Etiology of ethnic differences in childhood spirometry

Machine learning-based spirometry reference values for the Iranian population: a cross-sectional study from the Shahedieh PERSIAN cohort

Objective

This study aimed to determine spirometric norm values for the healthy Iranian adult population and compare them with established norm equations, specifically the GLI-Caucasian and Iranian equations.

Methods

During the recruitment phase of the Shahedieh Prospective Epidemiological Research Studies in Iran (PERSIAN) in 2016, spirometric parameters of 998 participants were obtained. KNN regression was used to extract reference values for spirometric parameters FEV1, FVC, FEV1/FVC, and FEF25-75%, considering height and age as features. The performance of KNN regression was compared with conventional models used in previous studies, such as the multiple linear regression (MLR) model and the Lambda-Mu-Sigma (LMS) model. The predicted values were compared with those obtained from the GLI-Caucasian and Iranian equations. The validation criterion was the mean squared error (MSE) based on 5-fold cross-validation.

Results

This study included 473 female participants and 525 male participants. KNN regression provided more accurate predictions for four spirometric parameters than MLR and LMS. The MSE for predicting FVC in female participants was 0.159, 0.169, and 0.165 in KNN regression, MLR, and LMS, respectively. The predictions of the present study were closer to the actual values of the reference population for four indicators compared to the prediction values using two sets of reference equations. The MSE of predicted FVC for female participants was 0.159 in the present study, which was less than the Iranian (MSE = 0.344) and GLI-Caucasian (MSE = 0.397) equations.

Conclusion

Using a flexible machine learning approach, this study established spirometry reference values specifically for the Iranian population. Recognizing that spirometry reference values vary among different populations, the Excel calculator developed in this research can be a valuable tool in healthcare centers for assessing lung function in Iranian adults.

Compatibility of the global lung function 2012 spirometry reference values in children, adolescents and young adults: a systematic review

INTRODUCTION

The Global Lung Function Initiative (GLI 2012) has published multiethnic spirometry reference values. To identify studies that evaluated the compatibility (applicability, validity, representativeness, agreement and/or adequacy) of the reference equations proposed by the GLI 2012 for spirometry tests in different populations.

METHODS

Systematic searches were carried out on the PubMed, LILACS (Latin American and Caribbean Health Sciences Literature), Scopus, Web of Science and Google Scholar databases. Cross-sectional observational studies published between 2012 and 2013 onwards that evaluated the compatibility of the GLI 2012 in children, adolescents and young adults (3-20 years old) were included. The references were manually searched and the Joanna Briggs Institute Critical Appraisal Checklist for Cross-Sectional Analytical Studies was applied to assess the methodological quality of the studies included.

RESULTS

All of the 5632 studies identified were classified as low risk of bias, but only 21 were deemed eligible for inclusion. Of these, 8 reported satisfactory GLI 2012 compatibility for their populations (Argentina, Spain, Columbia, Djibouti, Norway, Poland, Jordan and Zimbabwe), 5 cautious applicability, and the remaining 8 considered the equation unsatisfactory, since it over or underestimated spirometric parameters.

CONCLUSION

The GLI 2012 equations are not applicable to all populations and must be tested before being adopted.

Applicability of the Global Lung Function Initiative prediction equations in Hong Kong Chinese children

BACKGROUND AND OBJECTIVE

This study aimed to assess the applicability of the Global Lung Function Initiative (GLI) prediction equations for spirometry in Hong Kong children and to develop prediction equations based on the Generalized Additive Models for Location, Scale, and Shape (GAMLSS) modeling.

METHODS

Healthy Chinese children and adolescents aged 6-17 years old were recruited from randomly selected schools to undergo spirometry. The measurements were transformed to z-score according to the GLI-2012 equations for South East (SE) Asians and the GLI-2022 global race-neutral equations. Prediction equations for spirometric indices were developed with GAMLSS modeling to identify predictors.

