Health status and prognosis of COPD patients in relation to the FEV₁/FVC ratio

Whether COPD should be diagnosed using the lower limit of normal (LLN) or a fixed FEV₁/FVC ratio <0.70 (FR) is debated. We compared symptom and disease burden in COPD patients with FEV₁/FVC below both thresholds (FR + /LLN + ) versus those between them (FR + /LLN-). This cohort study included 572 COPD patients from primary and secondary care in the central Swedish regions of Dalarna, Gävleborg, and Uppsala. FR + /LLN + COPD patients with FEV₁ ≥ 60% predicted (n = 194) was compared to FR + /LLN- COPD patients (n = 85) in order to have similar FEV₁ levels in both groups. The symptom burden was assessed using the modified British Medical Research Council scale of dyspnoea (mMRC), the COPD Assessment Test (CAT), and the Clinical COPD Questionnaire (CCQ). The disease burden was assessed by exacerbations and hospital admissions over the subsequent three years. The 279 studied patients (57% females) had a mean age of 68.2 years and a mean FEV₁% predicted of 73.0%. The FR + /LLN+ group had comparable clinical characteristics to the FR + /LLN- group regarding FEV₁% predicted (72.5 vs 74.2%), use of inhaled medicines (76.3 vs 76.5%), and previous exacerbations (23.2 vs 18.8%), all p-values > 0.05. Moreover, comparable prevalence of exacerbations and hospital admissions were found during the subsequent three years (31.7 vs 37.7%, and 4.8 vs 2.6%, respectively, all p-values > 0.05). Symptom burden was comparable for mMRC and CCQ, but the FR + /LLN- group had a higher CAT score than the FR + /LLN+ group (10.6 vs 12.6, p = 0.038), a finding also confirmed in adjusted analyses. FR + /LLN+ and FR + /LLN- COPD patients had relatively comparable symptom and disease burden, suggesting that not meeting the LLN criteria does not indicate a milder disease in clinically diagnosed COPD with comparable FEV₁.