (per 5year increase; OR 1.25, 95% CI 1.13-1.39), lack of high school graduate education (OR 2.27, 95% CI 1.42-3.64), and Burkholderia cepacia complex sputum culture positivity (OR 2.48, 95% CI 1.50-4.12) were associated with non-referral, while number of pulmonary exacerbations (OR 0.93, 95% CI 0.87-0.99) and supplemental oxygen use (OR 0.59, 95% CI 0.43-0.81) were associated with increased referral.

CONCLUSIONS

Despite meeting lung function criteria for lung transplant evaluation, 35% of patients with CF had not yet been referred to a lung transplant center. Predictors of non-referral included markers of low socioeconomic status, older age and B. cepacia complex sputum culture. Further work is needed to understand the outcomes for non-referred patients in order to refine referral recommendations in this population.

In Vitro Antibiotic Susceptibility of Initial Pseudomonas aeruginosa Isolates From United States Cystic Fibrosis Patients

Chronic antibiotic suppression of cystic fibrosis (CF) infections has increased in the United States, as has isolation of Pseudomonas aeruginosa with reduced antibiotic susceptibility. However, analysis of the susceptibilities of 193 initial P aeruginosa clinical isolates suggests that antibiotic susceptibilities are comparable with wild-type strains despite expanded antipseudomonal treatment in the CF community.

Impact of Sustained Eradication of New Pseudomonas aeruginosa Infection on Long-term Outcomes in Cystic Fibrosis

BACKGROUND

Pseudomonas aeruginosa (Pa) is the most important pathogen infecting the airways in individuals with cystic fibrosis. A key question is whether children with newly acquired Pa infection who are able to achieve sustained eradication after early antipseudomonal therapy demonstrate improved long-term health outcomes compared with those who are unable to achieve a sustained microbiologic response.

METHODS

This cohort study utilized observational follow-up data on children participating in the Early Pseudomonas Infection Control trial who received standardized therapy for newly acquired Pa. Sustained eradicators were defined as those who maintained Pa-negative cultures for 12 months after initial antipseudomonal therapy. Associations between eradication status and outcomes were assessed.

RESULTS

Of the 249 trial participants included in the study, 172 (69%) achieved sustained eradication of Pa during the trial (sustained eradicators). Over the median 5-year follow-up, sustained eradicators had a 74% reduced risk of developing chronic Pa (hazard ratio [HR], 0.26; 95% confidence interval [CI], .17-.40) and a 57% reduced risk of mucoidy (HR, 0.43; 95% CI, .25-.73) compared with nonsustained eradicators. Sustained eradicators had significantly less anti-Pa antibiotic usage during follow-up compared with nonsustained eradicators. There was no association between eradication status and clinical outcomes including rate of exacerbation and lung function decline.

CONCLUSIONS

This is the first study to quantify the long-term durability of microbiological response associated with early antipseudomonal therapy, demonstrating the critical importance of optimizing antipseudomonal therapies during early Pa infection. The clinical impact of failure to achieve sustained Pa eradication remains unclear, however, and may be confounded by anti-Pa antibiotic usage.

CLINICAL TRIALS REGISTRATION

NCT00097773.

Heterogeneity and disparities in the use of exception scores in pediatric liver allocation

Physicians apply for Model for End-Stage Liver Disease/Pediatric End-Stage Liver Disease exception points on a case-by-case basis to improve an individual patient's chances of receiving a liver transplant. This retrospective cohort study describes trends in the use of exceptions among the pediatric liver waitlist population with chronic liver disease. The cohort (n = 3728) included all children with a diagnosis of chronic liver disease listed in the United Network for Organ Sharing transplant database for first isolated liver transplant between February 27, 2002 and March 31, 2013. Exception score requests were common (34%); 90% of requests were approved. The rate of exception score requests in 2013 was five times that of 2002 (incident rate ratios [IRR] 5.25, 95% confidence interval [CI] 3.19-8.63, p < 0.01). Patients of non-White race had exception score request rates 13% lower than patients of White race (IRR 0.87, 95% CI 0.77-0.98, p = 0.02). Older patients had lower rates of exception score requests than younger patients (p = 0.03). Request rates varied by region. Time spent at an active exception status nearly tripled the hazard rate for transplantation (hazard ratio = 2.90, 95% CI 2.62-3.21, p < 0.01). There is disparity in use of exceptions by race that is not explained by clinical disease severity, diagnosis, geography or other demographic factors.

Early attained weight and length predict growth faltering better than velocity measures in infants with CF

BACKGROUND

CF infants often do not grow as expected which adversely affects later clinical outcomes, thus sensitive early measures of growth deficiency are important. This study compared attained growth for age with velocity standards to determine which better predicts growth deficits at 24 months of age.

METHODS

Growth deficiency in infancy based on weight and length velocity, and attained growth was calculated for 1992 infants in the US CF Foundation National Registry using the World Health Organization (WHO) and US growth standards. One, two and three month increments were used for calculating velocity and pooled for each age interval. Sensitivity and specificity of early indicators to predict growth deficiency at 24 months were calculated.

RESULTS

Observed prevalence of weight deficiency (<10th percentile) during the first year of life was 26.8% higher (95% CI=(25.6, 28.1%), p<0.001) on average when measured by attained weight for age than velocity. Attained weight for age at four months was a more sensitive predictor of diminished weight for age (<10th percentile) at 24 months (sensitivity=100%, 95% CI=(87, 100%)) than weight velocity (sensitivity=40%, 95% CI=(23, 59%)). Attained length at four months was more sensitive to detecting subsequent stunting (<10th percentile length for age) (77%, 95% CI=(62, 87%)) than length velocity (30%, 95% CI=(19, 45%)).

CONCLUSIONS

In CF infancy, attained weight or length is more sensitive than velocity-based definitions for predicting subsequent diminished growth.

Pseudomonas aeruginosa in cystic fibrosis patients with G551D-CFTR treated with ivacaftor

BACKGROUND

Ivacaftor improves outcomes in cystic fibrosis (CF) patients with the G551D mutation; however, effects on respiratory microbiology are largely unknown. This study examines changes in CF respiratory pathogens with ivacaftor and correlates them with baseline characteristics and clinical response.

METHODS

The G551D Observational Study enrolled a longitudinal observational cohort of US patients with CF aged 6 years and older with at least 1 copy of the G551D mutation. Results were linked with retrospective and prospective culture data in the US Cystic Fibrosis Foundation's National Patient Registry. Pseudomonas aeruginosa infection category in the year before and year after ivacaftor was compared and correlated with clinical findings.

RESULTS

Among 151 participants prescribed ivacaftor, 29% (26/89) who were culture positive for P. aeruginosa the year prior to ivacaftor use were culture negative the year following treatment; 88% (52/59) of those P. aeruginosa free remained uninfected. The odds of P. aeruginosa positivity in the year after ivacaftor compared with the year prior were reduced by 35% (odds ratio [OR], 0.65; P < .001). Ivacaftor was also associated with reduced odds of mucoid P. aeruginosa (OR, 0.77; P = .013) and Aspergillus (OR, 0.47; P = .039), but not Staphylococcus aureus or other common CF pathogens. Patients with intermittent culture positivity and higher forced expiratory volume in 1 second (FEV1) were most likely to turn culture negative. Reduction in P. aeruginosa was not associated with change in FEV1, body mass index, or hospitalizations.

