Jisong Yan, Yinqi Ding, Minghui Shi, Xingyao Tang, Wei Li, Xu Chu, Tingting Huang, Yanan Cui, Zhoude Zheng, Yaodie Peng, Rui Su, Zehua Yang, Yong Li, Chunyu Zhang, Cunbo Jia, Zhengming Chen, Canqing Yu, Ke Huang, Ting Yang
A pre-BD FEV1/FVC threshold of 0.56 effectively "rules-in" COPD in primary care and identifies patients with poor prognosis. The alternative threshold of 0.62 offers a practical option to further reduce post-BD testing while maintaining an acceptable PPV. Both thresholds facilitate pragmatic triage and early diagnosis without routine post-BD testing.
BACKGROUND: Post-bronchodilator (BD) spirometry is underused in primary care settings, limiting COPD diagnosis. This study aimed to derive and validate pre-BD thresholds that safely rule in COPD and enable immediate diagnosis.
METHODS: We derived pre-BD FEV1/FVC thresholds using a nationally representative derivation dataset (CPHS, n = 6360 with pre-BD ratio <0.7), with cross-sectional external validation in the China Kadoorie Biobank (CKB, n = 1890) and longitudinal validation in a national screening cohort (NSC, n = 7620 with 1-year follow-up). The optimal threshold was selected based on positive predictive value (PPV) for post-BD FEV1/FVC <0.7. One-year longitudinal follow-up assessed diagnostic stability and prognostic value.
FINDINGS: A pre-BD threshold of 0.56 was identified, yielding a PPV of 0.953 (95% CI, 0.939-0.965) in derivation set and 0.919 (95% CI, 0.875-0.940) in the CKB validation set. In subgroups with higher prior probability (male, age >60 years, smoking, and with respiratory symptoms), the PPV was further increased. At one-year follow-up in the NSC, 86.9% of participants with baseline pre-BD <0.56 still met the post-BD COPD criteria. Patients below 0.56 had significantly higher risks of acute exacerbation (OR, 3.34; 95% CI, 2.55-4.37) and respiratory hospitalization (OR, 3.42; 95% CI, 2.65-4.42). An alternative threshold of 0.62 gave a PPV of 0.891 (95% CI, 0.866-0.913) in CKB and allowed 33.8%-49.0% of participants across cohorts to bypass post-BD testing.
INTERPRETATION: A pre-BD FEV1/FVC threshold of 0.56 effectively "rules-in" COPD in primary care and identifies patients with poor prognosis. The alternative threshold of 0.62 offers a practical option to further reduce post-BD testing while maintaining an acceptable PPV. Both thresholds facilitate pragmatic triage and early diagnosis without routine post-BD testing.
FUNDING: This work was funded by National High Level Hospital Clinical Research Funding (2025-NHLHCRF-JBGS-B-WZ-18), Noncommunicable Chronic Diseases-National Science and Technology Major Project (2023ZD0506003, 2023ZD0506306, 2023ZD0510101, 2023ZD0510100), Social Development Project of Yunnan Province (202403AC100006) and Beijing Nova Program (20250484849).