Reliability study of pulmonary function tests in patients with chronic obstructive pulmonary disease

COPD is frequently underdiagnosed due to low rates of spirometry utilization and inaccuracies in test quality. This multicenter, prospective, observational study aimed to evaluate the quality of spirometry tests from six tertiary-care-centers, by two pulmonologists. Inter-rater reliability was determined using Cohen's Kappa Test(K). The study included 120 females and 436 males(65.92±10.25 years). 443(79.10%) tests were interpreted as obstruction, 32(5.7%) restriction, 15(2.68%) mixed pattern, 31(5.53%) normal, 31(5.53%) inconclusive, 7(1.25%) small airway obstruction, and 1(0.18%) as upper airway obstruction(K=0.890). Postbronchodilator testing was conducted in 397(71%) tests. Volume-time graphs were included in 495(88.5%), flow-volume loops in 556(99.64%) and inspiratory limbs were present in 550(98.74%) reports. Reference values showed that ESCS, GLI, and NHANES were used in 343(86.4%), 36(8.93%), and 1(0.25%) tests, respectively. The mean values of maximal expiratory flow rates were: FEV1(%predicted) 57.17±23.09, FVC(%predicted) 72.7±24.97, FEV1/FVC(%) 61.91±14.31, FEF25-75(%predicted) 31.81±24.85, and FET(sec) 5.61±1.88. Cough in the first second of FVC was observed in 114(2.55%)(K=0.650), variable-insufficient effort 13.4%(K=0.563), mouth leak 1.8(K=0.305), mouthpiece obstruction 0.5%(K=0.332), rapid expiration 1.8%(K=0.354), increased concavity 83%(K=0.683), and small airway obstruction 87%(K=0.709) were reported by interpreters. The rates of inconclusive and erroneous tests due to variable effort, insufficient effort, mouth leak, mouthpiece obstruction, and rapid expiration are low. Obstructive pattern with increased concavity and small airway obstruction were predominant.