CONCLUSIONS

Pseudomonas aeruginosa culture positivity was significantly reduced following ivacaftor treatment. Efficacious CFTR modulation may contribute to lower frequency of culture positivity for P. aeruginosa and other respiratory pathogens, particularly in patients with less established disease.

Pseudomonas aeruginosa in vitro phenotypes distinguish cystic fibrosis infection stages and outcomes

RATIONALE

Pseudomonas aeruginosa undergoes phenotypic changes during cystic fibrosis (CF) lung infection. Although mucoidy is traditionally associated with transition to chronic infection, we hypothesized that additional in vitro phenotypes correlate with this transition and contribute to disease.

OBJECTIVES

To characterize the relationships between in vitro P. aeruginosa phenotypes, infection stage, and clinical outcomes.

METHODS

A total of 649 children with CF and newly identified P. aeruginosa were followed for a median 5.4 years during which a total of 2,594 P. aeruginosa isolates were collected. Twenty-six in vitro bacterial phenotypes were assessed among the isolates, including measures of motility, exoproduct production, colony morphology, growth, and metabolism.

MEASUREMENTS AND MAIN RESULTS

P. aeruginosa phenotypes present at the time of culture were associated with both stage of infection (new onset, intermittent, or chronic) and the primary clinical outcome, occurrence of a pulmonary exacerbation (PE) in the subsequent 2 years. Two in vitro P. aeruginosa phenotypes best distinguished infection stages: pyoverdine production (31% of new-onset cultures, 48% of intermittent, 69% of chronic) and reduced protease production (31%, 39%, and 65%, respectively). The best P. aeruginosa phenotypic predictors of subsequent occurrence of a PE were mucoidy (odds ratio, 1.75; 95% confidence interval, 1.19-2.57) and reduced twitching motility (odds ratio, 1.43; 95% confidence interval, 1.11-1.84).

CONCLUSIONS

In this large epidemiologic study of CF P. aeruginosa adaptation, P. aeruginosa isolates exhibited two in vitro phenotypes that best distinguished early and later infection stages. Among the many phenotypes tested, mucoidy and reduced twitching best predicted subsequent PE. These phenotypes indicate potentially useful prognostic markers of transition to chronic infection and advancing lung disease.

Clinical mechanism of the cystic fibrosis transmembrane conductance regulator potentiator ivacaftor in G551D-mediated cystic fibrosis

RATIONALE

Ivacaftor is a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator recently approved for patients with CF age 6 and older with the G551D mutation.

OBJECTIVES

To evaluate ivacaftor in a postapproval setting and determine mechanism of action and response of clinically relevant markers.

METHODS

We conducted a longitudinal cohort study in 2012-2013 in G551D CF patients age 6 and older with no prior exposure to ivacaftor. Study assessments were performed at baseline, 1, 3, and 6 months after ivacaftor initiation. Substudies evaluated mucociliary clearance, β-adrenergic sweat secretion rate, gastrointestinal pH, and sputum inflammation and microbiology Measurements and Main Results: A total of 151 of 153 subjects were prescribed ivacaftor and 88% completed the study through 6 months. FEV1 % predicted improved from baseline to 6 months (mean absolute change, 6.7%; P < 0.001). Similarly, body mass index improved from baseline to 6 months (mean change, 0.8 kg/m(2); P < 0.001). Sweat chloride decreased from baseline to 6 months (mean change, -53.8 mmol/L; 95% confidence interval, -57.7 to -49.9; P < 0.001), reflecting augmented CFTR function. There was significant improvement in hospitalization rate (P < 0.001) and Pseudomonas aeruginosa burden (P < 0.01). Significant improvements in mucociliary clearance (P < 0.001), gastrointestinal pH (P = 0.001), and microbiome were also observed, providing clinical mechanisms underlying the therapeutic benefit of ivacaftor.

CONCLUSIONS

Significant clinical and physiologic improvements were observed on initiation of ivacaftor in a broad patient population, including reduced infection with P. aeruginosa. Biomarker studies substantially improve the understanding of the mechanistic consequences of CFTR modulation on pulmonary and gastrointestinal physiology.

Risk factors for first cerebrospinal fluid shunt infection: findings from a multi-center prospective cohort study

OBJECTIVE

To quantify the extent to which cerebrospinal fluid (CSF) shunt revisions are associated with increased risk of CSF shunt infection, after adjusting for patient factors that may contribute to infection risk.

STUDY DESIGN

We used the Hydrocephalus Clinical Research Network registry to assemble a large prospective 6-center cohort of 1036 children undergoing initial CSF shunt placement between April 2008 and January 2012. The primary outcome of interest was first CSF shunt infection. Data for initial CSF shunt placement and all subsequent CSF shunt revisions prior to first CSF shunt infection, where applicable, were obtained. The risk of first infection was estimated using a multivariable Cox proportional hazard model accounting for patient characteristics and CSF shunt revisions, and is reported using hazard ratios (HRs) with 95% CI.

RESULTS

Of the 102 children who developed first infection within 12 months of placement, 33 (32%) followed one or more CSF shunt revisions. Baseline factors independently associated with risk of first infection included: gastrostomy tube (HR 2.0, 95% CI, 1.1, 3.3), age 6-12 months (HR 0.3, 95% CI, 0.1, 0.8), and prior neurosurgery (HR 0.4, 95% CI, 0.2, 0.9). After controlling for baseline factors, infection risk was most significantly associated with the need for revision (1 revision vs none, HR 3.9, 95% CI, 2.2, 6.5; ≥2 revisions, HR 13.0, 95% CI, 6.5, 24.9).

CONCLUSIONS

This study quantifies the elevated risk of infection associated with shunt revisions observed in clinical practice. To reduce risk of infection risk, further work should optimize revision procedures.

Pseudomonas aeruginosa phenotypes associated with eradication failure in children with cystic fibrosis

BACKGROUND

Pseudomonas aeruginosa is a key respiratory pathogen in people with cystic fibrosis (CF). Due to its association with lung disease progression, initial detection of P. aeruginosa in CF respiratory cultures usually results in antibiotic treatment with the goal of eradication. Pseudomonas aeruginosa exhibits many different phenotypes in vitro that could serve as useful prognostic markers, but the relative relationships between these phenotypes and failure to eradicate P. aeruginosa have not been well characterized.

METHODS

We measured 22 easily assayed in vitro phenotypes among the baseline P. aeruginosa isolates collected from 194 participants in the 18-month EPIC clinical trial, which assessed outcomes after antibiotic eradication therapy for newly identified P. aeruginosa. We then evaluated the associations between these baseline isolate phenotypes and subsequent outcomes during the trial, including failure to eradicate after antipseudomonal therapy, emergence of mucoidy, and occurrence of an exacerbation.

