The impact of switching to the new global lung function initiative equations on spirometry results in the UK CF registry

Referential equations for pulmonary diffusing capacity generated from the Japanese population using the Lambda, Mu, or Sigma method and their comparisons with prior referential equations

BACKGROUND

This study aimed to establish reference equations for single-breath lung carbon monoxide diffusing capacity (DLCO), alveolar volume (VA), and transfer coefficient of the lungs for carbon monoxide (KCO, sometimes written as DLCO/VA) in the Japanese population. A generalised additive model for location size and shape (GAMLSS) was used to build each equation.

METHODS

To collect pulmonary function data throughout a broad age range, we prospectively obtained pulmonary function data from healthy volunteers and retrospectively obtained data from patients with normal diffusing capacity aged 16-85 years.

RESULTS

In total, 702 tests were conducted. The validation group z-scores, except for DLCO in males, showed substantial discrepancies between the Global Lung Initiative (GLI) baseline prediction equations and the present study's prediction equations, indicating the need for a new reference value prediction approach. The root mean square errors of the DLCO, VA, and KCO reference values obtained from the present study's prediction equations were lower than those derived from the GLI and previous linear regression equations.

CONCLUSIONS

Reference values obtained in this study were more appropriate for our sample than those derived from the existing baseline prediction equations. This research's contribution is the development of a more precise prediction equation that can be used to establish a reference value range for pulmonary diffusing capacity.

ETHICS AND DISSEMINATION

This research does not include any dissemination plan (publications, data deposition and curation).

Association of Oxygen Therapy with the Natural Disease Progression of Cystic Fibrosis: A Multi-State Model of the European Cystic Fibrosis Society Patient Registry

Background

Association between dependence on oxygen therapy (OT) and natural disease progression in people with cystic fibrosis (pwCF) has not been estimated yet. The aim of this study is to understand the prognosis for pwCF on OT, evaluating how the transition probabilities from being alive without lung transplantation (LTx) to LTx and to death, and from being alive after LTx to death change in pwCF with and without OT.

Methods

We used 2008-2017 data from the 35-country European CF Society Patient Registry. A multi-state model was fitted to assess the effects of individual risk factors on transition probabilities.

Results

We considered 48,343 pwCF aged from 6 to 50 years. OT (HR 5.78, 95% CI: 5.32-6.29) and abnormal FEV₁ (HR 6.41, 95% CI: 5.28-7.79) were strongly associated with the probability of having LTx; chronic infection with Burkholderia cepacia complex (HR 3.19, 95% CI: 2.78-3.67), abnormal FEV₁ (HR 5.00, 95% CI: 4.11-6.08) and the need for OT (HR 4.32, 95% CI: 3.93-4.76) showed the greatest association with the probability of dying without LTx. Once pwCF received LTx, OT (HR 1.75, 95% CI: 1.41-2.16) and abnormal FEV₁ (HR 1.63, 95% CI: 1.18-2.25) were the main factors associated with the probability of dying. An association of gross national income with the probability of receiving LTx and with the probability of dying without LTx was also found.

Conclusion

Oxygen therapy is associated with poor survival in pwCF with and without LTx; harmonization of CF care throughout European countries and minimization of the onset of pulmonary gas exchange abnormalities using all available means remains of paramount importance.

Lower airway clinical outcome measures for use in primary ciliary dyskinesia research: a scoping review

OBJECTIVES

Disease-specific, well-defined and validated clinical outcome measures are essential in designing research studies. Poorly defined outcome measures hamper pooling of data and comparisons between studies. We aimed to identify and describe pulmonary outcome measures that could be used for follow-up of patients with primary ciliary dyskinesia (PCD).

METHODS

We conducted a scoping review by systematically searching MEDLINE, Embase and the Cochrane Database of Systematic Reviews online databases for studies published from 1996 to 2020 that included ≥10 PCD adult and/or paediatric patients.

RESULTS

We included 102 studies (7289 patients). 83 studies reported on spirometry, 11 on body plethysmography, 15 on multiple-breath washout, 36 on high-resolution computed tomography (HRCT), 57 on microbiology and 17 on health-related quality of life. Measurement and reporting of outcomes varied considerably between studies (e.g. different scoring systems for chest HRCT scans). Additionally, definitions of outcome measures varied (e.g. definition of chronic colonisation by respiratory pathogen), impeding direct comparisons of results.

CONCLUSIONS

This review highlights the need for standardisation of measurements and reporting of outcome measures to enable comparisons between studies. Defining a core set of clinical outcome measures is necessary to ensure reproducibility of results and for use in future trials and prospective cohorts.

An Animated Functional Data Analysis Interface to Cluster Rapid Lung Function Decline and Enhance Center-Level Care in Cystic Fibrosis

Identifying disease progression through enhanced decision support tools is key to chronic management in cystic fibrosis at both the patient and care center level. Rapid decline in lung function relative to patient level and center norms is an important predictor of outcomes. Our objectives were to construct and utilize center-level classification of rapid decliners to develop an animated dashboard for comparisons within patients over time, multiple patients within centers, or between centers. A functional data analysis technique known as functional principal components analysis was applied to lung function trajectories from 18,387 patients across 247 accredited centers followed through the United States Cystic Fibrosis Foundation Patient Registry, in order to cluster patients into rapid decline phenotypes. Smaller centers (<30 patients) had older patients with lower baseline lung function and less severe rates of decline and had maximal decline later, compared to medium (30-150 patients) or large (>150 patients) centers. Small centers also had the lowest prevalence of early rapid decliners (17.7%, versus 24% and 25.7% for medium and large centers, resp.). The animated functional data analysis dashboard illustrated clustering and center-specific summaries of the rapid decline phenotypes. Clinical scenarios and utility of the center-level functional principal components analysis (FPCA) approach are considered and discussed.

