An examination of factorial invariance of the Asthma Control Questionnaire among adults with severe asthma

Ronald Mc Dowell, Liam Heaney, Thomas Brown, B Bunting, Hassan Burhan, Rekha Chaudhuri, Paddy Dennison, Shoaib Faruqi, Robin Gore, David Jackson, Andrew Menzies-gow, Thomas Pantin, Mitesh Patel, Paul Pfeffer, Salman Siddiqui, John Busby

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The Asthma Control Questionnaire (ACQ) is used to assess asthma symptom control. The relationship between the questionnaire items and symptom control has not been fully studied in severe asthmatic patients, and its validity for making comparisons between subgroups of patients is unknown.

Data was obtained from patients in the United Kingdom Severe Asthma Registry whose symptom control was assessed using the five-item ACQ (ACQ5) (n = 2,951). Confirmatory factor analysis determined whether a latent factor for asthma symptom control, as measured by the ACQ5, was consistent with the data. Measurement invariance was examined in relation to ethnicity, sex
and age; this included testing for approximate measurement invariance using Bayesian Structural Equation Modelling (BSEM). The fitted models were used to estimate the internal consistency reliability of the ACQ5. Invariance of factor means across subgroups was assessed.

A one-factor construct with residual correlations for the ACQ5 was an excellent fit to the data in all subgroups (Root Mean Square Error Approximation 0.03 [90%CI 0.02,0.05], p close fit 0.93, Comparative Fit Index 1.00, Tucker Lewis Index 1.00}. Expected item responses were consistent for Caucasian and non-Caucasian patients with the same absolute level of symptom control. There was some evidence that females and younger adults reported wakening more frequently during the night than males and older adults respectively
with the same absolute level of symptom control (p<0.001). However approximate measurement invariance was tenable and any failure to observe strong measurement invariance had minimal impact when comparing mean levels of asthma symptom control between patients of different sexes or ages. Average levels of asthma symptom control were lower for non-Caucasians (p = 0.001), females (p<0.01)and increased with age (p<0.01). Reliability of the
instrument was high (over 88%) in all subgroups studied.

The ACQ5 is informative in comparing levels of symptom control between severe asthmatic patients of different ethnicities, sexes and ages. It is important that analyses are replicated in other severe asthma registries to determine whether measurement invariance is observed.
Original languageEnglish
Article numbere0295493
Pages (from-to)1-17
Number of pages17
JournalPLoS ONE
Issue number12
Publication statusPublished (in print/issue) - 7 Dec 2023

Bibliographical note

Funding Information:
JB was awarded Grant NICHS 2020_C01 by Northern Ireland Chest Heart & Stroke Association ( The funder provided support in the form of salaries for RMcD, but had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of authors are articulated in the 'Author Contributions' section.

Publisher Copyright:
© 2023 McDowell et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


  • Male
  • Female
  • Humans
  • Aged
  • Reproducibility of Results
  • Bayes Theorem
  • Psychometrics
  • Surveys and Questionnaires
  • Asthma/diagnosis


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