Influences of Two FEV₁ Reference Equations (GLI-2012 and GIRH-2017) on Airflow Limitation Classification Among COPD Patients

Abstract

Objective

To explore the clinical effects of different forced expiratory volume in 1s (FEV₁) reference equations on chronic obstructive pulmonary disease (COPD) airflow limitation (AFL) classification.

Methods

We conducted a COPD screening program for residents over 40 years old from 2019 to 2021. All residents received the COPD screening questionnaire (COPD-SQ) and spirometry. Postbronchodilator FEV₁/FVC (forced vital capacity) <0.7 was used as the diagnostic criterion of COPD and two reference equations of FEV₁ predicted values were used for AFL severity classification: the European Respiratory Society Global Lung Function Initiative reference equation in 2012 (GLI-2012) and the Guangzhou Institute of Respiratory Health reference equation in 2017 (GIRH-2017). Clinical characteristics of patients in GOLD (Global Initiative for Chronic Obstructive Pulmonary Disease) 1–4 grades classified by the two reference equations were compared.

Results

Among 3524 participants, 659 subjects obtained a COPD-SQ score of 16 or more and 743 participants were found to have AFL. The COPD-SQ showed high sensitivity (59%) and specificity (91%) in primary COPD screening. Great differences in COPD severity classification were found when applying the two equations (p < 0.001). Compared with GIRH-2017, patients with AFL classified by GLI-2012 equations were significantly severer. The relationship between symptom scores, acute exacerbation (AE) history distributions and COPD severities classified by the two equations showed a consistent trend of positive but weak correlation. Group A, B, C and D existed in all GOLD 1 to 3 COPD patients, but in GOLD 4, only Groups B and D existed. However, no clear significant differences were found in symptoms, AE risk assessments, risk factors exposure and even the combined ABCD grouping under the two equations.

Conclusion

There were significant differences in COPD AFL severity classification with GLI-2012 and GIRH-2017 FEV₁ reference equations. But these severity estimation differences did not affect symptoms, AE risk assessments and ABCD grouping of patients at all GOLD grades.

Keywords:

• COPD
• airflow limitation
• FEV₁%pred
• symptoms assessment
• acute exacerbation

Abbreviations

AEs, acute exacerbations; AFL, airflow limitation; BOLD, Burden of Obstructive Lung Diseases; BMI, body mass index; COPD-SQ, COPD screening questionnaire; CAT, COPD Assessment Test; COPD, chronic obstructive pulmonary disease; CCQ, COPD Clinical Questionnaire; China-2002, the China revised reference equation in 2002; COVID-19, coronavirus disease in 2019; 95% CI, 95% confidence interval; ECSC, European Coal and Steel Community; ERS, European Respiratory Society; FEV1, Forced expiratory volume in 1 s; FVC, forced vital capacity; GOLD, Global initiative for chronic obstructive pulmonary disease; GLI, Global Lung Function Initiative; GIRH, Guangzhou Institute of Respiratory Health; LLN, Lower Limit of Normal; SD, Standard deviation; mMRC, the modified British Medical Research Council.

Clinical Trial Registration

Registrar: Liu Sha

Website: http://www.chictr.org.cn

Clinical trial registration Number: ChiCTR1900026502.

Data Sharing Statement

Please contact author for data requests.

Ethics Approval and Consent to Participate

All the participants were made fully aware of the purpose of study, and all participants gave informed consent. The Medical Ethics Committee, University of South China approved the study.

Consent for Publication

All participants have signed consent for publishing their personal data for scientific research. DFW and YW contributed equally to the article.

Acknowledgments

The study was funded by National Natural Science Foundation of China (81900044, to Dr. S. Liu), Natural Science Foundation of Hunan Province (2021JJ40484, to Dr. S. Liu), The Key project of Science and Technology Plan of Health Commission of Hunan Province (20201922, to Prof. X. Tan).

Disclosure

All authors declare that there is no conflict of interest in the publication.