Official ERS technical standard: Global Lung Function Initiative reference values for static lung volumes in individuals of European ancestry

BACKGROUND

Measurement of lung volumes across the life course is critical to the diagnosis and management of lung disease. The aim of the study was to use the Global Lung Function Initiative methodology to develop all-age multi-ethnic reference equations for lung volume indices determined using body plethysmography and gas dilution techniques.

METHODS

Static lung volume data from body plethysmography and gas dilution techniques from individual, healthy participants were collated. Reference equations were derived using the LMS (lambda-mu-sigma) method and the generalised additive models of location shape and scale programme in R. The impact of measurement technique, equipment type and being overweight or obese on the derived lung volume reference ranges was assessed.

RESULTS

Data from 17 centres were submitted and reference equations were derived from 7190 observations from participants of European ancestry between the ages of 5 and 80 years. Data from non-European ancestry populations were insufficient to develop multi-ethnic equations. Measurements of functional residual capacity (FRC) collected using plethysmography and dilution techniques showed physiologically insignificant differences and were combined. Sex-specific reference equations including height and age were developed for total lung capacity (TLC), FRC, residual volume (RV), inspiratory capacity, vital capacity, expiratory reserve volume and RV/TLC. The derived equations were similar to previously published equations for FRC and TLC, with closer agreement during childhood and adolescence than in adulthood.

CONCLUSIONS

Global Lung Function Initiative reference equations for lung volumes provide a generalisable standard for reporting and interpretation of lung volumes measurements in individuals of European ancestry.

The impact of changing to the Global Lung Function Initiative reference equations for transfer factor in paediatrics

The Global Lung Function Initiative (GLI) all-age reference equations for carbon monoxide transfer factor were published in 2017 and endorsed by the European Respiratory Society and American Thoracic Society. In order to understand the impact of these new reference equations on the interpretation of results in children referred from haematology and oncology paediatric services, we retrospectively analysed transfer factor results from any paediatric patient referred from haematology/oncology in the period 2010–2018. We examined transfer factor of the lung for carbon monoxide (T_LCO), transfer coefficient of the lung for carbon monoxide (K_CO) and alveolar volume (V_A) from 241 children (age range 7–18 years, 130 male). The predicted values from Rosenthal and GLI were plotted against height. The difference in interpretation of results was analysed by looking at the percentage of patients below the lower limit of normal for each parameter. Overall, the Rosenthal predicted values for T_LCO were higher than those predicted by GLI. Predicted K_CO using Rosenthal was higher in all observations. In contrast, the Rosenthal predicted V_A was generally lower than the GLI value. The GLI predicted values for transfer factor show considerable differences compared with currently used paediatric UK reference values, differences that will have a significant impact on interpretation of results.

There will be significant clinical differences in the results of transfer factor when switching to the GLI-2017 from Rosenthal-1993 reference values, strongly recommending implementing the use of GLI-2017 reference equations for paediatricshttps://bit.ly/3o0zR4f

Comparing Spirometric Reference Values From Childhood to Old Age Estimated by LMS and Linear Regression Models

BACKGROUND

Proper reference values for lung function testing are essential for achieving adequate interpretations. The LMS procedure (lambda, mu, sigma) permits continuous analyses of entire populations avoiding gaps in the transition between childhood and adulthood. It also allows more precise calculations of average values, dispersion, and 5th percentiles, which are usually considered the lower limit of normality. The objective of this study was to compare our results fitted with the LMS method with standard multiple linear regression, and with those from international Global Lung Function Initiative (GLI) equations.

METHODS

Data from 9835 healthy residents of the metropolitan area of Mexico City aged 8-80 years were compiled from several studies: EMPECE, PLATINO, adult Mexican workers and two unpublished studies. The LMS procedure and multiple linear regression models were fit to obtain reference equations using R software.

RESULTS

Residuals from the LMS models had a median closer to zero, and smaller dispersion than those from the linear model, but differences although statistically significant were very small and of questionable practical relevance. For example, for females and ln(FEV₁), median residual was -0.001 with p25 of -0.08 and p75 of 0.08 for LMS, compared with 0.004 (-0.08, 0.09) [p<0.05] for the linear model. Average spirometric values for a given height for our population, were higher than those predicted by the GLI study.

CONCLUSION

Continuous reference equations for the Mexican population calculated using the LMS technique showed slightly better fit than linear regression models.

Clustered randomized controlled trial of a clinic-based problem-solving intervention to improve adherence in adolescents with cystic fibrosis

BACKGROUND

In Cystic Fibrosis (CF), adherence to pulmonary medications is about 50% and decreases during adolescence. Effective interventions have not been integrated into CF care. This effectiveness study tested a brief, clinic-based behavioral intervention to improve adherence.

