Reliability of Pulmonary Function Tests in Patients with Chronic Obstructive Pulmonary Disease

INTRODUCTION: Chronic Obstructive Pulmonary Disease (COPD) is frequently underdiagnosed due to limited use and suboptimal quality of spirometry.

METHODS: This multicenter, prospective observational study aimed to assess the quality of spirometry tests in COPD patients across six tertiary care centers in Turkey. A total of 560 spirometry tests were independently evaluated by two pulmonologists, and inter-rater reliability was analyzed using Cohen's Kappa.

RESULTS: The study included 124 women and 436 men, with a mean age of 65.9±10.2 years. Spirometry patterns were interpreted as obstructive in 79.1% of tests, restrictive in 5.7%, mixed in 2.7%, normal in 6.7%, inconclusive in 5.5%, and as upper airway obstruction in 0.18% of cases (=0.890). Routine post-bronchodilator testing was performed in 87.14% of the cases, while 12.85% were post-reversibility tests. Graphical data included volume-time curves (88.5%), flow-volume loops (99.6%), and inspiratory limbs (98.7%). Reference values were predominantly based on ECSC (86.4%), followed by GLI (8.9%) and NHANES (0.25%). Mean spirometric values included FEV1 (% predicted) 57.2%, FVC (% predicted) 72.7%, and FEV1/FVC 61.9%. Cough in the first second of FVC was observed in 17 (3%) (=0.677), variable or insufficient effort 13.4% (=0.563), mouth leak 1.8% (=0.305), mouthpiece obstruction 0.5% (=0.332), rapid expiration 1.8% (=0.354), increased concavity 83% (=0.683), and small airway obstruction 87% (=0.709) were reported by interpreters.KKKKKKKK

CONCLUSION: Spirometry reports frequently lack key information such as preliminary diagnoses, test indication, technician, and device details. ECSC is the most commonly used reference. Rates of inconclusive and erroneous tests-due to variable or insufficient effort, mouth leak, mouthpiece obstruction, and rapid expiration-are low.