RESULTS

Baseline P. aeruginosa isolates frequently exhibited phenotypes thought to represent chronic adaptation, including mucoidy. Wrinkly colony surface and irregular colony edges were both associated with increased risk of eradication failure (hazard ratios [95% confidence intervals], 1.99 [1.03-3.83] and 2.14 [1.32-3.47], respectively). Phenotypes reflecting defective quorum sensing were significantly associated with subsequent mucoidy, but no phenotype was significantly associated with subsequent exacerbations during the trial.

CONCLUSIONS

Pseudomonas aeruginosa phenotypes commonly considered to reflect chronic adaptation were observed frequently among isolates at early detection. We found that 2 easily assayed colony phenotypes were associated with failure to eradicate after antipseudomonal therapy, both of which have been previously associated with altered biofilm formation and defective quorum sensing.

Few Patient, Treatment, and Diagnostic or Microbiological Factors, Except Complications and Intermittent Negative Cerebrospinal Fluid (CSF) Cultures During First CSF Shunt Infection, Are Associated With Reinfection

BACKGROUND

The relationship between first and subsequent cerebrospinal fluid (CSF) shunt infections is poorly understood. By understanding the factors associated with increased risk of reinfection, researchers may provide optimal treatment strategies at the time of first infection. The objective of this study was to describe and compare children with and without CSF shunt reinfection.

METHODS

A retrospective cohort study was performed among 118 children who underwent initial CSF shunt placement and developed first CSF shunt infection. The primary outcome variable was CSF shunt reinfection. Patient risk factors and medical and surgical management of initial CSF shunt placement and first CSF shunt infection were compared between children with and without reinfection.

RESULTS

Of 118 children with first infection, 31 (26%) developed a reinfection during the study period (overall median follow-up, 2096 days). Factors associated with reinfection in this cohort included ventriculoatrial or complex shunt at initial CSF shunt placement, complications after first CSF shunt infection, and intermittent negative CSF cultures.

CONCLUSIONS

Few patient or treatment factors were associated with reinfection. Factors associated with difficult-to-treat first CSF shunt infection, including complications after first CSF shunt infection and intermittent negative CSF cultures, were associated with reinfection. Clinicians who treat patients with unusual CSF shunts or more difficult first infections should have a high index of suspicion for reinfection after treatment is completed.

Systematic review of blood biomarkers in cystic fibrosis pulmonary exacerbations

BACKGROUND

Biomarkers reflective of disease activity in cystic fibrosis (CF) have the potential to improve patient care, particularly during CF pulmonary exacerbations (CFPEs). Although blood-based biomarkers have been studied in CFPE for nearly 3 decades, none have been integrated into routine clinical practice. To facilitate progress in this area, we performed a systematic review evaluating blood-based biomarkers during CFPE.

METHODS

MEDLINE, EMBASE, and CENTRAL were searched to identify relevant studies published from January 1995 to August 2012. We included all full-text studies examining systemic (blood-based) biomarkers to aid in the diagnosis of CFPE, predict outcomes of CFPE, and/or monitor the response to CFPE treatment.

RESULTS

Seventy-eight unique blood-based biomarkers have been studied to date, mainly inflammatory cytokines, acute phase reactants, and markers of oxidative stress. C-reactive protein (CRP) consistently correlated with disease activity, with a statistically significant increase from stable to exacerbation state in five of six studies, and changes in response to CFPE treatment, with a statistically significant decrease from the beginning to the end of CFPE treatment in 18 of 20 studies. Other promising biomarkers of CFPE disease activity include neutrophil elastase antiproteinase complex, IL-6, myeloperoxidase (MPO), lactoferrin, and calprotectin.

CONCLUSIONS

Although there are several blood-based biomarkers with evidence for application within the CFPE setting, CRP has been the most widely studied biomarker demonstrating the potential for clinical usefulness. Further validation studies and clinical trials are required to determine whether blood-based biomarkers can be used to ultimately improve health outcomes in the setting of a CFPE.

Evaluation of microbial bacterial and fungal diversity in cerebrospinal fluid shunt infection

Background

Cerebrospinal fluid shunt infection can be recalcitrant. Recurrence is common despite appropriate therapy for the pathogens identified by culture. Improved diagnostic and therapeutic approaches are required, and culture-independent molecular approaches to cerebrospinal fluid shunt infections have not been described.

Objectives

To identify the bacteria and fungi present in cerebrospinal fluid from children with cerebrospinal fluid shunt infection using a high-throughput sequencing approach, and to compare those results to those from negative controls and conventional culture.

Methods

This descriptive study included eight children ≤18 years old undergoing treatment for culture-identified cerebrospinal fluid shunt infection. After routine aerobic culture of each cerebrospinal fluid sample, deoxyribonucleic acid (DNA) extraction was followed by amplification of the bacterial 16S rRNA gene and the fungal ITS DNA region tag-encoded FLX-Titanium amplicon pyrosequencing and microbial phylogenetic analysis.

Results

The microbiota analyses for the initial cerebrospinal fluid samples from all eight infections identified a variety of bacteria and fungi, many of which did not grow in conventional culture. Detection by conventional culture did not predict the relative abundance of an organism by pyrosequencing, but in all cases, at least one bacterial taxon was detected by both conventional culture and pyrosequencing. Individual bacterial species fluctuated in relative abundance but remained above the limits of detection during infection treatment.

Conclusions

Numerous bacterial and fungal organisms were detected in these cerebrospinal fluid shunt infections, even during and after treatment, indicating diverse and recalcitrant shunt microbiota. In evaluating cerebrospinal fluid shunt infection, fungal and anaerobic bacterial cultures should be considered in addition to aerobic bacterial cultures, and culture-independent approaches offer a promising alternative diagnostic approach. More effective treatment of cerebrospinal fluid shunt infections is needed to reduce unacceptably high rates of reinfection, and this work suggests that one effective strategy may be reduction of the diverse microbiota present in infection.

Standard care versus protocol based therapy for new onset Pseudomonas aeruginosa in cystic fibrosis

RATIONALE

The Early Pseudomonal Infection Control (EPIC) randomized trial rigorously evaluated the efficacy of different antibiotic regimens for eradication of newly identified Pseudomonas (Pa) in children with cystic fibrosis (CF). Protocol based therapy in the trial was provided based on culture positivity independent of symptoms. It is unclear whether outcomes observed in the clinical trial were different than those that would have been observed with historical standard of care driven more heavily by respiratory symptoms than culture positivity alone. We hypothesized that the incidence of Pa recurrence and hospitalizations would be significantly reduced among trial participants as compared to historical controls whose standard of care preceded the widespread adoption of tobramycin inhalation solution (TIS) as initial eradication therapy at the time of new isolation of Pa.

METHODS

Eligibility criteria from the trial were used to derive historical controls from the Epidemiologic Study of CF (ESCF) who received standard of care treatment from 1995 to 1998, before widespread availability of TIS. Pa recurrence and hospitalization outcomes were assessed over a 15-month time period.