RESULTS

A total of 886 children (477 boys) with a mean age of 12.5 years (standard deviation [SD] 3.3 years) were included. By the GLI-2012 SE Asian equations, positive mean z-scores were observed in forced expiratory volume in 1 s (FEV1 ) (boys: 0.138 ± SD 0.828; girls: 0.206 ± 0.823) and forced vital capacity (FVC) (boys: 0.160 ± 0.930; girls: 0.310 ± 0.895) in both sexes. Negative mean z-scores were observed in FEV1 /FVC ratio (boys: -0.018 ± 0.998; girls: -0.223 ± 0.897). In contrast, negative mean z-scores in FEV1 and FVC, and positive mean z-scores in FEV1 /FVC were observed when adopting the GLI-2022 race-neutral equations. The mean z-scores were all within the range of ±0.5. By GAMLSS models, age and height were significant predictors for all four spirometric indices, while weight was an additional predictor for FVC and FEV1 .

CONCLUSION

Our study provided data supporting the applicability of the GLI prediction equations in Hong Kong Chinese children. The GLI-2012 equations may underestimate FEV1 and FVC, while the GLI-2022 equations may overestimate the parameters, but the differences lie within the physiological limits. By GAMLSS modeling, weight was an additional predictor for FVC and FEV1 .

Normal spirometry prediction equations for the Iranian population

BACKGROUND

This study aimed to establish normative spirometric equations in a healthy population of Iranian children and adults, and compare these equations with those developed by the Caucasian Global Lung Initiative (GLI) for the first time.

METHODS

Spirometric data from healthy Iranian aged 4-82 years sampled in 2019 were used to derive reference equations using the generalized additive model for location (mu), shape (lambda), and scale (sigma).

RESULTS

A total of 418 females and 204 males were included in the study. Applying the GLI standards for the Iranian population resulted from the Z scores of FEV₁, FVC, FEV₁/FVC, and FEF_25-75% was not different from zero. Based on the newly calculated LLN, eleven individuals showed significant values below the LLN for FEV₁/FVC. In all age groups, this frequency was less than 5%, except for men over 70 years of age, which was 12.5%. There are significant differences between new data and GLI for Caucasian data.

CONCLUSION

It is recommended that the values and equations generated from this study should be used by physicians and technicians in their routine practice for the diagnosis and assessment of pulmonary disorders.

Isolated night cough in children: how does it differ from wheeze?

It has been postulated that some children with recurrent cough but no wheeze have a mild form of asthma (cough variant asthma), with similar risk factors and an increased risk of future wheeze.

This longitudinal study compared risk factors for isolated night cough and for wheeze in the Leicester Respiratory Cohort in children aged 1, 4, 6 and 9 years and compared prognosis of children with isolated night cough, children with wheeze and asymptomatic children.

We included 4101 children aged 1 year, 2854 aged 4 years, 2369 aged 6 years and 1688 aged 9 years. The prevalence of isolated night cough was 10% at age 1 year and 18% in older children. Prevalence of wheeze decreased from 35% at 1 year to 13% at 9 years. Although several risk factors were similar for cough and wheeze, day care, reflux and family history of bronchitis were more strongly associated with cough, and male sex and family history of asthma with wheeze. Over one-third of preschool children with cough continued to cough at school age, but their risk of developing wheeze was similar to that of children who were asymptomatic at earlier surveys. Wheeze tracked more strongly throughout childhood than cough.

In conclusion, our study showed that only some risk factors for cough and wheeze were shared but many were not, and there was little evidence for an increased risk of future wheeze in children with isolated night cough. This provides little support for the hypothesis that recurrent cough without wheeze may indicate a variant form of asthma.

