Renewed Japanese spirometric reference variables and risk stratification for postoperative outcomes in COPD patients with resected lung cancer

Although the lower limit of normal (LLN) of FEV1/FVC detects at-risk patients for postoperative outcomes among Japanese chronic obstructive pulmonary disease (COPD) patients with resected lung cancer, there was a lack of a Japanese reference equation to calculate the LLN of FEV1/FVC. Renewed Japanese spirometric reference variables might enable us to verify clinical impact of the LLN of FEV1/FVC among the Japanese population. To evaluate the clinical impact of the LLN of FEV1/FVC by using this renewed reference, data were retrospectively analyzed from 609 newly diagnosed lung cancer patients who had undergone thoracic surgery between 2006 and 2011. The combined assessment of the 0.70 fixed ratio and the LLN of the FEV1/FVC ratio classified the 609 subjects into the COPD (214 subjects), non-COPD (337 subjects), and in-between (58 subjects) groups, respectively. All of the relative odds ratios (ORs) of postoperative outcomes for the comparison between the in-between and non-COPD groups did not show significant confidence intervals (CIs). On the other hand, the adjusted ORs of postoperative outcomes for the COPD group versus the non-COPD group were 2.840 (95% CI: 1.824–4.421) for prolonged oxygen therapy (POT), 1.836 (95% CI: 1.166–2.890) for prolonged postoperative stays, and 1.637 (95% CI: 1.007–2.663) for combined complications. Adjusted comparisons of POT between the in-between and COPD groups also showed a significant relative OR of 2.984 (95% CI: 1.447–6.153). A standardized assessment of the LLN of FEV1/FVC by a renewed Japanese spirometric reference provides risk stratification for postoperative outcomes in the population.