The use of the lower limit of normal as a criterion for COPD excludes patients with increased morbidity and high consumption of health-care resources.

The objective of this study is to analyze the clinical characteristics of two COPD patient populations: one diagnosed using the lower limit of normal (LLN) and another diagnosed by the GOLD criteria. We also compared the population excluded by the LLN criterion with a non-COPD control population. The COPD patients determined with the LLN criterion presented significantly lower levels of FEV1/FVC at 0.55 (0.8) vs. 0.66 (0.2), P=.000; FEV1 44.9% (14) vs. 53.8% (13), P=.000, and FVC 64.7% (17) vs. 70.4% p 0.04. The two COPD groups presented more frequent ER visits in the last year (57% and 52% of the patients, respectively, compared with 11.9% of the control group), without any statistically significant differences between the two. This same pattern was observed in the number of ER visits in the last year: 1.98 (1.6), 1.84 (1.5) and 1.18 (0.7), respectively. When we analyzed the prevalence of the comorbidities that are most frequently associated COPD, there was a clear increase in the percentage of patients who presented associated disorders compared with the control group. Nevertheless, these differences were not very relevant between the two COPD groups. The differences also were not relevant between both COPD groups in the pharmacological prescription profile. In conclusion, the use of the LLN as a criterion for establishing the diagnosis of COPD, compared with the GOLD criteria, excludes a population with important clinical manifestations and with a high consumption of health-care resources. Before its implementation, the relevance of applying this criterion in clinical practice should be analyzed.