METHODS

iCARE (I Change Adherence and Raise Expectations) was a pragmatic, clustered, 2-arm randomized controlled trial at 18 CF Centers. 607 adolescents with CF, ages 11-20 years, participated. Centers were randomized to IMPACT (n = 9; 300 adolescents), a brief problem-solving + education intervention, or standard care (SC; n = 9; 307 adolescents). IMPACT was delivered during a regularly scheduled clinic visit by a member of the clinical care team. The primary outcome was composite pulmonary medication possession ratio (cMPR); secondary endpoints were lung function, Body Mass Index percentile, courses of IV antibiotics, and health-related quality of life at 12 months.

RESULTS

Effectiveness of the intervention was tested using mixed models, generalized estimating equations comparing IMPACT to SC. Fifty-eight percent of problem-solving sessions targeted barriers to airway clearance, exercise or nutrition, while 18% addressed pulmonary medications. Average intervention fidelity score was 67% (SD = 14%; Range = 25-100%). No significant intervention effects were found for cMPR or any of the secondary outcomes compared to SC.

CONCLUSIONS

The IMPACT intervention did not improve medication adherence or health outcomes over 12 months. Challenges to implementing the intervention as intended during busy clinic visits were identified.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01232478; URL: www.clinicaltrials.gov.

Identifying exceptional cystic fibrosis care services: combining statistical process control with focus groups

Background

The Cystic Fibrosis (CF) Registry collects clinical data on all patients attending specialist CF centres in the UK. These data have been used to make comparisons between centres on key outcomes such as forced expiratory volume in 1 second (FEV1) using simple rankings, which promote the assumption that those with the highest measures provide ‘better’ care.

Objectives

To explore whether or not using statistical ‘process control’ charts that move away from league tables and adjusting for case mix (age, where appropriate; sex; CF genotype; pancreatic sufficiency; and socioeconomic status) could identify exceptional CF care services in terms of clinically meaningful outcomes. Then, using insight from patients and clinicians on what structures, processes and policies are necessary for delivering good CF care, to explore whether or not care is associated with observed differences in outcomes.

Design

Cross-sectional analyses.

Setting

Specialist CF centres in the UK.

Participants

Patients aged ≥ 6 years attending specialist CF centres and clinicians at these centres.

Main outcome measures

FEV1% predicted.

Data sources

Annual reviews taken from the UK CF Registry (2007–15).

Results

We studied FEV1 in many different ways and in different periods. In our analyses of both adult and paediatric centres, we observed that some centres showed repeated evidence of ‘special-cause variation’, with mean FEV1 being greater than the mean in some cases and lower than the mean in others. Some of these differences were explained by statistical adjustment for different measures of case mix, such as age, socioeconomic status, genotype and pancreatic sufficiency. After adjustment, there was some remaining evidence of special-cause variation for some centres. Our data at these centres suggest that there may be an association with the use of intravenous antibiotics. Workshops and focus groups with clinicians at paediatric and adult centres identified a number of structures, processes and policies that were felt to be associated with good care. From these, questionnaires for CF centre directors were developed and disseminated. However, the response rate was low, limiting the questionnaires’ use. Focus groups with patients to gain their insights into what is necessary for the delivery of good care identified themes similar to those identified by clinicians, and a patient questionnaire was developed based on these insights.

Limitations

Our data analyses suggest that differences in intravenous antibiotic usage may be associated with centre-level outcomes; this needs to be explored further in partnership with the centres. Our survey of centre directors yielded a low response, making it difficult to gain useful knowledge to inform further discussions with sites.

Conclusions

Our findings confirm that the CF Registry can be used to identify differences in clinical outcomes between centres and that case mix might explain some of these differences. As such, adjustment for case mix is essential when trying to understand how and why centres differ from the mean.

Future work

Future work will involve exploring with clinicians how care is delivered so that we can understand associations between care and outcomes. Patients will also be asked for their perspectives on the care they receive.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.

Improving Detection of Rapid Cystic Fibrosis Disease Progression-Early Translation of a Predictive Algorithm Into a Point-of-Care Tool

The clinical course of cystic fibrosis (CF) lung disease is marked by acute drops of lung function, defined clinically as rapid decline. As such, lung function is monitored routinely through pulmonary function testing, producing hundreds of measurements over the lifespan of an individual patient. Point-of-care technologies aimed at improving detection of rapid decline have been limited. Our aim in this early translational study is to develop and translate a predictive algorithm into a prototype prognostic tool for improved detection of rapid decline. The predictive algorithm was developed, validated and checked for 6-month, 1-year, and 2-year forecast accuracies using data on demographic and clinical characteristics from 30 879 patients aged 6 years and older who were followed in the U.S. Cystic Fibrosis Foundation Patient Registry from 2003 to 2015. Predictions of rapid decline based on the algorithm were compared to a detection algorithm currently being used at a CF center with 212 patients who received care between 2012-2017. The algorithm was translated into a prototype web application using RShiny, which resulted from an iterative development and refinement based on clinician feedback. The study showed that the algorithm had excellent predictive accuracy and earlier detection of rapid decline, compared to the current approach, and yielded a prototype platform with the potential to serve as a viable point-of-care tool. Future work includes implementation of this clinical prototype, which will be evaluated prospectively under real-world settings, with the aim of improving the pre-visit planning process for CF point of care. Likely extensions to other point-of-care settings are discussed.

