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Paediatric lung disease
Original research
Variability in forced expiratory volume in 1 s in children with symptomatically well-controlled asthma
  1. Nicole Filipow1,
  2. Stephen Turner2,3,
  3. Helen L Petsky4,
  4. Anne B Chang5,6,
  5. Thomas Frischer7,
  6. Stanley Szefler8,
  7. Francoise Vermeulen9,
  8. Sanja Stanojevic10
  1. 1Great Ormond Street Institute of Child Health, University College London, London, UK
  2. 2NHS Grampian, Aberdeen, UK
  3. 3Child Health, University of Aberdeen, Aberdeen, UK
  4. 4School of Nursing and Midwifery, Griffith University Menzies Health Institute, Nathan, Queensland, Australia
  5. 5Child Health Division, Menzies School of Health Research, Darwin, Northern Territory, Australia
  6. 6Queensland Children's Respiratory Centre, Royal Children's Hospital, Brisbane, Queensland, Australia
  7. 7Sigmund Freud Private University, Vienna, Austria
  8. 8Pediatrics, University of Colorado Denver School of Medicine, Aurora, Colorado, USA
  9. 9Department of Integrated Paediatrics, Université Libre de Bruxelles, Bruxelles, Belgium
  10. 10Community Health and Epidemiology, Dalhousie University, Halifax, Nova Scotia, Canada
  1. Correspondence to Dr Stephen Turner; s.w.turner{at}abdn.ac.uk

Abstract

Aims Spirometry is used by many clinicians to monitor asthma in children but relatively little is understood about its variability over time. The aim of this study was to determine the variability of forced expiratory volume in 1 s (FEV1) in children with symptomatically well-controlled asthma by applying three different methods of expressing change in FEV1 over 3-month intervals.

Methods Data from five longitudinal studies of children with asthma which measured FEV1 at 3-month intervals over 6 or 12 months were used. We analysed paired FEV1 measurements when asthma symptoms were controlled. The variability of FEV1% predicted (FEV1%), FEV1 z-score (FEV1z) and conditional z score for change (Zc) in FEV1 was expressed as limits of agreement.

Results A total of 881 children had 3338 FEV1 measurements on occasions when asthma was controlled; 5184 pairs of FEV1 measurements made at 3-month intervals were available. Each unit change in FEV1 z score was equivalent to a Zc 1.45 and an absolute change in FEV1% of 11.6%. The limits of agreement for change in FEV1% were −20 and +21, absolute change in FEV1 z were −1.7 and +1.7 and Zc were −2.6 and +2.1. Regression to the mean and increased variability in younger children were present for change in FEV1% and FEV1z comparisons, but not Zc.

Conclusion Given the wide limits of agreement of paired FEV1 measurements in symptomatically well-controlled children, asthma treatment should primarily be guided by symptoms and not by a change in spirometry.

  • Asthma
  • Child
  • Paediatric asthma

Data availability statement

Data may be obtained from a third party and are not publicly available. Original data may be obtained by contacting the lead for each of the five study populations whose data contributed to the present analysis.

https://doi.org/10.1136/thorax-2024-221755

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    Data availability statement

    Data may be obtained from a third party and are not publicly available. Original data may be obtained by contacting the lead for each of the five study populations whose data contributed to the present analysis.

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    Footnotes

    • X @sanjalovesdata

    • Contributors ST and SStanojevic conceived the idea. NF analysed the data. HLP, ABC, TF, SSzefler, FV and ST contributed data. All authors made contributions to the manuscript. ST is the guarantor for the work.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.