Children with isolated night cough do not have an increased risk of future wheeze, and risk factors for cough and wheeze only partially overlap.https://bit.ly/31IbXSC

Predictors of obesity hypoventilation syndrome among patients with sleep-disordered breathing in India

Introduction

No study has been done in India to evaluate obesity hypoventilation syndrome (OHS) among patients with sleep-disordered breathing (SDB). The known predictors of OHS, i.e., body mass index (BMI) >35 kg/m² and forced vital capacity (FVC) <3.5 L for men and <2.3 L for women from western countries, cannot be applied to Indian patients.

Objectives

To find out the prevalence of OHS and to determine the predictors of OHS among Indian SDB patients.

Materials and Methods

It was a retrospective observational study conducted in a tertiary care institute from September 1, 2017, to August 31, 2018. All the patients who underwent polysomnography were analyzed for the presence of OHS. Of 85 patients referred for polysomnography, 76 had SDB. Thirteen patients were excluded because of hypoventilation due to other known causes or could not perform spirometry.

Results

The prevalence of OHS among SDB after excluding the other causes of hypoventilation was 15.87% (10/63). The predictors were determined using univariate analysis between daytime partial pressure of carbon dioxide (PaCO₂) and other predictors. PaCO₂ significantly correlated with minimum nocturnal oxygen saturation by pulse oximetry (SpO₂), FVC %predicted, BMI, daytime SpO₂, forced expiratory volume %predicted, and partial pressure of oxygen (PaO₂). Following a stepwise multiple regression, minimum nocturnal SpO₂, FVC %predicted, and BMI were found to be independent predictors of OHS. A minimum nocturnal SpO₂ threshold of 60%, FVC %predicted <74.5%, BMI >30.95 kg/m², and absolute FVC <2.33 L for men and <1.68 L for women were found to be predictors of OHS.

Conclusion

The prevalence of OHS in Indian patients is similar to Caucasians. OHS is seen in Indian patients even at a lower BMI and lower spirometric parameters.

Factors affecting spirometry reference range in growing children

OBJECTIVES

To find out the association of weight, height and age with spirometry variables and to generate a regression equation by taking weight as an independent variable beside age and height among children and adolescents of Karachi.

METHODS

A modified form of ISSAC questionnaire was used. The spirometry variables recorded were Forced vital capacity (FVC), Forced expiratory volume in 1 second (FEV1), FEV1/FVC, Peak expiratory flow rate (PEF), Forced expiratory flow between 25% and 75% expired volume (FEF25-75). A person's correlation coefficient among boys and girls were calculated for all spirometry variable considering age, height and weight as independent variables. The linear regression models were calculated.

RESULTS

The results reported a linear correlation of lung function variables with all three independent variables (i.e. p-value = 0.000), in which age and height manifested a strong positive correlation while weight reported a moderately significant correlation. All spirometry variables such as FVC, FEV1, PEF and FEF25-75 reported a significant coefficient of dependency and coefficient of correlation individually with age, height and weight.

CONCLUSION

It is concluded that beside age, height and weight both also have significant correlation with lung volumes so these should be taken into account when using spirometry as a diagnostic test.

Children with East Asian-Born Parents Have an Increased Risk of Allergy but May Not Have More Asthma in Early Childhood

BACKGROUND

We previously reported that infants with Asian-born parents are 3 times more likely to have IgE-mediated food allergy than those with Australian-born parents. It is unknown whether this translates to the increased risk of other allergic diseases later in childhood and whether ancestry interacts with other risk factors for allergic disease development.

OBJECTIVE

To compare prevalence and risk factors for allergic rhinitis, asthma, and aeroallergen sensitization at age 6 between children with East Asian-born and Caucasian-born parents.

METHODS

A total of 5276 1-year-old infants were recruited into a population-based longitudinal study of allergy. A total of 4455 children participated in age 6 follow-up (84.4%), including 3015 with Caucasian-born parents and 415 with East Asian-born parents. Children underwent skin prick tests to aeroallergens and questionnaires captured data on asthma, eczema, and allergic rhinitis.