Lung function in patients with primary ciliary dyskinesia: an iPCD Cohort study

Primary ciliary dyskinesia (PCD) has been considered a relatively mild disease, especially compared to cystic fibrosis (CF), but studies on lung function in PCD patients have been few and small.This study compared lung function from spirometry of PCD patients to normal reference values and to published data from CF patients. We calculated z-scores and % predicted values for forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) using the Global Lung Function Initiative 2012 values for 991 patients from the international PCD Cohort. We then assessed associations with age, sex, country, diagnostic certainty, organ laterality, body mass index and age at diagnosis in linear regression models. Lung function in PCD patients was reduced compared to reference values in both sexes and all age groups. Children aged 6-9 years had the smallest impairment (FEV₁ z-score -0.84 (-1.03 to -0.65), FVC z-score -0.31 (-0.51 to -0.11)). Compared to CF patients, FEV₁ was similarly reduced in children (age 6-9 years PCD 91% (88-93%); CF 90% (88-91%)), but less impaired in young adults (age 18-21 years PCD 79% (76-82%); CF 66% (65-68%)). The results suggest that PCD affects lung function from early in life, which emphasises the importance of early standardised care for all patients.

Using different methods to process forced expiratory volume in one second (FEV 1) data can impact on the interpretation of FEV 1 as an outcome measure to understand the performance of an adult cystic fibrosis centre: A retrospective chart review

Background: Forced expiratory volume in one second (FEV 1) is an important cystic fibrosis (CF) prognostic marker and an established endpoint for CF clinical trials. FEV 1 is also used in observation studies, e.g. to compare different centre's outcomes. We wished to evaluate whether different methods of processing FEV 1 data can impact on a centre's outcome. Methods: This is a single-centre retrospective analysis of routinely collected data from 2013-2016 which included 208 adults with CF. Year-to-year %FEV 1 change was calculated by subtracting best %FEV 1 at Year 1 from Year 2 (i.e. negative values indicate %FEV 1 decline), and compared using Friedman test. Three methods were used to process %FEV 1 data. First, %FEV 1 calculated with Knudson equation was extracted directly from spirometer machines. Second, FEV 1 volume were extracted then converted to %FEV 1 using clean height data and Knudson equation. Third, FEV 1 volume were extracted then converted to %FEV 1 using clean height data and GLI equation. In addition, %FEV 1 decline calculated using GLI equation was adjusted for baseline %FEV 1 to understand the impact of case-mix adjustment. Results: There was a trend of reduction in %FEV 1 decline with all three data processing methods but the magnitude of %FEV 1 decline differed. Median change in %FEV 1 for 2013-2014, 2014-2015 and 2015-2016 was -2.0, -1.0 and 0.0 respectively using %FEV 1 in Knudson equation whereas the median change was -1.1, -0.9 and -0.3 respectively using %FEV 1 in the GLI equation. A statistically significant p-value (0.016) was only obtained when using %FEV 1 in Knudson equation extracted directly from spirometer machines. Conclusions: Although the trend of reduction in %FEV 1 decline was robust, different data processing methods yielded varying results when %FEV 1 decline was compared using a standard related group non-parametric statistical test. Observational studies with %FEV 1 decline as an outcome measure should carefully consider and clearly specify the data processing methods used.

Using different methods to process forced expiratory volume in one second (FEV 1) data can impact on the interpretation of FEV 1 as an outcome measure to understand the performance of an adult cystic fibrosis centre: A retrospective chart review

Background: Forced expiratory volume in one second (FEV 1) is an important cystic fibrosis (CF) prognostic marker and an established endpoint for CF clinical trials. FEV 1 is also used in observation studies, e.g. to compare different centre's outcomes. We wished to evaluate whether different methods of processing FEV 1 data can impact on centre outcome. Methods: This is a single-centre retrospective analysis of routinely collected data from 2013-2016 among 208 adults. Year-to-year %FEV 1 change was calculated by subtracting best %FEV 1 at Year 1 from Year 2 (i.e. negative values indicate fall in %FEV 1), and compared using Friedman test. Three methods were used to process %FEV 1 data. First, %FEV 1 calculated with Knudson equation was extracted directly from spirometer machines. Second, FEV 1 volume were extracted then converted to %FEV 1 using clean height data and Knudson equation. Third, FEV 1 volume were extracted then converted to %FEV 1 using clean height data and GLI equation. In addition, year-to-year variation in %FEV 1 calculated using GLI equation was adjusted for baseline %FEV 1 to understand the impact of case-mix adjustment. Results: Year-to-year fall in %FEV 1 reduced with all three data processing methods but the magnitude of this change differed. Median change in %FEV 1 for 2013-2014, 2014-2015 and 2015-2016 was -2.0, -1.0 and 0.0 respectively using %FEV 1 in Knudson equation whereas the median change was -1.1, -0.9 and -0.3 respectively using %FEV 1 in the GLI equation. A statistically significant p-value (0.016) was only obtained when using %FEV 1 in Knudson equation extracted directly from spirometer machines. Conclusions: Although the trend of reduced year-to-year fall in %FEV 1 was robust, different data processing methods yielded varying results when year-to-year variation in %FEV 1 was compared using a standard related group non-parametric statistical test. Observational studies with year-to-year variation in %FEV 1 as an outcome measure should carefully consider and clearly specify the data processing methods used.

