Spirometric Thresholds for Diagnosing COPD: 0.70 or LLN, Pre- or Post-dilator Values?

In absence of a gold standard for chronic obstructive pulmonary disease (COPD) it remains difficult to compare the true diagnostic characteristics of the forced expiratory volume in 1 second to the forced vital capacity (FEV1/FVC) 50, consulting for persistent cough, but without physician-diagnosed COPD, were prospectively enrolled. All underwent extensive history taking, physical examination, spirometry and diffusion testing. An expert panel, including a board certified respiratory physician, assessed all diagnostic information to determine the presence or absence of COPD and served as reference standard. Then, 104 participants were diagnosed with COPD by the panel. The reproducibility of the panel diagnosis was high (kappa of 0.94). Sensitivity estimates of <0.70 were significantly higher than that of <LLN (0.73 and 0.47, respectively, p < 0.001). The fixed approach was less specific than the LLN (0.95 and 0.99, respectively, p < 0.001). There was no significant difference in diagnostic property when using pre- or post-bronchodilator FEV1/FVC (p = 0.615). In a symptomatic primary care population, the FEV1/FVC <0.70 was more accurate to detect COPD.