RESULTS

As compared to 100% of the 304 trial participants, only 296/608 (49%) historical controls received antibiotics within an average of 20 weeks after new onset Pa. Pa recurrence occurred among 104/298 (35%) of the trial participants as compared to 295/549 (54%) of historical controls (19% difference, 95% CI: 12%, 26%, P < 0.001). No significant differences in the incidence of hospitalization were observed between cohorts.

CONCLUSIONS

Protocol-based antimicrobial therapy for newly acquired Pa resulted in a lower rate of Pa recurrence but comparable hospitalization rates as compared to a historical control cohort less aggressively treated with antibiotics for new onset Pa.

Pulmonary exacerbations in CF patients with early lung disease

BACKGROUND

Current definitions of pulmonary exacerbation (PE) in cystic fibrosis are based on studies in participants with significant lung disease and may not reflect the spectrum of findings observed in younger patients with early lung disease.

METHODS

We used data from a recent trial assessing the efficacy of azithromycin in children to study signs and symptoms associated with PEs and related changes in lung function and weight.

RESULTS

While increased cough was present in all PEs, acute weight loss and reduction in oxygen saturation were not observed. Changes in lung function did not differ between subjects who did experience a PE and those who were exacerbation-free.

CONCLUSIONS

Cough was the predominant symptom in CF patients with early lung disease experiencing a PE. There was no significant difference in mean 6-month change in lung function or weight among subjects with one or more exacerbations and those without an exacerbation.

Effect of azithromycin on systemic markers of inflammation in patients with cystic fibrosis uninfected with Pseudomonas aeruginosa

BACKGROUND

While the mechanism of action by which azithromycin exerts positive effects inpatients with cystic fibrosis remains unclear, evidence suggests that azithromycin may act as an immunomodulatory agent. We examined changes in systemic inflammatory markers in a doubleblind, randomized, controlled trial of oral azithromycin in patients 6-18 years of age with cystic fibrosis who were uninfected with Pseudomonas aeruginosa.

METHODS

WBC counts and differential, serum myeloperoxidase (MPO), high-sensitivity C reactive protein (hsCRP), intracellular adhesion molecule 1, IL-6, calprotectin, serum amyloid A (SAA),and granulocyte colony-stimulating factor (G-CSF) were measured at baseline and after 28 and 168 days of treatment in patients receiving either oral azithromycin or placebo.

RESULTS

Inflammatory markers were similar in both groups at baseline. HsCRP, MPO, SAA, calprotectin,and the absolute neutrophil count (ANC) significantly decreased from baseline today 28 in the azithromycin group compared with the placebo group ( P < .05). This treatment effect was sustained at day 168 for ANC, calprotectin, and SAA ( P < .05). Changes in hsCRP, calprotectin,and SAA at day 28 were negatively correlated with changes in FEV 1 (L) and FEV 1(% predicted), as well as both absolute and relative changes in weight ( P < .05). Except for weight (%),the associations remained significant for calprotectin; FEV 1 (L) and weight (%) remained significantly correlated with the 168-day change in hsCRP. The 168-day change in ANC was significantly correlated with changes in lung function, but not in weight; the change in G-CSF was significantly correlated with the change in weight (%) only.

CONCLUSIONS

In patients not infected with P aeruginosa , oral azithromycin significantly reduced neutrophil counts and serum inflammatory markers within 28 days of initiating treatment.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00431964; URL: www.clinicaltrials.gov

Disparities in access to lung transplantation for patients with cystic fibrosis by socioeconomic status

RATIONALE

Although previous studies suggest that access to care for patients with cystic fibrosis (CF) does not vary appreciably by socioeconomic status (SES), disparities with respect to access to lung transplantation for patients with CF are largely unknown.

OBJECTIVES

To determine whether access to lung transplantation for patients with CF differs according to SES.

METHODS

Observational study involving 2,167 adult patients with CF from the CF Foundation Patient registry who underwent their first lung transplant evaluation between 2001 and 2009. The primary outcome was acceptance for lung transplant after initial evaluation. The main SES indicator was Medicaid status. Alternate SES indicators included race, educational attainment, ZIP code-level median household income, and driving time from residence to closest lung transplant center.

MEASUREMENTS AND MAIN RESULTS

The odds that Medicaid recipients were not accepted for lung transplant were 1.56-fold higher (95% confidence interval [CI], 1.27-1.92) than patients without Medicaid, after multivariate adjustment for demographic characteristics, disease severity, and potential contraindications to lung transplant, and before or after use of the lung allocation score. This association was independent of other SES indicators, including race, educational attainment, ZIP code-level median household income, and driving time to closest transplant center (odds ratio [OR] = 1.37; 95% CI, 1.10-1.72). Patients not completing high school (OR = 2.37; 95% CI, 1.49-3.79) and those residing in the lowest (vs. highest) ZIP code median household income category (OR = 1.39; 95% CI, 1.01-1.93) also experienced a higher odds of not being accepted for lung transplant in multivariate analysis.

CONCLUSIONS

In this nationally representative study of adult patients with CF, multiple indicators of low SES were associated with higher odds of not being accepted for lung transplant.

Open-label, follow-on study of azithromycin in pediatric patients with CF uninfected with Pseudomonas aeruginosa

BACKGROUND

We previously performed a randomized placebo-controlled trial to examine the effects of azithromycin in children and adolescents 6-18 years of age with cystic fibrosis uninfected with Pseudomononas aeruginosa and demonstrated that while azithromycin did not acutely improve pulmonary function, azithromycin-reduced pulmonary exacerbations, decreased the initiation of new oral antibiotics, and improved weight gain. We now report the results of the open-label, follow-on study to assess durability of response to azithromycin and continued safety and tolerability.

METHODS

Eligible participants were enrolled in a 24-week open-label study of azithromycin to compare efficacy and safety endpoints during the placebo-controlled trial versus open-label study in two groups: participants initially on azithromycin continued azithromycin (azithromycin-azithromycin) and participants initially on placebo who then received azithromycin (placebo-azithromycin). As in the placebo-controlled trial, the azithromycin dose in the open-label study was 250 mg Monday-Wednesday-Friday for participants weighing 18-35.9 kg and 500 mg Monday-Wednesday-Friday for participants weighing 36 kg or greater.

RESULTS

Of 174 eligible participants, 146 (83.9%) enrolled in the open-label study. No significant improvements in lung function were observed within either group. There were no differences in outcomes in the placebo-azithromycin group during the placebo-controlled versus open-label phase. The azithromycin-azithromycin group had comparable odds of experiencing an exacerbation during the two phases (OR 1.6, CI(95) 0.8, 3.0) and stable weight gain, but new oral antibiotics were initiated more frequently during the open-label study (OR 1.9, CI(95) 1.0, 3.5). In both groups, adverse event rates were comparable during the placebo-controlled and open-label study and treatment-emergent pathogens were rare.