Modern assessment of pulmonary function in divers cannot rely on old reference values

INTRODUCTION

Pulmonary function testing (PFT) is an important part of dive medical examinations. Depending on the standard used to assess fitness to dive, different reference sets and fixed cut-off points are used. Reference values are part of an ongoing debate regarding the validity and accuracy related to different age groups, sex and ethnic backgrounds. The Global Lung Initiative (GLI) has provided an all-age reference set which corrects for sex and ethnicity (GLI-2012); this has had substantial impact on pulmonary medicine.

METHOD

We present an algorithm that can be used to standardise analysis of PFT in divers using the GLI-2012 reference set. Differences in the analysis of PFT between the ECSC/ERS-1993 and the GLI-2012 reference values are illustrated by means of three case reports.

CONCLUSION

Using a valid database of reference values increases accuracy and might prevent additional medical investigations and/or incorrect assessment of fitness to dive. Although our algorithm needs further evaluation to ensure its validity, the preliminary results are promising. Whatever algorithm is used, we urge dive medical physicians to consider using valid reference sets when analysing PFT for assessment of fitness to dive.

The multi-ethnic global lung initiative 2012 and Third National Health and Nutrition Examination Survey reference values do not reflect spirometric measurements in Black boys and men from Tanzania

The interpretation of spirometric results of Black Africans according to reference standards based on data from outside their native environment may lead to the wrong conclusions. This article aims to characterize the ventilatory capacity of boys and men from Tanzania according to forced expiratory volume in one second (FEV1 ), forced vital capacity (FVC), peak expiratory flow (PEF) and FEV1 /FVC based on the collected anthropological material and to compare them to NHANES III, Third National Health and Nutrition Examination Survey (NHANES III) African American predicted values and GLI2012 equations. The analysis included spirometric measurements of n = 295 participants from Tanzania. Pearson's correlation analysis and the backward stepwise multiple regression analysis were performed. FEV1 , FVC, PEF and FEV1 /FVC results were compared to the NHANES III African American predicted values as well as to the GLI2012 equations. FEV1 measurements are lower than the reference values according to NHANES III and GLI2012 equations by 22·1% and 25·8%. FVC results fell short of the NHANES III predicted by 29·5% and of GLI2012 by 32·5%. The average %FEV1 /FVC scores for the boys and men exceeded the recommended GLI2012 predicted by 10·5-15·2%. All the spirometric measurements included in the analysis were statistically significantly correlated with age, body height, sitting height, trunk length and body weight. The application of prediction formulae developed for non-African populations overestimates the values for Black Africans. The results of spirometric measurements are ecosensitive and dependent on various external (environmental) factors.

Early Detection of Rapid Cystic Fibrosis Disease Progression Tailored to Point of Care: A Proof-of-Principle Study

Slowing cystic fibrosis (CF) lung disease progression is crucial to survival, but point-of-care technologies aimed at early detection-and possibly prevention-of rapid lung function decline are limited. This proof-of-principle study leverages a rich national patient registry and follow-up data on a local CF cohort to build an algorithm and prototype prognostic tool aimed at early detection of rapid lung function decline. The algorithm was developed using a novel longitudinal analysis of lung function (measured as forced expiratory volume in 1 s of % predicted, FEV1). Covariates included clinical and demographic characteristics selected from the registry based on information criterion. Preliminary assessment of algorithm performance suggested excellent predictive accuracy and earlier detection of rapid decline than standard of care being applied at a local center. Graphical displays were presented and evaluated for clinical utility. Predictions from the algorithms and chosen graphical displays were translated into a prototype web application using RShiny and underwent iterative development based on clinician feedback. This paper suggests that the algorithm and its translation could offer a means for earlier detection and treatment of rapid decline, providing clinicians with a viable point-of-care technology to intervene prior to irreversible lung damage.

Phenotypes of Rapid Cystic Fibrosis Lung Disease Progression during Adolescence and Young Adulthood

RATIONALE

Individuals with cystic fibrosis are at risk for prolonged drops in lung function, clinically termed rapid decline, during discreet periods of the disease.

OBJECTIVES

To identify phenotypes of rapid pulmonary decline and determine how these phenotypes are related to patient characteristics.

METHODS

A longitudinal cohort study of patients with cystic fibrosis aged 6-21 years was conducted using the Cystic Fibrosis Foundation Patient Registry. A statistical approach for clustering longitudinal profiles, sparse functional principal components analysis, was used to classify patients into distinct phenotypes by evaluating trajectories of FEV1 decline. Phenotypes were compared with respect to baseline and mortality characteristics.

MEASUREMENTS AND MAIN RESULTS

Three distinct phenotypes of rapid decline were identified, corresponding to early, middle, and late timing of maximal FEV1 loss, in the overall cohort (n = 18,387). The majority of variation (first functional principal component, 94%) among patient profiles was characterized by differences in mean longitudinal FEV1 trajectories. Average degree of rapid decline was similar among phenotypes (roughly -3% predicted/yr); however, average timing differed, with early, middle, and late phenotypes experiencing rapid decline at 12.9, 16.3, and 18.5 years of age, respectively. Individuals with the late phenotype had the highest initial FEV1 but experienced the greatest loss of lung function. The early phenotype was more likely to have respiratory infections and acute exacerbations at baseline or to develop them subsequently, compared with other phenotypes.

