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. 2022 Mar 21;23(1):67.
doi: 10.1186/s12931-022-01990-2.

Spirometry parameters used to define small airways obstruction in population-based studies: systematic review

Ben Knox-Brown  1 , Octavia Mulhern  2 , Johanna Feary  2 , Andre F S Amaral  2
Affiliations

Spirometry parameters used to define small airways obstruction in population-based studies: systematic review

Ben Knox-Brown et al. Respir Res. .

Abstract

Background: The assessment of small airways obstruction (SAO) using spirometry is practiced in population-based studies. However, it is not clear what are the most used parameters and cut-offs to define abnormal results.

Methods: We searched three databases (Medline, Web of Science, Google Scholar) for population-based studies, published by 1 May 2021, that used spirometry parameters to identify SAO and/or provided criteria for defining SAO. We systematically reviewed these studies and summarised evidence to determine the most widely used spirometry parameter and criteria for defining SAO. In addition, we extracted prevalence estimates and identified associated risk factors. To estimate a pooled prevalence of SAO, we conducted a meta-analysis and explored heterogeneity across studies using meta regression.

Results: Twenty-five studies used spirometry to identify SAO. The most widely utilised parameter (15 studies) was FEF25-75, either alone or in combination with other measurements. Ten studies provided criteria for the definition of SAO, of which percent predicted cut-offs were the most common (5 studies). However, there was no agreement on which cut-off value to use. Prevalence of SAO ranged from 7.5% to 45.9%. As a result of high heterogeneity across studies (I2 = 99.3%), explained by choice of spirometry parameter and WHO region, we do not present a pooled prevalence estimate.

Conclusion: There is a lack of consensus regarding the best spirometry parameter or defining criteria for identification of SAO. The value of continuing to measure SAO using spirometry is unclear without further research using large longitudinal data. PROSPERO registration number CRD42021250206.

Keywords: Global; Physiology; Prevalence; Respiratory epidemiology; Small airways obstruction; Spirometry.

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Conflict of interest statement

None declared.

Figures

Fig. 1
Fig. 1
PRISMA flow diagram indicating study selection process
Fig. 2
Fig. 2
Spirometry parameters used to measure small airways obstruction in population-based studies. Other: Concavity index, FEF50/FEF25 and FET25–75
Fig. 3
Fig. 3
Prevalence of small airways obstruction, based on pre-bronchodilator spirometry, in nine studies
See this image and copyright information in PMC

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