History- and symptom-based prediction of pulmonary function and the presence of chronic obstructive pulmonary disease: development and validation of a nomogram

Background: Early suspicion followed by assessing lung function with spirometry could decrease the underdiagnosis of chronic obstructive pulmonary disease (COPD) in primary care. We aimed to develop a nomogram to predict the FEV1/FVC ratio and the presence of COPD.Methods: We retrospectively reviewed data of 4,241 adult patients who underwent spirometry between 2013 and 2019. By linear regression analysis, variables associated with FEV1/FVC were identified in the training cohort (n=2,969). Using the variables as predictors, a nomogram was created to predict the FEV1/FVC ratio and validated in the test cohort (n=1,272).Results: Older age (Odds ratio [OR], 0.858; 95% confidence interval [CI], 0.833-0.885), male sex (OR, 0.149; 95% CI, 0.064–0.348), current or past smoking history (OR, 0.036; 95% CI, 0.015–0.086), the presence of dyspnea (OR, 0.086; 95% CI, 0.027–0.275), and the absence of overweight (OR, 2.445; 95% CI, 1.210–4.942) were significantly associated with the FEV1/FVC ratio. In the final testing, the developed nomogram showed a mean absolute error of 0.822 (95% CI, 0.789–0.854) between the predicted and actual FEV1/FVC ratios. The overall performance was best when FEV1/FVC < 70% was used as a diagnostic criterion for COPD; the sensitivity, specificity, and balanced accuracy were 82.3%, 68.6%, and 75.5%, respectively.Conclusion: The developed nomogram could be used to identify potential patients at risk of COPD who may need further evaluation, especially in the primary care setting where spirometry is not available.