CONCLUSIONS

During the open-label study, we observed continued durability of treatment response to azithromycin, as measured by pulmonary exacerbations and continued weight gain, although use of oral antibiotics increased. There were no new safety concerns. Currently available data suggest that azithromycin reduces exacerbations and improves weight gain for 6-12 months among children and adolescents with CF uninfected with P. aeruginosa.

Risk of post-lung transplant renal dysfunction in adults with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is one of the leading indications for lung transplantation. The incidence and pre-lung transplant risk factors for posttransplant renal dysfunction in the CF population remain undefined.

METHODS

We conducted a cohort study using adults (≥ 18 years old) in the CF Foundation Patient Registry from 2000 to 2008 to determine the incidence of post-lung transplant renal dysfunction, defined by an estimated glomerular filtration rate of < 60 mL/min/1.73 m(2). Multivariable Cox proportional hazards modeling was used to identify independent pretransplant risk factors for post-lung transplant renal dysfunction.

RESULTS

The study cohort included 993 adult lung transplant recipients with CF, with a median follow-up of 2 years. During the study period, 311 individuals developed renal dysfunction, with a 2-year risk of 35% (95% CI, 32%-39%). Risk of posttransplant renal dysfunction increased substantially with increasing age (25 to < 35 years vs 18 to < 25 years: hazard ratio [HR], 1.60; 95% CI, 1.15-2.23; vs ≥ 35 years: HR, 2.45; 95% CI, 1.73-3.47) and female sex (HR, 1.56; 95% CI, 1.22-1.99). CF-related diabetes requiring insulin therapy (HR, 1.30; 95% CI, 1.02-1.67) and pretransplant renal function impairment (estimated glomerular filtration rate, 60-90 mL/min/m(2) vs > 90 mL/min/m(2): HR, 1.58; 95% CI, 1.19-2.12) also increased the risk of posttransplant renal dysfunction.

CONCLUSIONS

Renal dysfunction is common following lung transplant in the adult CF population. Increased age, female sex, CF-related diabetes requiring insulin, and pretransplant renal impairment are significant risk factors.

Initial Pseudomonas aeruginosa treatment failure is associated with exacerbations in cystic fibrosis

RATIONALE

The risk of pulmonary exacerbation following Pseudomonas aeruginosa (Pa) acquisition in children with cystic fibrosis (CF) is unknown.

OBJECTIVES

To determine if failure of antibiotic therapy to eradicate Pa and frequency of Pa recurrence are associated with increased exacerbation risk.

METHODS

The cohort included 282 children with CF who participated in the EPIC trial ages 1-12 with newly acquired Pa, defined as either a first lifetime Pa positive respiratory culture or positive after two years of negative cultures (past isolation of Pa but >2 years prior to the trial). All received antibiotics to promote initial eradication followed by 15 months of intermittent maintenance antibiotics. Quarterly cultures were used to define initial eradication success and subsequent number of Pa recurrences. A standardized symptom-based definition of exacerbation was utilized. Cox proportional hazards models were used to estimate exacerbation risk.

RESULTS

Failure to initially eradicate Pa was associated with exacerbation risk (hazard ratio [HR]: 2.49, 95% confidence interval [CI] 1.26, 4.93). In 245/282 with successful initial eradication during the trial, past isolation of Pa >2 years before the trial was the most significant predictor of exacerbation (HR 1.62, 95% CI 1.12, 2.35). In 37/282 who failed initial eradication, persistent Pa during the maintenance phase (1 or more Pa recurrences after failure to initially eradicate) added even greater exacerbation risk (HR 4.13, 95% CI 1.28, 13.32).

CONCLUSIONS

Children with CF who fail to eradicate after initial antibiotic treatment are at higher risk of subsequent exacerbation, suggesting clinical benefit to successful early eradication of Pa infection.

Association of intraventricular hemorrhage secondary to prematurity with cerebrospinal fluid shunt surgery in the first year following initial shunt placement

OBJECT

The neurosurgical literature has conflicting findings regarding the association between indications for CSF shunt placement and subsequent shunt surgery. The object of this study was to identify baseline factors at the time of initial CSF shunt placement that are independently associated with subsequent surgery.

METHODS

This was a retrospective cohort study of children ages 0-18 years who underwent initial CSF shunt placement between January 1, 1997, and October 12, 2006, at a tertiary care children's hospital. The outcome of interest was CSF shunt surgery (either for revision or infection) within 12 months after initial placement. Associations between subsequent CSF shunt surgery and indication for the initial shunt, adjusting for patient age and surgeon factors at the time of initial placement, were estimated using multivariate logistic regression. Medical and surgical decisions, which varied according to surgeon, were examined separately in a univariate analysis.

RESULTS

Of the 554 children in the study cohort, 233 (42%) underwent subsequent CSF shunt surgery, either for revision (167 patients [30%]) or infection (66 patients [12%]). In multivariate logistic regression modeling, significant risk factors for subsequent CSF shunt surgery included (compared with aqueductal stenosis) intraventricular hemorrhage (IVH) secondary to prematurity (adjusted odds ratio [AOR] 2.2, 95% CI 1.1-4.5) and other unusual indications (AOR 3.7, 95% CI 1.0-13.6). The patient's age at initial CSF shunt placement was not significantly associated with increased odds of subsequent surgery after adjusting for other associated factors.

CONCLUSIONS

The occurrence of IVH is associated with increased odds of subsequent CSF shunt surgery within 12 months after shunt placement. Families of and care providers for children with IVH should be attuned to their increased risk of shunt failure.

Comparative efficacy and safety of 4 randomized regimens to treat early Pseudomonas aeruginosa infection in children with cystic fibrosis

OBJECTIVE

To investigate the efficacy and safety of 4 antipseudomonal treatments in children with cystic fibrosis with recently acquired Pseudomonas aeruginosa infection.

DESIGN

Randomized controlled trial.

SETTING

Multicenter trial in the United States.

PARTICIPANTS

Three hundred four children with cystic fibrosis aged 1 to 12 years within 6 months of P aeruginosa detection.

INTERVENTIONS

Participants were randomized to 1 of 4 antibiotic regimens for 18 months (six 12-week quarters) between December 2004 and June 2009. Participants randomized to cycled therapy received tobramycin inhalation solution (300 mg twice a day) for 28 days, with oral ciprofloxacin (15-20 mg/kg twice a day) or oral placebo for 14 days every quarter, while participants randomized to culture-based therapy received the same treatments only during quarters with positive P aeruginosa cultures.

MAIN OUTCOME MEASURES

The primary end points were time to pulmonary exacerbation requiring intravenous antibiotics and proportion of P aeruginosa -positive cultures.

RESULTS

The intention-to-treat analysis included 304 participants. There was no interaction between treatments. There were no statistically significant differences in exacerbation rates between cycled and culture-based groups (hazard ratio, 0.95; 95% confidence interval [CI], 0.54-1.66) or ciprofloxacin and placebo (hazard ratio, 1.45; 95% CI, 0.82-2.54). The odds ratios of P aeruginosa- positive culture comparing the cycled vs culture-based group were 0.78 (95% CI, 0.49-1.23) and 1.10 (95% CI, 0.71-1.71) comparing ciprofloxacin vs placebo. Adverse events were similar across groups.

