Association of FeNO Decline Rate with Symptom Improvement in COPD: A Real-World Observational Study.

BACKGROUND: The association between relative changes in fractional exhaled nitric oxide (FeNO) in chronic obstructive pulmonary disease (COPD) with patient-reported symptoms improvements remains uncertain.

OBJECTIVE: To assess the association of the rate of FeNO decline with the achievement of the minimum clinically important difference (MCID) in COPD Assessment Test (CAT) score.

METHODS: We conducted a single-center, retrospective real-world study involving 111 adults with COPD. Patients were classified into two groups: those with symptom improvement (CAT decline ≥2 points) and those with no improvement (CAT decline <2 points). Logistic regression evaluated associations between FeNO decline rate and CAT MCID, adjusting for clinically relevant covariates. Receiver operating characteristic (ROC) curve analysis estimated the discriminatory performances of it.

RESULTS: Of 111 patients, 53 (47.7%) achieved the CAT MCID. Multivariate logistic regression found that the rate of FeNO decline was independently associated with symptom improvement (adjusted OR 2.08, 95% CI 1.01-4.29, P=0.047). Baseline CAT also showed association with symptom improvement (adjusted OR 1.06, 95% CI 1.00-1.12, P=0.034). BMI showed a positive trend but without statistical significance (adjusted OR 1.13, 95% CI 1.00-1.29, P=0.056). AUC of FeNO decline rate, baseline CAT, combined with BMI in discriminating CAT MCID were 0.713 (95% CI 0.617, 0.809).

CONCLUSION: The rate of FeNO decline was significantly associated with clinically meaningful CAT improvement in this study, which indicated dynamic measures of type-2 inflammation can complement blood eosinophil counts to refine phenotyping and inform precision management in COPD.