CONCLUSIONS

By identifying phenotypes and associated risk factors, timing of interventions may be more precisely targeted for subgroups at highest risk of lung function loss.

Global Lung Function Initiative 2012 reference values for spirometry in South Italian children

RATIONALE

Despite the widespread use of the Global Lung Function Initiative (GLI) 2012 reference values, there is still the need of testing their applicability in local areas.

OBJECTIVES

The aims of this study are to evaluate applicability of GLI reference equations in a large population-based sample of normal schoolchildren from Sicily, and to compare GLI and previous prediction equations in terms of spirometry test interpretation.

METHODS

GLI equations were evaluated in 1243 normal schoolchildren, 49% males, aged 7-16 years, height 116-187 cm. Normality assumptions for the GLI z-scores (FEV₁, FVC, FEV₁/FVC) were tested, and bootstrap confidence intervals for the mean (0 expected) and the variance (1 expected) were derived. GLI and other reference equations were compared in terms of probabilities to fall below the lower limit of normal (LLN).

RESULTS

The GLI z-score normality assumption held for males but not for females (p < 0.001). According to the mean z-score, predicted values were: slightly underestimated for FEV₁ (0.15 in males, 0.07 in females); overestimated for FVC (-0.27 in males, -0.32 in females); highly underestimated for FEV₁/FVC (0.75 in males, 0.81 in females). Variability was correctly estimated. The probability of FEV₁<LLN correctly approached 0.05 when using GLI, Hankinson and Quanjer equations. Wang equations yielded correct probabilities of abnormal FVC; Pistelli equations yielded correct probabilities of abnormal FEV₁/FVC for females.

CONCLUSIONS

GLI 2012 references underestimate FEV₁/FVC predicted values in a sample of normal South Italian children. Physicians interpreting spirometry should be aware to test reference values prior to their use in a local area.

Comparison of FEV1 reference equations for evaluating a cystic fibrosis therapeutic intervention

OBJECTIVES

The Global Lung Function Initiative (GLI, 2012) developed reference equations for forced expiratory volume in 1 s (FEV₁ ). Previous equations were developed by groups led by Knudson (1983), Wang (1993), Hankinson (1999), and Stanojevic (2008).^1,2,4,6 We assessed how different prediction equations affect the conclusions from a therapeutic intervention study that evaluated the rate of percent predicted FEV₁ (ppFEV₁ ) decline.

METHODOLOGY

Using data from the Epidemiologic Study of cystic fibrosis (CF), we re-analyzed our previous study evaluating the relationship of dornase alfa (DA) use with ppFEV₁ using the Knudson, Wang & Hankinson, Stanojevic, and GLI equations. The change in intercept and change in slope of ppFEV₁ from a 2-year pre-index period and 2-year post-index period were compared between the treated (N = 2483) and comparator groups (N = 6992, from 4110 unique patients).

RESULTS

Change in intercept for the comparator group was similar across equations except that Wang & Hankinson values were more negative. The difference in change in intercept between the DA and comparator groups ranged from 3.38 to 4.02% predicted. The change in slope for the comparator group ranged from -0.58 to +0.30 ppFEV₁ /year, but the difference in change in slope between the DA and comparator groups was in a narrower range from +0.53 to +0.89 ppFEV₁ /year.

CONCLUSIONS

Although individual patient results are impacted by the choice of reference equations, the study conclusions from this evaluation of a therapeutic intervention were minimally affected. GLI equations are recommended for future studies, but prior results based on other equations should be accepted as reliable.

Early detection of lung function decrements in children and adolescents with cystic fibrosis using new reference values

Interpretation of lung function values in children with cystic fibrosis (CF) depends on the applied reference values. We hypothesize that differences between the new global lung function initiative (GLI) values and the formerly used Zapletal et al. values produce significantly different clinical results. We analyzed 3719 lung function measurements of 108 children and adolescents (n = 54 male; aged 6-18 years) with CF treated between September 1991 and July 2009. Data were analyzed in milliliters (ml) and % predicted (pred.) and interpreted using Zapletal and GLI reference values. Applying GLI compared to Zapletal resulted in significantly lower mean forced expiratory volume in 1s (FEV1)% pred.

VALUES

Zapletal 86.6% (SD 20.6), GLI 79.9% (SD 20.3) and 32% (n = 497/1543) were misclassified as normal when using Zapletal. Despite showing no overall differences in FEV1 and forced vital capacity (FVC) between concomitant Pseudomonas detection (PA+) in n = 938 and Pseudomonas negative (PA-) (n = 2781) using either reference PA+ resulted in lower FEV1 and FVC values with increasing age; however, measurement of small airway obstruction with forced expiratory flow at 75% of FVC (FEF75) values - available for Zapletal -showed significant differences. Reassurance regarding lung function when using old reference values may occur with potential clinical significance. Discrepancies in lung function interpretation underline the importance of using uniform and best available reference values.

Ethnicity impacts the cystic fibrosis diagnosis: A note of caution

BACKGROUND

The diagnosis of Cystic Fibrosis (CF) is by consensus based on the same parameters in all patients, yet the influence of ethnicity has only scarcely been studied. We aimed at elucidating the impact of Asian descent on the diagnosis of CF.

