Fixed Ratio versus Lower Limit of Normality for Diagnosing COPD in Primary Care: Long-Term Follow-Up of EGARPOC Study
Received 21 February 2020
Accepted for publication 24 May 2020
Published 18 June 2020 Volume 2020:15 Pages 1403—1413
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 5
Editor who approved publication: Dr Richard Russell
Montserrat Llordés, 1 Angeles Jaen, 2 Elba Zurdo, 1 Montserrat Roca, 1 Inmaculada Vazquez, 1 Pere Almagro 3 On behalf of the EGARPOC collaboration group
1Terrassa Sud Primary Care Center, Hospital Universitari Mutua Terrassa, University of Barcelona, Barcelona, Spain; 2Fundació Docència i Recerca Mutua Terrassa, Barcelona, Spain; 3Internal Medicine Service, Hospital Universitari Mutua Terrassa, University of Barcelona, Barcelona, Spain
Correspondence: Montserrat Llordés
Terrassa Sud Primary Care Center, Hospital Universitari Mutua Terrassa, Avenida Santa Eulalia s/n, Terrassa, Barcelona 08223, Spain
Tel +34 93 785 51 61
Fax +34 93 731 49 52
Purpose: The best criterion for diagnosing airway obstruction in COPD, fixed ratio (FR: FEV1/FVC< 0.7) or lower limit of normality (LLN), remains controversial. We compared the long-term evolution of COPD patients according to the initial obstruction criteria.
Patients and Methods: Between 2005 and 2008, we evaluated 1728 subjects over 45 years of age with smoking history, pertaining to a primary care center. A total of 424 patients were obstructive by FR, after a bronchodilator test. Of those, 289 patients met obstruction criteria for both FR and LLN and were considered concordant patients (FR+LLN+), while 135 patients were obstructive by FR but non-obstructive by LLN and were defined as discordant patients (FR+LLN-).
Results: Forty-eight patients (11.3%) were lost in follow-up, and 158 died (37.3%). After a median time of 120.4 months (IQR 25– 75%: 110.2– 128.8), 215 patients were spirometrically reevaluated. The annualized loss of FEV1/FVC was greater in discordant (FR+LLN-) patients [0.54 (0.8) vs 0.82 (0.7); p = 0.008], while 81% became concordant (FR+LLN+) during the follow-up. Hospitalization for COPD exacerbations was more frequent in concordant (FR+LLN+) patients (1.57± 3.51 vs 0.77± 2.29; p = 0.002). Adjusting for age, concordant (FR+LLN+) patients had greater COPD mortality (HR: 2.97; CI 95%: 1.27– 7.3; p = 0.02).
Conclusion: LLN seems to be less useful for COPD diagnosis in primary care. Discordant (FR+LLN-) patients lost more FEV1/FVC during their evolution and tended to become concordant. LLN predicted COPD hospitalizations and mortality more poorly.
Keywords: COPD, lower limit of normality, fixed ratio, prognosis, airway obstruction, mortality
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