RESULTS

Compared with children with Caucasian-born parents, children of East Asian-born parents had more allergic rhinitis (19.9% [95% confidence interval (CI) 14.9-26] vs 9.3% [95% CI 8-10.8], P < .001) and aeroallergen sensitization (64.3% [95% CI 57.5-70.5] vs 34.4% [95% CI 32.2-36.7], P < .001) at age 6. Asthma was similar in both groups (9.1% [95% CI 6.2-13.2] vs 11.7% [95% CI 10.4-13.1]), P = .21. Children with IgE-mediated food allergy and eczema in infancy were 3 times more likely to have asthma and 2 times more likely to have allergic rhinitis at age 6, irrespective of ancestry.

CONCLUSIONS

Children of East Asian ancestry born in Australia have a higher burden of most allergic diseases in the first 6 years of life, whereas asthma may follow a different pattern. IgE-mediated food allergy and eczema at age 1 increase the risk of asthma and allergic rhinitis irrespective of ancestry.

Global lung function initiative 2012 reference values for spirometry in Asian Americans

Background

Spirometry reference values specifically designed for Asian Americans are currently unavailable. The performance of Global Lung Function Initiative 2012 (GLI-2012) equations on assessing spirometry in Asian Americans has not been evaluated. This study aimed to assess the fitness of relevant GLI-2012 equations for spirometry in Asian Americans.

Methods

Asian subjects who never smoked and had qualified spirometry data were extracted from the National Health and Nutrition Examination Survey (NHANES) 2011–2012. Z-scores of forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), and FEV₁/FVC were separately constructed with GLI-2012 equations for North East (NE) Asians, South East (SE) Asians, and individuals of mixed ethnic origin (Mixed). In addition, Proportions of subjects with observed spirometry data below the lower limit of normal (LLN) were also evaluated on each GLI-2012 equation of interest.

Results

This study included 567 subjects (250 men and 317 women) aged 6–79 years. Spirometry z-scores (z-FEV₁, z-FVC, and z-FEV₁/FVC) based on GLI-2012 Mixed equations had mean values close to zero (− 0.278 to − 0.057) and standard deviations close to one (1.001 to 1.128); additionally, 6.0% (95% confidence interval (CI) 3.1–8.9%) and 6.4% (95% CI 3.7–9.1%) of subjects were with observed data below LLN for FEV₁/FVC in men and women, respectively. In contrast, for NE Asian equations, all mean values of z-FEV₁ and z-FVC were smaller than − 0.5; for SE Asian equations, mean values of z-FEV₁/FVC were significantly smaller than zero in men (− 0.333) and women (− 0.440).

Conclusions

GLI-2012 equations for individuals of mixed ethnic origin adequately fitted spirometry data in this sample of Asian Americans. Future studies with larger sample sizes are needed to confirm these findings.

Electronic supplementary material

The online version of this article (10.1186/s12890-018-0658-9) contains supplementary material, which is available to authorized users.

Collating Spirometry reference values in Asian children and Adolescents; puzzle out the reasons for variations

Lung function tests are essential for the diagnosis and management of different respiratory tract diseases; among them the spirometry is the gold standard technique. The accurate diagnosis, management and monitoring require proper interpretation of the results which depends upon the availability of spirometry reference data for that particular region to differentiate the diseased condition from the normal ones. Multiple studies had been done to find out their own area specific reference ranges but it is still lacking. This need was fulfilled by the Global Lung Function Initiative (GLI) in 2012, which reported the first global spirometry equation for all of the age groups. But some of the studies reported difference among GLI reference range and the measured range for that particular region. So here is the review of the reference ranges among 35,603 Asian children and adolescents from the 32 studies done specifically in Asia. The aim was to compare them with the study done by GLI team, along with these, tried to rule out the causal factor that are responsible for the variations in the reference ranges among the children and adolescents of different population. The literature was searched by using Google scholar and PubMed during the month of March up to July 2017. The review of all the articles published in Asia, specifically accounting for normal reference ranges in children and adolescent exhibit a wide variation among the reference ranges. This also suggest involvement of multiple modifiable and non-modifiable risk factors. So it's necessary to update the reference ranges for spirometry and its prediction equation as well.