METHODS

We performed a retrospective analysis of the CFTR2 and UK CF databases for clinical phenotype, sweat chloride values and CFTR mutations and compared the diagnostic characteristics of Asian to non-Asian patients with CF.

RESULTS

Asian patients with CF do not have a worse clinical phenotype. The repeatedly reported lower FEV₁ of Asian patients with CF is attributable to the influence of ethnicity on lung function in general. However, pancreatic sufficiency is more common in Asian patients with CF. The diagnosis of CF in people with Asian ancestry is heterogeneous as mean sweat chloride values are lower (92±26 versus 99±22mmol/L in controls) and 14% have sweat chloride values below 60mmol/L (versus 6% in non-Asians). Also, CFTR mutations differ from those in Caucasians: 55% of British Asian patients with CF do not have one mutation included in the routine newborn screening panel.

CONCLUSIONS

Bringing together the largest cohort of patients with CF and Asian ethnicity, we demonstrate that Asian roots impact on all three CF diagnostic pillars. These findings have implications for clinical practice in the increasingly ethnically diverse Western population.

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

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

Respiratory sleep disturbance in children and adolescents with cystic fibrosis

Sleep disturbance has been described in cystic fibrosis (CF) patients as relevant to clinical and lung function predictive factors helping to improve the diagnosis and early intervention. Related paediatric studies are scarce.

OBJECTIVE

To describe respiratory sleep disturbance (RSD) and its association with spirometric indices in a population of CF children. A second aim was to determine if spirometric indices and wake-time SpO2 are predictors of sleep disturbance.

METHODS

A cross-sectional study involving 33CF paediatric patients. All participants underwent in-lab polysomnography (PSG), pulse oximetry and spirometry. A standardized sleep questionnaire was completed for each patient. Two subgroups were considered: I - Normal (FEV1>-1.64 z-score); II - Obstructed (FEV1≤-1.64 z-score).

RESULTS

Participant's median age was 12 (6-18) years, 16 (48.5%) were male. Twenty-nine patients (87.9%) presented sleep complaints. Sleep efficiency was reduced; sleep latency and waking after sleep onset (WASO) increased. N1 increased, N2, N3, REM and awakenings were normal. The apnoea-hypopnoea index was 0.6/h (sd 0.9); respiratory disturbance index (RDI) was 6.6/h (sd 5.2). Mean awaking (97% (sd 1.1)) and sleep SpO2 (95% (sd 2.7)) were normal; mean nocturnal oximetry desaturation index was 2.36/h; minimal nocturnal SpO2 was 89% (sd 4.1). We found associations between mean nocturnal SPO2 and mean values of FEV1 (r=0.528; p=0.002) and FEF25-75 (r=0.426; p=0.013). There were significant differences in nocturnal SpO2 between normal and obstructed patients (p<0.000). PSG data correlated with the questionnaire answers for night awakenings and WASO (p=0.985) and difficult breathing during sleep and RDI (p=0.722). This study points to most CF children having sleep complaints, and highlights the correlation between subjective assessment of sleep and PSG and spirometric results. Awake-time SpO2 and spirometric values are possible risk predictors for nocturnal desaturation.

The Influence of the Reference Values on the Interpretation of Lung Function in Children: Comparison of Global Lung Initiative 2012 and Polish 1998 Reference Values

Interpretation of spirometry strongly depends on the applied predicted values. New Global Lung Initiative (GLI) reference values have recently been published but their influence on spirometry interpretation in children has not been widely evaluated. The aim of the study was to compare the interpretation of spirometry using GLI-2012 vs. Polish-1998 reference values. Spirometry results of 315 Caucasian children aged 4-18 were analyzed. Airway obstruction was defined as FEV1/FVC<LLN (lower limit of normal: 5th percentile, -1,64 standard deviation), while restrictive ventilatory pattern as FVC<LLN and FEV1/FVC>LLN. The findings were that FEV1 and FVC expressed as GLI-2012 or Polish-1998 z-scores differed significantly (p<0.05). The mean FEV1 z-score was -0.68±1.25 vs. -0.13±1.70 and the mean FVC was -0.34±1.08 vs. 0.30±1.15 for GLI-2012 and Polish-1998, respectively. There was no difference for FEV1/FVC z-scores. Obstructive and restrictive ventilatory patterns were diagnosed in 20.3% and 7.6% children using GLI-2012 values compared with 17.5% and 3.8% when using Polish-1998 reference values, respectively. In conclusion, the use of GLI-2012 reference values in the population of Polish children increases the number of detected lung function abnormalities compared with Polish-1998 reference values.

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.

[New international reference values for spirometry: implications for clinical issues using a comparative analysis of a paediatric population]

BACKGROUND

The new lung function reference values of the global lung initiative (GLI) are recommended by most health societies. The aim of this study was to analyze FEV1- and FEV1/FVC-values from a German and Austrian patient group applying old and new reference values.

