Poor interpretation of pulmonary function tests in patients with concomitant decreases in FEV1 and FVC

Background and objective:   A new interpretative strategy for pulmonary function tests (PFT) has been proposed by the American Thoracic Society/European Respiratory Society (ATS/ERS) Task Force. To assess the accuracy of this strategy, clinical diagnosis was compared with the PFT interpretation in patients showing concomitant decreases in FEV₁ and FVC.
Methods:   A retrospective study was conducted of 681 patients with normal FEV₁/FVC and low FVC who underwent lung volume measurements and spirometry on the same date between July and November 2005 at Asan Medical Center, Seoul, Korea. Patients were clinically diagnosed by the consensus decision of two respiratory physicians, and the kappa coefficient was calculated to compare the clinical diagnosis with the PFT interpretation using the ATS/ERS strategy.
Results:   The PFT interpretation showed an obstructive pattern in 205 patients and a restrictive pattern in 476. Of the 205 patients with an obstructive pattern on PFT, 44 were clinically diagnosed with obstructive, 97 with restrictive and 17 with mixed disease, whereas 47 patients had no disease. Of the 476 patients with a restrictive pattern on PFT, 11 were clinically diagnosed with obstructive, 369 with restrictive and 60 with mixed disease, whereas 36 patients had no disease. The kappa coefficient was 0.35 (95% confidence interval: 0.26–0.44; P  < 0.0001).
Conclusions:   The weak agreement between the clinical diagnosis and the PFT interpretation in patients showing concomitant decreases in FEV₁ and FVC suggests that other clinical findings should be assessed in addition to PFT.