Comparison of the "Fixed thresholds" and the "Z-Score" for Spirometric diagnosis of Asthma
Pneumology Department, Arrazi Hospital, Chu Mohammed VI, LRMS, FMPM UCA, Marrakesh Morocco.
Research Article
World Journal of Advanced Research and Reviews, 2023, 19(01), 1017–1021
Article DOI: 10.30574/wjarr.2023.19.1.1447
Publication history:
Received on 08 June 2023; revised on 17 July 2023; accepted on 19 July 2023
Abstract:
Introduction and objective: The use of z-score to interpret lung function has been recommended by GLI 2012 [1] and ATS/ERS 2022 [2], with evidence of false positives in the diagnosis of asthma when using fixed thresholds of FEV1/FVC. The aim of our study is to analyze the pulmonary function tests (PFTs) of patients admitted to our explorations for suspected asthma according to the z-score and the fixed thresholds, with a comparison of the two methods.
Methods: Our study is retrospective, carried out over a one-year period, from February 2022 to February 2023.
Results: We collected 292 cases. The average age of patients was 30 years, with a clear predominance of women (65%).
A similarity of results according to the fixed thresholds and z-score was found in 235 cases (182 had a normal PFT and 53 had an OVD). An OVD was found in 39 cases according to the fixed thresholds, whereas PFT was normal according to the z-score. A reduction of FVC according to the z-score, while the PFT was normal to the fixed thresholds, was noted in 18 cases. It was related to a hyperinflation
In our study, using the z-score, we found 39 cases of false-positive spirometric diagnosis of asthma and under-diagnosis of reduction of FVC in 18 cases.
Conclusion: The prevalence of asthma based on spirometry is higher when using the fixed thresholds than when using the z-score, hence the need for standardization of interpretation methods, notably by GINA 2024.
Keywords:
Pulmonary Function Tests; Z-Score; Asthma; Spirometry; Airway Obstruction
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