CONCLUSIONS

No difference in the rate of exacerbation or prevalence of P aeruginosa positivity was detected between cycled and culture-based therapies. Adding ciprofloxacin produced no benefits.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00097773.

Risk factors for chronic kidney disease in adults with cystic fibrosis

RATIONALE

Adults with cystic fibrosis (CF) possess multiple potential risk factors for chronic kidney disease, including CF-related diabetes (CFRD) and lifetime nephrotoxic drug exposure.

OBJECTIVES

To determine whether cumulative intravenous (IV) aminoglycoside exposure and CFRD increase the risk of chronic kidney disease in adults with CF.

METHODS

This was a cohort study using adults (≥ 18 yr) in the CF Foundation registry from 2001-2008. Chronic kidney disease (stage 3 or greater) was defined by an estimated glomerular filtration rate of less than 60 ml/min/1.73 m(2). Time-dependent multivariable Cox proportional hazards models were used to determine whether cumulative number of acute pulmonary exacerbations (surrogate for IV aminoglycoside exposure) and CFRD requiring insulin increase the risk of chronic kidney disease, adjusting for confounders.

MEASUREMENTS AND MAIN RESULTS

The study cohort included 11,912 adults with a median follow-up of 4 years. During the study period, 204 subjects had chronic kidney disease, with an annual disease prevalence of 2.3%. Disease prevalence doubled with every 10-year increase in age. CFRD requiring insulin therapy substantially increased the risk of chronic kidney disease (1-4 yr of CFRD requiring insulin vs. no CFRD, hazard ratio [HR] = 2.40, 95% confidence interval [CI] 1.74-3.32; ≥ 5 yr, HR = 4.56, 95% CI 2.84-7.31). Pulmonary exacerbations did not significantly increase the risk of chronic kidney disease (one to five exacerbations vs. none, HR = 0.79, 95% CI 0.56-1.11; six to nine exacerbations, HR = 0.92, 95% CI 0.58-1.46; ≥ 10 exacerbations, HR = 1.16, 95% CI 0.75-1.81).

CONCLUSIONS

CF-related diabetes is a significant risk factor for chronic kidney disease in adults with CF, but additional studies examining IV aminoglycoside exposure directly are required.

Using bacterial biomarkers to identify early indicators of cystic fibrosis pulmonary exacerbation onset

Acute periods of pulmonary exacerbation are the single most important cause of morbidity in cystic fibrosis patients, and may be associated with a loss of lung function. Intervening prior to the onset of a substantially increased inflammatory response may limit the associated damage to the airways. While a number of biomarker assays based on inflammatory markers have been developed, providing useful and important measures of disease during these periods, such factors are typically only elevated once the process of exacerbation has been initiated. Identifying biomarkers that can predict the onset of pulmonary exacerbation at an early stage would provide an opportunity to intervene before the establishment of a substantial immune response, with major implications for the advancement of cystic fibrosis care. The precise triggers of pulmonary exacerbation remain to be determined; however, the majority of models relate to the activity of microbes present in the patient's lower airways of cystic fibrosis. Advances in diagnostic microbiology now allow for the examination of these complex systems at a level likely to identify factors on which biomarker assays can be based. In this article, we discuss key considerations in the design and testing of assays that could predict pulmonary exacerbations.

Effect of VX-770 in persons with cystic fibrosis and the G551D-CFTR mutation

BACKGROUND

A new approach in the treatment of cystic fibrosis involves improving the function of mutant cystic fibrosis transmembrane conductance regulator (CFTR). VX-770, a CFTR potentiator, has been shown to increase the activity of wild-type and defective cell-surface CFTR in vitro.

METHODS

We randomly assigned 39 adults with cystic fibrosis and at least one G551D-CFTR allele to receive oral VX-770 every 12 hours at a dose of 25, 75, or 150 mg or placebo for 14 days (in part 1 of the study) or VX-770 every 12 hours at a dose of 150 or 250 mg or placebo for 28 days (in part 2 of the study).

RESULTS

At day 28, in the group of subjects who received 150 mg of VX-770, the median change in the nasal potential difference (in response to the administration of a chloride-free isoproterenol solution) from baseline was -3.5 mV (range, -8.3 to 0.5; P=0.02 for the within-subject comparison, P=0.13 vs. placebo), and the median change in the level of sweat chloride was -59.5 mmol per liter (range, -66.0 to -19.0; P=0.008 within-subject, P=0.02 vs. placebo). The median change from baseline in the percent of predicted forced expiratory volume in 1 second was 8.7% (range, 2.3 to 31.3; P=0.008 for the within-subject comparison, P=0.56 vs. placebo). None of the subjects withdrew from the study. Six severe adverse events occurred in two subjects (diffuse macular rash in one subject and five incidents of elevated blood and urine glucose levels in one subject with diabetes). All severe adverse events resolved without the discontinuation of VX-770.

CONCLUSIONS

This study to evaluate the safety and adverse-event profile of VX-770 showed that VX-770 was associated with within-subject improvements in CFTR and lung function. These findings provide support for further studies of pharmacologic potentiation of CFTR as a means to treat cystic fibrosis. (Funded by Vertex Pharmaceuticals and others; ClinicalTrials.gov number, NCT00457821.).

An international randomized multicenter comparison of nasal potential difference techniques

BACKGROUND

The transepithelial nasal potential difference (NPD) is used to assess cystic fibrosis transmembrane conductance regulator (CFTR) activity. Unreliability, excessive artifacts, and lack of standardization of current testing systems can compromise its use as a diagnostic test and outcome measure for clinical trials.

METHODS

To determine whether a nonperfusing (agar gel) nasal catheter for NPD measurement is more reliable and less susceptible to artifacts than a continuously perfusing nasal catheter, we performed a multicenter, randomized, crossover trial comparing a standardized NPD protocol using an agar nasal catheter with the same protocol using a continuously perfusing catheter. The data capture technique was identical in both protocols. A total of 26 normal adult subjects underwent NPD testing at six different centers.

RESULTS

Artifact frequency was reduced by 75% (P < .001), and duration was less pronounced using the agar catheter. The measurement of sodium conductance was similar between the two catheter methods, but the agar catheter demonstrated significantly greater CFTR-dependent hyperpolarization, because Δ zero Cl- + isoproterenol measurements were significantly more hyperpolarized with the agar catheter (224.2 ± 12.9 mV with agar vs 18.2 ± 9.1 mV with perfusion, P < .05).

CONCLUSIONS

The agar nasal catheter approach demonstrates superior reliability compared with the perfusion nasal catheter method for measurement of NPD. This nonperfusion catheter method should be considered for adoption as a standardized protocol to monitor CFTR activity in clinical trials.

