Evolution of lung function during the first year of life in newborn screened cystic fibrosis infants

Accurate lung volume measurements in vitro using a novel inert gas washout method suitable for infants

BACKGROUND

Multiple breath washout (MBW) in infants presents a number of technical challenges. Conventional MBW is based on simultaneous measurement of flow and gas concentrations. These two signals are aligned and combined to derive expired gas volumes from which lung volumes and measures of ventilation inhomogeneity are calculated. Accuracy of measurement becomes increasingly vulnerable to errors in gas signal alignment at fast respiratory rates. In this paper we describe an alternative method of performing MBW in infants. Expired gas is collected and analyzed to derive functional residual capacity (FRC) and lung clearance index (LCI). This eliminates the need for simultaneous measurement of flow, and integration of flow and gas signals, and significantly reduces deadspace.

METHODS

A highly accurate lung model incorporating BTPS conditions was used to generate realistic infant breathing parameters: FRC of 100-250 mls with respiratory rate of 20-60 min(-1) . In vitro accuracy of FRC measurement using the novel MBW method was assessed using the model.

RESULTS

Overall mean error (standard deviation) of FRC measurement was -1.0 (3.3)% with 90% of tests falling within ±5%.

DISCUSSION

FRC measurement using the novel method has superior accuracy in vitro than previously described systems. By uncoupling the measurement of gas volumes from real-time flow and gas measurement, this system offers an alternative method of MBW which is well suited to infants.

Clinical Practice Guidelines From the Cystic Fibrosis Foundation for Preschoolers With Cystic Fibrosis

Cystic fibrosis (CF) clinical care guidelines exist for the care of infants up to age 2 years and for individuals ≥6 years of age. An important gap exists for preschool children between the ages of 2 and 5 years. This period marks a time of growth and development that is critical to achieve optimal nutritional status and maintain lung health. Given that disease often progresses in a clinically silent manner, objective and sensitive tools that detect and track early disease are important in this age group. Several challenges exist that may impede the delivery of care for these children, including adherence to therapies. A multidisciplinary committee was convened by the CF Foundation to develop comprehensive evidence-based and consensus recommendations for the care of preschool children, ages 2 to 5 years, with CF. This document includes recommendations in the following areas: routine surveillance for pulmonary disease, therapeutics, and nutritional and gastrointestinal care.

Multiple-Breath Washout as a Lung Function Test in Cystic Fibrosis. A Cystic Fibrosis Foundation Workshop Report

The lung clearance index (LCI) is a lung function parameter derived from the multiple-breath washout (MBW) test. Although first developed 60 years ago, the technique was not widely used for many years. Recent technological advances in equipment design have produced gains in popularity for this test among cystic fibrosis (CF) researchers and clinicians, particularly for testing preschool-aged children. LCI has been shown to be feasible and sensitive to early CF lung disease in patients of all ages from infancy to adulthood. A workshop was convened in January 2014 by the North American Cystic Fibrosis Foundation to determine the readiness of the LCI for use in multicenter clinical trials as well as clinical care. The workshop concluded that the MBW text is a valuable potential outcome measure for CF clinical trials in preschool-aged patients and in older patients with FEV1 in the normal range. However, gaps in knowledge about the choice of device, gas, and standardization across systems are key issues precluding its use as a clinical trial end point in infants. Based on the current evidence, there are insufficient data to support the use of LCI or MBW parameters in the routine clinical management of patients with CF.

Safety, pharmacokinetics, and pharmacodynamics of ivacaftor in patients aged 2-5 years with cystic fibrosis and a CFTR gating mutation (KIWI): an open-label, single-arm study

BACKGROUND

Ivacaftor has been shown to be a safe, effective treatment for cystic fibrosis in patients aged 6 years or older with a CFTR gating mutation. We aimed to assess the safety, pharmacokinetics, and pharmacodynamics of ivacaftor in children aged 2-5 years.

METHODS

In the two-part KIWI study, we enrolled children aged 2-5 years weighing 8 kg or more with a confirmed diagnosis of cystic fibrosis and a CFTR gating mutation on at least one allele from 15 hospitals in the USA, UK, and Canada. Participants received oral ivacaftor 50 mg (if bodyweight <14 kg) or 75 mg (if bodyweight ≥14 kg) every 12 h for 4 days in part A (to establish the short-term safety of doses for subsequent assessment in part B), and then for 24 weeks in part B (to assess safety and longer-term pharmacodynamics). Children could participate in both or just one part of the study. Primary outcomes were pharmacokinetics and safety, analysed in all patients who received at least one dose of ivacaftor. Secondary outcomes were absolute change from baseline in sweat chloride concentrations and bodyweight, body-mass index (BMI), and height Z scores, and pharmacokinetic parameter estimation of ivacaftor. This study is registered with ClinicalTrials.gov, number NCT01705145.