Evaluation of the Global Lung Initiative 2012 Reference Values for Spirometry in African Children

RATIONALE

Despite the high burden of respiratory disease, no spirometry reference values for African children are available.

OBJECTIVES

Investigate whether the Global Lung Initiative (GLI-2012) reference values for spirometry are appropriate for children in sub-Saharan Africa and assess the impact of malnutrition on lung function.

METHODS

Anthropometry and spirometry were obtained in children aged 6 to 12 years from urban and semiurban schools in three African countries. Spirometry z-scores were derived using the GLI-2012 prediction equations for African Americans. Thinness (body mass index z-score < -2) was a surrogate for malnutrition. Spirometry outcomes were compared with those of African American children from the third National Health and Nutrition Survey.

MEASUREMENTS AND MAIN RESULTS

Spirometry data were analyzed from 1,082 schoolchildren (51% boys) aged 6.0 to 12.8 years in Angola (n = 306), Democratic Republic of the Congo (n = 377), and Madagascar (n = 399). GLI-2012 provided a good fit with mean (SD) z-scores of -0.11 (0.83) for FEV₁, -0.08 (0.86) for FVC, and -0.07 (0.83) for FEV₁/FVC. Because of low scatter, the fifth centile corresponded to -1.3 z-scores in boys and -1.5 z-scores in girls. Malnourished African children had a normal FEV₁/FVC ratio but significant reductions of ∼0.5 z-scores (∼5%) in FEV₁ and FVC compared with African American peers from the third National Health and Nutrition Survey. Children in Angola had the lowest, and those in Madagascar had the highest, zFEV₁ and zFVC.

CONCLUSIONS

The results of this study support the use of GLI-2012 reference values for schoolchildren in sub-Saharan Africa. Malnutrition affects body growth, leading to a proportionately smaller FEV₁ and FVC without respiratory impairment, as shown by the normal FEV₁/FVC ratio.

Explaining ethnic disparities in lung function among young adults: A pilot investigation

Background

Ethnic disparities in lung function have been linked mainly to anthropometric factors but have not been fully explained. We conducted a cross-sectional pilot study to investigate how best to study ethnic differences in lung function in young adults and evaluate whether these could be explained by birth weight and socio-economic factors.

Methods

We recruited 112 university students of White and South Asian British ethnicity, measured post-bronchodilator lung function, obtained information on respiratory symptoms and socio-economic factors through questionnaires, and acquired birth weight through data linkage. We regressed lung function against ethnicity and candidate predictors defined a priori using linear regression, and used penalised regression to examine a wider range of factors. We reviewed the implications of our findings for the feasibility of a larger study.

Results

There was a similar parental socio-economic environment and no difference in birth weight between the two ethnic groups, but the ethnic difference in FVC adjusted for sex, age, height, demi-span, father’s occupation, birth weight, maternal educational attainment and maternal upbringing was 0.81L (95%CI: -1.01 to -0.54L). Difference in body proportions did not explain the ethnic differences although parental immigration was an important predictor of FVC independent of ethnic group. Participants were comfortable with study procedures and we were able to link birth weight data to clinical measurements.

Conclusion

Studies of ethnic disparities in lung function among young adults are feasible. Future studies should recruit a socially more diverse sample and investigate the role of markers of acculturation in explaining such differences.

Challenges in Collating Spirometry Reference Data for South-Asian Children: An Observational Study

Availability of sophisticated statistical modelling for developing robust reference equations has improved interpretation of lung function results. In 2012, the Global Lung function Initiative(GLI) published the first global all-age, multi-ethnic reference equations for spirometry but these lacked equations for those originating from the Indian subcontinent (South-Asians). The aims of this study were to assess the extent to which existing GLI-ethnic adjustments might fit South-Asian paediatric spirometry data, assess any similarities and discrepancies between South-Asian datasets and explore the feasibility of deriving a suitable South-Asian GLI-adjustment.