RESULTS

A total of 215 Caucasian children (aged 5-17 years) were included. FEV1-values were significantly lower applying GLI reference values compared to Zapletal values (median 96.9 % pred. (87.3-105.2) versus 100.6 % pred. (quartile 91.5-111.4), p = 0.000), the median difference was 4.9 % (range -12.9 to 27.5) % pred. Differences correlated significantly with age and FEV1 in % predicted (Zapletal), p = 0.000 17/70 (24 %) patients with cystic fibrosis had FEV1-values <80% pred. applying Zapletal, in 25 (36 %) patients FEV1 was abnormal (z-score <1645) using GLI values; 3/145 asthmatics (2 %) had FEV1-Werte <80 % d.S. (Zapletal), 7/145 (5 %) z-scores <1645 (GLI).

CONCLUSION

Differences between GLI-and Zapletal-reference values were considerable in pediatric asthma and CF-patients.

Antibiotic treatment of signs and symptoms of pulmonary exacerbations: a comparison by care site

BACKGROUND

Antibiotic treatment of cystic fibrosis pulmonary exacerbations is inconsistent. Previous research has indicated that intravenous antibiotics are used more frequently at sites with better pulmonary function but it is not clear under what circumstances they are prescribed.

METHOD

Pediatric care sites enrolled in the Epidemiologic Study of Cystic Fibrosis were ranked by median FEV1 % predicted of children they followed. Reported presence of new signs and symptoms of a pulmonary exacerbation (PEx) and antibiotic treatment within 21 days were compared between those in the highest vs. those in the other quartiles, and adjusted for sociodemographic and clinical characteristics of patients.

RESULT

Highest quartile sites had a total of 2,454 children eligible for this analysis; lower quartile sites had a total of 5,487. The odds of having a PEx at highest vs. lower sites varied with how the PEx was defined, but high quartile sites were uniformly more likely to treat PEx with antibiotics. The adjusted odds ratio for treatment with any antibiotics of a PEx defined by the occurrence of one or two new signs and symptoms was 1.24 (95% CI 1.10, 1.40); for treatment of a PEx defined by the occurrence of three or four new signs and symptoms was 1.50 (95% CI 1.06, 2.11); and for treatment of a PEx defined by a drop of FEV(1) by ≥-15% was 1.33 (1.10, 1.60). The adjusted OR for treatment of these PEx with IV antibiotics was 1.11 (0.94, 1.32), 1.90 (1.32, 2.72), and 1.33 (1.10, 1.60), respectively.

CONCLUSION

ESCF care sites in the highest quartile for FEV(1) were more likely to prescribe antibiotics when patients present with either mild or overt evidence of PEx. While this may not be the only reason that their patients have superior median FEV(1), it is likely an important contributor.

Improvements in lung function and height among cohorts of 6-year-olds with cystic fibrosis from 1994 to 2012

OBJECTIVE

To characterize spirometry and height changes in cohorts of 6-year-old children with cystic fibrosis (CF).

STUDY DESIGN

Global Lung Initiative forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC, and the Centers for Disease Control and Prevention height-for-age (HFA) z-scores were generated for 6-year-old children from the Cystic Fibrosis Foundation Patient Registry each year between 1994 and 2012. Z-score mean differences were analyzed by the t test, and time trends of means were analyzed by least squares regression for all children and for subgroups of sex, F508del mutation genotype, Medicaid insurance, and prenatal/newborn screening identification. Z-score distributions were compared using the 2-sample Kolmogorov-Smirnov test.

RESULTS

A total of 11 670 children with CF were studied, of whom 50.5% were males, 50.2% had the F508del/F508del genotype, and 46.6% were insured by Medicaid. Mean HFA, FEV1, and FVC z-scores increased significantly over the period in the entire cohort and in all subgroups (P < .001), but FEV1/FVC z-scores were below normal and did not change significantly. In 2012, children identified by screening had significantly higher mean HFA (P = .002), FEV1 (P < .001), and FVC (P < .001) z-scores compared with children not screened, with 90% of FVC and 71.4% of FEV1z-scores greater than predicted by the normal distribution. FEV1/FVC z-scores were not different between the children who were and were not screened.

CONCLUSION

Consistent, significant increases in HFA, FEV1, and FVC occurred between 1994 and 2012, but FEV1/FVC, a measure of airway obstruction, did not change appreciably during this period. FVC and FEV1z-score distributions suggest that normative equation reference populations underpredict lung volumes of children with CF, but the reasons for this remain unclear.

Putting lung function and physiology into perspective: cystic fibrosis in adults

Adult cystic fibrosis (CF) is notable for the wide heterogeneity in severity of disease expression, both between patients and within the lungs of individuals. Although CF airways disease appears to start in the small airways, in adults there is typically widespread bronchiectasis, increased airway secretions, and extensive obstruction and inflammation of the small airways. The complexity and heterogeneity of airways disease in CF means that although there are many different methods of assessing and describing lung 'function', none of these single-dimensional tests is able to provide a comprehensive assessment of lung physiology across the spectrum seen in adult CF. The most widely described measure, the forced expiratory volume in 1 s, remains a useful and simple clinical tool, but is insensitive to early changes and may be dissociated from other more detailed assessments of disease severity such as computed tomography. In this review, we also discuss the use of more sensitive novel assessments such as multiple breath washout tests and impulse oscillometry, as well as the role of cardiopulmonary exercise testing. In the future, hyperpolarized gas magnetic resonance imaging techniques that combine regional structural and functional information may help us to better understand these measures, their applications and limitations.

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.