FINDINGS

Between Jan 8, 2013, and March 1, 2013, nine patients were enrolled onto part A of the study, all of whom completed the 4 day treatment period, and eight of whom took part in part B. Between June 28, 2013, and Sept 26, 2013, 34 patients were enrolled in part B, 33 of whom completed the 24 week treatment period. All patients received at least one dose of ivacaftor. Results of ivacaftor pharmacokinetics suggested that exposure was similar to that reported in adults (median Cmin were 536 ng/mL for the 50 mg dose; 580 ng/mL for the 75 mg dose; median ivacaftor AUC values were 9840 ng × h/mL and 10 200 ng × h/mL, respectively). Common adverse events in part B included cough (in 19 [56%] of 34 patients) and vomiting (in ten [29%]). Five (15%) patients had liver function test (LFT) results that were more than eight times higher than the upper limit of normal, four of whom had study drug interrupted, and one of whom had study drug discontinued. Six (18%) of 34 patients had seven serious adverse events; a raised concentration of transaminases was the only serious adverse event regarded as related to ivacaftor and the only adverse event that resulted in study treatment discontinuation. At week 24, in patients for whom we had data, sweat chloride had changed from baseline by a mean of -46·9 mmol/L (SD 26·2, p<0·0001), weight Z score by 0·2 (0·3; p<0·0001), BMI Z score by 0·4 (0·4, p<0·0001), and height Z score by -0·01 (0·3; p=0·84).

INTERPRETATION

Ivacaftor at doses of 50 mg and 75 mg seems to be safe in children aged 2-5 years with cystic fibrosis with a gating mutation followed up for 24 weeks, although the frequency of elevated LFTs suggests that monitoring should be frequent in young children, particularly those with a history of elevated LFTs. Results of an ongoing extension study assessing durability of these effects and longer-term safety are warranted.

FUNDING

Vertex Pharmaceuticals Incorporated.

Infant lung function tests as endpoints in the ISIS multicenter clinical trial in cystic fibrosis

BACKGROUND

The Infant Study of Inhaled Saline (ISIS) in CF was the first multicenter clinical trial to utilize infant pulmonary function tests (iPFTs) as an endpoint.

METHODS

Secondary analysis of ISIS data was conducted in order to assess feasibility of iPFT measures and their associations with respiratory symptoms. Standard deviations were calculated to aid in power calculations for future clinical trials.

RESULTS

Seventy-three participants enrolled, 70 returned for the final visit; 62 (89%) and 45 (64%) had acceptable paired functional residual capacity (FRC) and raised volume measurements, respectively. Mean baseline FEV0.5, FEF75 and FRC z-scores were 0.3 (SD: 1.2), -0.2 (SD: 2.0), and 1.8 (SD: 2.0).

CONCLUSIONS

iPFTs are not appropriate primary endpoints for multicenter clinical trials due to challenges of obtaining acceptable data and near-normal average raised volume measurements. Raised volume measures have potential to serve as secondary endpoints in future clinical CF trials.

2014 year in review: Cystic fibrosis

In this article, we highlight cystic fibrosis (CF) research published in Pediatric Pulmonology during 2014, as well as related articles published in other journals.

Cystic Fibrosis Papers of the Year, 2013-2014

Studies published in the last year in the field of cystic fibrosis have provided more data on the safety and efficacy of a number of therapies, including mutation-specific drugs. There have also been a number of publications on monitoring of early lung disease including the use of lung clearance index and magnetic resonance scanning. Evidence suggests early lung changes may remain relatively static over the first year of life. There are important outcome differences across national patient registries and there is also the increasing recognition of psychological illnesses and possible drug interactions as treatment becomes more complicated and survival improves.

Highlights of the 28(th) North American Cystic Fibrosis Conference 2014

This is a selection of papers presented at the 28(th) North American Cystic Fibrosis Conference held in Atlanta in October 2014. The papers discussed are thought to be of particular interest to CF caregivers in the UK. Topics discussed include recent progress in the modification of the cystic fibrosis transmembrane regulator (CFTR), the potential of OligoG, a novel inhaled alginate mucolytic, and the changing approach to cystic fibrosis-related diabetes screening.

Induced sputum in young healthy children with cystic fibrosis

Young children with CF are often asymptomatic and non-productive, yet CF lung disease occurs early in life. Cough swabs are used routinely to sample bacteria from the CF respiratory tract in non-productive healthy children; bronchoscopy is used to definitively sample the lower airway, but is an invasive procedure. Induced sputum is a non-invasive approach to sampling the lower airway. The article concentrates on how well it is tolerated in children, how successful it is in identifying respiratory pathogens, and how it may be important in routine surveillance if 16S technology is to be used in the clinical forum.

Infant pulmonary function testing in chronic pneumonitis of infancy due to surfactant protein C mutation

Pulmonary function testing is a vital tool in evaluation and management of adult ILD patients and is rarely overlooked during workup. However, there is paucity of data regarding its usefulness in management of infants with suspected interstitial lung disease. In this paper, we present the contribution of infant pulmonary function testing (iPFT) to the management of two infants with biopsy confirmed chronic pneumonitis of infancy due to surfactant protein C mutation. We have productively and safely used serial iPFT for decision making both during diagnosis and follow-up of these infants.