Lung function in children in relation to ethnicity, physique and socioeconomic factors

Can ethnic differences in spirometry be attributed to differences in physique and socioeconomic factors?Assessments were undertaken in 2171 London primary schoolchildren on two occasions 1 year apart, whenever possible, as part of the Size and Lung function In Children (SLIC) study. Measurements included spirometry, detailed anthropometry, three-dimensional photonic scanning for regional body shape, body composition, information on ethnic ancestry, birth and respiratory history, socioeconomic circumstances, and tobacco smoke exposure.Technically acceptable spirometry was obtained from 1901 children (mean (range) age 8.3 (5.2-11.8) years, 46% boys, 35% White, 29% Black-African origin, 24% South-Asian, 12% Other/mixed) on 2767 test occasions. After adjusting for sex, age and height, forced expiratory volume in 1 s was 1.32, 0.89 and 0.51 z-score units lower in Black-African origin, South-Asian and Other/mixed ethnicity children, respectively, when compared with White children, with similar decrements for forced vital capacity (p<0.001 for all). Although further adjustment for sitting height and chest width reduced differences attributable to ethnicity by up to 16%, significant differences persisted after adjusting for all potential determinants, including socioeconomic circumstances.Ethnic differences in spirometric lung function persist despite adjusting for a wide range of potential determinants, including body physique and socioeconomic circumstances, emphasising the need to use ethnic-specific equations when interpreting results.

"Attacks" or "Whistling": Impact of Questionnaire Wording on Wheeze Prevalence Estimates

Background

Estimates of prevalence of wheeze depend on questionnaires. However, wording of questions may vary between studies. We investigated effects of alternative wording on estimates of prevalence and severity of wheeze, and associations with risk factors.

Methods

White and South Asian children from a population-based cohort (UK) were randomly assigned to two groups and followed up at one, four and six years (1998, 2001, 2003). Parents were asked either if their child ever had “attacks of wheeze” (attack group, N=535), or “wheezing or whistling in the chest” (whistling group, N=2859). All other study aspects were identical, including questions about other respiratory symptoms.

Results

Prevalence of wheeze ever was lower in the attack group than in the whistling group for all surveys (32 vs. 40% in white children aged one year, p<0.001). Prevalence of other respiratory symptoms did not differ between groups. Wheeze tended to be more severe in the attack group. The strength of association with risk factors was comparable in the two groups.

Conclusions

The wording of questions on wheeze can affect estimates of prevalence, but has less impact on measured associations with risk factors. Question wording is a potential source of between-study-heterogeneity in meta-analyses.

Specific airway resistance in healthy young Vietnamese and Caucasian adults

In healthy Vietnamese children the respiratory resistance has been suggested to be similar at 110 cm height but larger at 130 cm when compared with data in Caucasians from the literature, suggesting smaller airways in older Vietnamese children (Vu et al., 2008). The hypothesis tested here is whether the difference in airway resistance remains consistent throughout growth, and if it is larger in adult Vietnamese than in Caucasians. Airway resistance and Functional Residual Capacity were measured in healthy young Caucasian and Vietnamese adults in their respective native country using identical equipment and protocols. Ninety five subjects in Vietnam (60 males) and 101 in France (41 males) were recruited. Airway resistance was significantly larger in Vietnamese than in Caucasians and in females than in males, consistent with difference in body dimensions. Specific airway resistance however was not different by ethnicity or gender. The findings do not support the hypothesis that airway size at adult age - once normalized for lung volume - differs between Vietnamese and Caucasians.

Disparities in pulmonary function in healthy children across the Indian urban-rural continuum

RATIONALE

Marked socioeconomic health-care disparities are recognized in India, but lung health inequalities between urban and rural children have not been studied.

