Role of the lower limit of normal in COPD diagnosis.

Abstract

Introduction: According to GOLD, the diagnosis of chronic obstructive pulmonary disease (COPD) requires an FEV1/FVC ratio of less than 0.7. Another method that has been proposed is the use of the lower limit of normal (LLN), which represents the 5th percentile of the FEV1/FVC ratio of a healthy reference population.

Methods: The following variables were analyzed in a cohort of 59 patients diagnosed with COPD during 2021: sex, age, height, weight, BMI, cardiac comorbidities, grade of dyspnea (mMRC), number of exacerbations and admissions in the last year, FEV1, KCO and RV/TLC. They were classified into two groups: group A with an FEV1/FVC <0.7 and ≤LIN coinciding diagnosis by both methods and group B with an FEV1/FVC <0.7 but >LIN, with discordant diagnoses. The purpose of this study was to compare the characteristics of both groups.

Results: The mean age of the patients was 70.6 ± 7.80 years, 59.3% being male. They had a mean BMI of 28 and 19 (32.2%) were active smokers. 50 patients were classified in group A (84.7%) and 9 patients in group B (15.3%). There were no significant differences in terms of sex, anthropometric variables, exacerbations or grade of dyspnea. All patients in group B were older than 65 years, had a lower RV/TLC ratio and higher KCO than group A. Regarding to group A, the mean FEV1% was 52.8 ± 17.7, while in group B it was 77.0 ± 11.2, revealing statistically significant differences.

Conclusions: Patients in group B (not diagnosed with COPD by LIN) had better pulmonary function, nevertheless, they presented clinical manifestations and resource consumption similar to group A, so that the use of LIN as the only diagnostic criterion excludes excludes a large number of patients that require treatment and follow-up.