Cystic fibrosis

Cystic fibrosis is an autosomal recessive, monogenetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. The gene defect was first described 25 years ago and much progress has been made since then in our understanding of how CFTR mutations cause disease and how this can be addressed therapeutically. CFTR is a transmembrane protein that transports ions across the surface of epithelial cells. CFTR dysfunction affects many organs; however, lung disease is responsible for the vast majority of morbidity and mortality in patients with cystic fibrosis. Prenatal diagnostics, newborn screening and new treatment algorithms are changing the incidence and the prevalence of the disease. Until recently, the standard of care in cystic fibrosis treatment focused on preventing and treating complications of the disease; now, novel treatment strategies directly targeting the ion channel abnormality are becoming available and it will be important to evaluate how these treatments affect disease progression and the quality of life of patients. In this Primer, we summarize the current knowledge, and provide an outlook on how cystic fibrosis clinical care and research will be affected by new knowledge and therapeutic options in the near future. For an illustrated summary of this Primer, visit: http://go.nature.com/4VrefN.

Birth data accessibility via primary care health records to classify health status in a multi-ethnic population of children: an observational study

Background:

Access to reliable birth data (birthweight (BW) and gestational age (GA)) is essential for the identification of individuals who are at subsequent health risk.

Aims:

This study aimed to explore the feasibility of retrospectively collecting birth data for schoolchildren from parental questionnaires (PQ) and general practitioners (GPs) in primary care clinics, in inner city neighbourhoods with high density of ethnic minority and disadvantaged populations.

Methods:

Attempts were made to obtain birth data from parents and GPs for 2,171 London primary schoolchildren (34% White, 29% Black African origin, 25% South Asians, 12% Other) as part of a larger study of respiratory health.

Results:

Information on BW and/or GA were obtained from parents for 2,052 (95%) children. Almost all parents (2,045) gave consent to access their children’s health records held by GPs. On the basis of parental information, GPs of 1,785 children were successfully contacted, and GPs of 1,202 children responded. Birth data were retrieved for only 482 children (22% of 2,052). Missing birth data from GPs were associated with non-white ethnicity, non-UK born, English not the dominant language at home or socioeconomic disadvantage. Paired data were available in 376 children for BW and in 407 children for GA. No significant difference in BW or GA was observed between PQ and GP data, with <5% difference between sources regardless of normal or low birth weight, or term or preterm status.

Conclusions:

Parental recall of birth data for primary schoolchildren yields high quality and rapid return of data, and it should be considered as a viable alternative in which there is limited access to birth records. It provides the potential to include children with an increased risk of health problems within epidemiological studies.

How to avoid misinterpreting lung function tests in children: a few practical tips

Assessments of pulmonary function play an integral part in the clinical management of school age children as well as providing objective outcome measures in clinical and epidemiological research studies. Pulmonary function tests (PFTs) can also be undertaken in sleeping infants and in awake young children from 3 years of age. However, the clinical utility of such assessments, which are generally confined to specialist centres, has yet to be established. Whether requesting or undertaking paediatric PFTs, or simply reading about how these tests have been applied in research studies, it is essential to question whether results have been interpreted in a meaningful way. This review summarises some of the issues that need to be considered, including: why the tests are being performed; which tests are most likely to detect the suspected pathophysiology; how often such tests should be repeated; whether results are likely to be reliable (in terms of data quality, repeatability and the availability of suitable reference equations with which to distinguish the effects of disease from those of growth and development), and whether the selected tests are likely to be feasible in the individual child or study group under investigation.

Is chest CT useful in newborn screened infants with cystic fibrosis at 1 year of age?

Rationale

Sensitive outcome measures applicable in different centres to quantify and track early pulmonary abnormalities in infants with cystic fibrosis (CF) are needed both for clinical care and interventional trials. Chest CT has been advocated as such a measure yet there is no validated scoring system in infants.

Objectives

The objectives of this study were to standardise CT data collection across multiple sites; ascertain the incidence of bronchial dilatation and air trapping in newborn screened (NBS) infants with CF at 1 year; and assess the reproducibility of Brody-II, the most widely used scoring system in children with CF, during infancy.

Methods

A multicentre observational study of early pulmonary lung disease in NBS infants with CF at age 1 year using volume-controlled chest CT performed under general anaesthetic.

Main results

65 infants with NBS-diagnosed CF had chest CT in three centres. Small insignificant variations in lung recruitment manoeuvres but significant centre differences in radiation exposures were found. Despite experienced scorers and prior training, with the exception of air trapping, inter- and intraobserver agreement on Brody-II score was poor to fair (eg, interobserver total score mean (95% CI) κ coefficient: 0.34 (0.20 to 0.49)). Only 7 (11%) infants had a total CT score ≥12 (ie, ≥5% maximum possible) by either scorer.

Conclusions

In NBS infants with CF, CT changes were very mild at 1 year, and assessment of air trapping was the only reproducible outcome. CT is thus of questionable value in infants of this age, unless an improved scoring system for use in mild CF disease can be developed.