Effect of azithromycin on pulmonary function in patients with cystic fibrosis uninfected with Pseudomonas aeruginosa: a randomized controlled trial

CONTEXT

Azithromycin is recommended as therapy for cystic fibrosis (CF) patients with chronic Pseudomonas aeruginosa infection, but there has not been sufficient evidence to support the benefit of azithromycin in other patients with CF.

OBJECTIVE

To determine if azithromycin treatment improves lung function and reduces pulmonary exacerbations in pediatric CF patients uninfected with P. aeruginosa.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter, randomized, double-blind placebo-controlled trial was conducted from February 2007 to July 2009 at 40 CF care centers in the United States and Canada. Of the 324 participants screened, 260 were randomized and received study drug. Eligibility criteria included age of 6 to 18 years, a forced expiratory volume in the first second of expiration (FEV(1)) of at least 50% predicted, and negative respiratory tract cultures for P. aeruginosa for at least 1 year. Randomization was stratified by age of 6 to 12 years vs 13 to 18 years and by CF center.

INTERVENTION

The active group (n = 131) received 250 mg (weight 18-35.9 kg) or 500 mg (weight > or = 36 kg) of azithromycin 3 days per week (Monday, Wednesday, and Friday) for 168 days. The placebo group (n = 129) received identically packaged placebo tablets on the same schedule.

MAIN OUTCOME MEASURES

The primary outcome was change in FEV(1). Exploratory outcomes included additional pulmonary function end points, pulmonary exacerbations, changes in weight and height, new use of antibiotics, and hospitalizations. Changes in microbiology and adverse events were monitored.

RESULTS

The mean (SD) age of participants was 10.7 (3.17) years. The mean (SD) FEV(1) at baseline and 168 days were 2.13 (0.85) L and 2.22 (0.86) L for the azithromycin group and 2.12 (0.85) L and 2.20 (0.88) L for the placebo group. The difference in the change in FEV(1) between the azithromycin and placebo groups was 0.02 L (95% confidence interval [CI], -0.05 to 0.08; P = .61). None of the exploratory pulmonary function end points were statistically significant. Pulmonary exacerbations occurred in 21% of the azithromycin group and 39% of the placebo group. Participants in the azithromycin group had a 50% reduction in exacerbations (95% CI, 31%-79%) and an increase in body weight of 0.58 kg (95% CI, 0.14-1.02) compared with placebo participants. There were no significant differences between groups in height, use of intravenous or inhaled antibiotics, or hospitalizations. Participants in the azithromycin group had no increased risk of adverse events, but had less cough (-23% treatment difference; 95% CI, -33% to -11%) and less productive cough (-11% treatment difference; 95% CI, -19% to -3%) compared with placebo participants.

CONCLUSION

In children and adolescents with CF uninfected with P. aeruginosa, treatment with azithromycin for 24 weeks did not result in improved pulmonary function.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00431964.

Early anti-pseudomonal acquisition in young patients with cystic fibrosis: rationale and design of the EPIC clinical trial and observational study'

BACKGROUND

The primary cause of morbidity and mortality in patients with cystic fibrosis (CF) is progressive obstructive pulmonary disease due to chronic endobronchial infection, particularly with Pseudomonas aeruginosa (Pa). Risk factors for and clinical impact of early Pa infection in young CF patients are less well understood.

PURPOSE

The present studies are designed to evaluate risk factors and outcomes associated with early Pa acquisition, and the benefits and harms of four anti-pseudomonal treatment regimens in young CF patients initiated after the first Pa positive respiratory culture.

METHODS

The Early Pseudomonas Infection Control (EPIC) program consists of two studies, a randomized multicenter trial in CF patients ages 1-12 years at first isolation of Pa from a respiratory culture, and a longitudinal cohort study enrolling Pa-negative patients. Using a factorial design, trial participants are assigned for 18 months to either anti-pseudomonal treatment on a scheduled quarterly basis (cycled therapy) or based on recovery of Pa from quarterly respiratory cultures (culture-based therapy). The study drugs include inhaled tobramycin (300 mg BID) for 28 days, combined with either oral ciprofloxacin (15-20 mg/kg BID) or oral placebo for 14 days. The primary endpoints of the trial are the time to pulmonary exacerbation requiring IV antibiotics or hospitalization for respiratory symptoms, and the proportion of patients with new Pa-positive respiratory cultures during the study. The broad goals of the observational study are to describe the risk factors and outcomes associated with early acquisition of Pa. 306 patients were randomized in the clinical trial and 1787 were enrolled in the cohort study.

CONCLUSIONS

These companion studies will provide valuable epidemiological and microbiological information on early CF lung disease and Pa acquisition, and safety and clinical efficacy data on anti-pseudomonal treatment strategies for early Pa infections in the airways of young children with CF.

Reproducibility of spirometry during cystic fibrosis pulmonary exacerbations

OBJECTIVES

To compare the within day variation of spirometry between hospital admission, discharge, and outpatient follow up among children with cystic fibrosis (CF) hospitalized for a pulmonary exacerbation.

HYPOTHESIS

Within day variation of spirometry will be greater at hospital admission than at hospital discharge or outpatient follow up.

METHODS

We performed a retrospective review of spirometry data for all patients with CF >or=6 years old admitted to our pediatric CF center for a pulmonary exacerbation in 2004 or 2005. For patients who had previously performed spirometry successfully, measurements were used from one admission only during 2004-2005 if the spirometry occurred within 3 days of hospital admission, 3 days of discharge, or at a follow up clinic visit when well. We compared the within day coefficients of variation (CV) for FVC, FEV(1), and FEF(25-75) between time points using the Wilcoxon signed rank-test. We also determined the change in spirometry that is likely to be beyond measurement variability during inpatient treatment of a pulmonary exacerbation.

RESULTS

Spirometry data were available from 40 subjects at admission and follow up and 35 at hospital discharge. There was no significant difference in CV at admission, discharge, and follow up for FVC, FEV(1), or FEF(25-75). The mean (SD) CV was 3.1% (2.7) for FVC, 3.2% (2.1) for FEV(1), and 9.7% (7.0) for FEF(25-75) at admission, 2.8% (2.2) for FVC, 3.1% (2.1) for FEV(1), and 8.1% (6.7) for FEF(25-75) at discharge, and 2.7% (1.7) for FVC, 2.8% (2.0) for FEV(1), and 8.4% (7.8) for FEF(25-75) at follow up. These are similar to previous reports of outpatients with CF. The improvement in spirometry that exceeded measurement variability for our cohort was 80 ml for FVC, 70 ml for FEV(1), and 220 ml/sec for FEF(25-75).

CONCLUSIONS

The presence of an acute pulmonary exacerbation in children and adolescents with CF does not substantially contribute to the within day variation in spirometry. Within day variation of spirometry for children with CF during pulmonary exacerbations is similar to previously reported values from clinically stable CF patients.

Shifting patterns of inhaled antibiotic use in cystic fibrosis

RATIONALE

Antibiotic inhalation has become widely accepted as a standard treatment for cystic fibrosis (CF) airway infection. We assessed the prevalence and context of inhaled antibiotic use in the North American CF population. Our working hypothesis was that a shift from acute to chronic use of inhaled antibiotics has coincided with increased prevalence of use among CF patients.