OBJECTIVES

We investigated whether differences exist in spirometric pulmonary function in healthy children across the Indian urban-rural continuum and compared results with those from Indian children living in the UK.

METHODS

Indian children aged 5 to 12 years were recruited from Indian urban, semiurban, and rural schools, and as part of the Size and Lung Function in Children study, London. Anthropometric and spirometric assessments were undertaken.

MEASUREMENTS AND MAIN RESULTS

Acceptable spirometric data were obtained from 728 (58% boys) children in India and 311 (50% boys) UK-Indian children. As an entire group, the India-resident children had significantly lower z FEV1 and z FVC than UK-Indian children (P < 0.0005), when expressed using Global Lung Function Initiative-2012 equations. However, when India-resident children were categorized according to residence, there were no differences in z FEV1 and z FVC between Indian-urban and UK-Indian children. There were, however, significant reductions of ∼ 0.5 z scores and 0.9 z scores in both FEV1 and FVC (with no difference in FEV1/FVC) in Indian-semiurban and Indian-rural children, respectively, when compared with Indian-urban children (P < 0.0005). z Body mass index, socioeconomic circumstances, tobacco, and biomass exposure were individually significantly associated with z FEV1 and z FVC (P < 0.0005).

CONCLUSIONS

The presence of an urban-rural continuum of lung function within a specific ethnic group emphasizes the impact of environmental factors on lung growth in emerging nations such as India, which must be taken into account when developing ethnic-specific reference values or designing studies to optimize lung health.

Lung function testing in children: importance of race and ethnic-specific reference equations

Marked differences in lung function occur between children of different racial and ethnic backgrounds even when all known confounders including socioeconomic circumstances have been taken into account. Use of ethnic-specific equations, such as those recently published by the Global Lung Function Initiative, help to minimize such differences, thereby improving the accuracy with which lung disease can be identified and treated during childhood, as well as enabling the true impact of adverse environmental or socioeconomic exposures to be assessed, irrespective of ethnic background. In future, incorporation of ancestry and, within emerging nations undergoing secular changes in anthropometry, sitting height, into normative equations may further improve the accuracy of predicting lung function and hence assessment of disease severity within any given individual.

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.

Copy number variation of the beta-defensin genes in europeans: no supporting evidence for association with lung function, chronic obstructive pulmonary disease or asthma

Lung function measures are heritable, predict mortality and are relevant in diagnosis of chronic obstructive pulmonary disease (COPD). COPD and asthma are diseases of the airways with major public health impacts and each have a heritable component. Genome-wide association studies of SNPs have revealed novel genetic associations with both diseases but only account for a small proportion of the heritability. Complex copy number variation may account for some of the missing heritability. A well-characterised genomic region of complex copy number variation contains beta-defensin genes (DEFB103, DEFB104 and DEFB4), which have a role in the innate immune response. Previous studies have implicated these and related genes as being associated with asthma or COPD. We hypothesised that copy number variation of these genes may play a role in lung function in the general population and in COPD and asthma risk. We undertook copy number typing of this locus in 1149 adult and 689 children using a paralogue ratio test and investigated association with COPD, asthma and lung function. Replication of findings was assessed in a larger independent sample of COPD cases and smoking controls. We found evidence for an association of beta-defensin copy number with COPD in the adult cohort (OR = 1.4, 95%CI:1.02-1.92, P = 0.039) but this finding, and findings from a previous study, were not replicated in a larger follow-up sample(OR = 0.89, 95%CI:0.72-1.07, P = 0.217). No robust evidence of association with asthma in children was observed. We found no evidence for association between beta-defensin copy number and lung function in the general populations. Our findings suggest that previous reports of association of beta-defensin copy number with COPD should be viewed with caution. Suboptimal measurement of copy number can lead to spurious associations. Further beta-defensin copy number measurement in larger sample sizes of COPD cases and children with asthma are needed.