METHODS

Descriptive statistics were collected for 30,833 patients enrolled in the Epidemiologic Study of CF (ESCF) during 1996 through 2005. A multivariate analysis was performed on data from a subgroup of 18,021 patients enrolled in ESCF during 2003 through 2005.

RESULTS

The prevalence of inhaled antibiotic use in the North American CF population increased during 1996 through 2005 due to increased chronic use, while acute use to treat pulmonary exacerbations decreased. In 2005, 50% of CF patients used inhaled tobramycin and 9% used inhaled colistin chronically; most of the latter used both agents concurrently. Airway obstruction severity and airway infection status were predictors of inhaled antibiotic use.

CONCLUSIONS

Increased chronic use and decreased acute use of inhaled antibiotics presumably reflect a shift toward more proactive management of airway infections in the North American CF population. The effects of these usage patterns on long-term clinical outcomes and emergence of antibiotic-resistant Pseudomonas aeruginosa strains warrant further study.

Advancing outcome measures for the new era of drug development in cystic fibrosis

The growing pipeline of candidate drugs for cystic fibrosis (CF) is challenging clinical trial research. There has been a shift from evaluating drugs aimed at treating the secondary manifestations of CF to evaluating drugs targeted toward the primary prevention of chronic lung disease. As CF is an orphan disease, there is a fundamental need to assess new therapies efficiently and accurately by mechanisms that best use the number of available patients. This need can be addressed with the continued advancement and refinement of CF outcome measures. We begin by presenting an overview of the outcome measures currently used in CF clinical studies, defined and categorized in terms of one of the three main classes of endpoints: clinical efficacy measures, surrogate endpoints, and biomarkers. To move forward efficiently, clinical research in CF is dependent on the development of new outcomes able to capture biologic and clinical response to novel therapeutic approaches. We conclude with a discussion of the criteria by which all new outcome measures should be evaluated. A systematic, rigorous approach to outcome measure development is needed to provide the tools necessary for evaluating new therapies and moving drugs out of the pipeline and into the CF clinic.

Duration of treatment effect after tobramycin solution for inhalation in young children with cystic fibrosis

RATIONALE

Among young children with cystic fibrosis (CF), Pseudomonas aeruginosa (Pa) airway infection is associated with increased morbidity and mortality. Early intervention strategies include tobramycin solution for inhalation (TSI), which can eradicate lower airway Pa from cultures obtained at the end of 28 days of treatment in young children.

METHODS

We conducted an open label, sequential cohort study of TSI in young children with CF to investigate duration of antimicrobial treatment effect. The primary outcome was lower airway Pa eradication per bronchoalveolar lavage (BAL) fluid culture. Sequential treatment cohorts varied by duration of treatment (28 or 56 days) and timing of follow-up BAL (at Days 56, 84, or 112). Subjects (N = 36) were treated with TSI, 300 mg twice daily, for 28 days or 56 days per cohort assignment.

RESULTS

Among 31 evaluable subjects, culture based, lower airway Pa eradication was observed in the majority of subjects for up to 1-3 months following TSI treatment: 75% in Cohort 28/56 (days of treatment/day of follow-up BAL), 63% in Cohort 28/84, 82% in Cohort 56/112, and 75% in Cohort 28/112. Non-mucoid Pa at baseline and/or exotoxin A seronegativity were associated with higher rates of eradication. There was a less pronounced effect of TSI treatment on Pa eradication from oropharyngeal cultures in all cohorts. TSI treatment was associated with reduced neutrophilic airway inflammation and was not related to any serious adverse events.

CONCLUSION

TSI monotherapy is safe and can eradicate lower airway Pa for up to 3 months after treatment in young children with CF.

Clinical response to azithromycin in cystic fibrosis correlates with in vitro effects on Pseudomonas aeruginosa phenotypes

A 6-month clinical trial of azithromycin (AZM) in American cystic fibrosis (CF) patients with chronic Pseudomonas aeruginosa infection showed clinical improvement without significant reduction in bacterial density. Sub-inhibitory AZM has been hypothesized to affect P. aeruginosa virulence, partly contributing to the mechanism of action of AZM. To correlate bacterial phenotypes of P. aeruginosa isolates with clinical response to AZM in CF patients. Pre-treatment P. aeruginosa isolates from subjects randomized to AZM in the US trial were characterized for bacterial phenotypes: AZM minimal inhibitory concentration (MIC), mucoidy, and baseline and AZM effects on twitching and swimming motility, and production of pyocyanin, protease and phospholipase C (PLC). Initial analyses of a subset of subjects identified phenotypes most strongly associated with FEV(1) response and pulmonary exacerbation. These phenotypes were subsequently characterized and tested in isolates from subjects of the complete AZM cohort. Exploratory analyses of the initial subset suggested that the MIC and in vitro change in PLC and swimming motility with AZM were the strongest candidates among the bacterial phenotypes. When tested, only the change in PLC was significantly correlated with the change in FEV(1) (P=0.05), and occurrence and time to pulmonary exacerbation (both P=0.02). In the complete cohort, change in PLC continued to show significant correlation with FEV(1) response (P=0.006), but not exacerbation. The in vitro effect of AZM on PLC correlates with FEV(1) response to AZM. This suggests that AZM anti-virulence effects may be predictive of clinical response and play a role in the mechanism of action of AZM in CF patients.

No detectable improvements in cystic fibrosis transmembrane conductance regulator by nasal aminoglycosides in patients with cystic fibrosis with stop mutations

Cystic fibrosis (CF) is an autosomal recessive disorder caused by many types of genetic defects, including premature stop codons. Gentamicin can suppress stop mutations in CF transmembrane conductance regulator (CFTR) in vitro and in vivo, leading to improvements in CFTR-dependent ion transport and protein localization to the apical surface of respiratory epithelial cells. The primary objective of this study was to test whether nasally administered gentamicin or tobramycin could suppress premature stop mutations in CFTR, resulting in full-length, functional protein. A secondary objective was to obtain data to aid in the design of multicenter trials using the nasal potential difference as a study endpoint. A multicenter study was conducted in two cohorts of patients with CF, those heterozygous for stop mutations in the CFTR gene and those without nonsense mutations, to investigate the effects of both gentamicin and tobramycin administered over a 28-d period on sequential nasal potential difference and airway cell immunofluorescence endpoints. Eleven patients with CF with stop mutations were enrolled in a randomized, double-blinded, crossover fashion to receive each drug, while 18 subjects with CF without stop mutations were randomized 1:1 in a parallel fashion to receive one drug. After demonstration of drug delivery, neither aminoglycoside produced detectable changes in nasal ion transport or CFTR localization in brushed cells from either study group. These results with first-generation suppressive agents suggest the need for improved drug delivery methods and/or more potent suppressors of nonsense mutations to confer CFTR correction in subjects with CF heterozygous for nonsense mutations. The study provides valuable information on parameters of the nasal potential difference measurements for use in future multicenter clinical trials.