Potential limitations of clinical criteria for the diagnosis of idiopathic pulmonary fibrosis/cryptogenic fibrosing alveolitis.

Background: The need to perform surgical lung biopsy (SLB) in all cases of suspected idiopathic pulmonary fibrosis/cryptogenic fibrosing alveolitis (IPF/CFA) is controversial. The American Thoracic Society (ATS) and the European Respiratory Society (ERS) recently endorsed explicit clinical criteria for the diagnosis of IPF/CFA in the absence of SLB. Prior studies evaluating clinical criteria for the diagnosis of IPF/CFA have been limited in that either they were performed by clinicians with expertise in the diagnosis of IPF/CFA or they did not utilize explicit diagnostic criteria. We investigated the accuracy of the ATS/ERS criteria when applied in a general pulmonary medicine setting.

Objectives: To determine the interobserver variability of clinical criteria for the diagnosis of IPF/CFA.

Methods: This was a retrospective, blinded evaluation by three board certified pulmonary physicians without extensive experience in the evaluation of IPF/CFA performed at a United States Army tertiary care academic medical center. Patients referred for surgical lung biopsy as part of a diagnostic evaluation of interstitial lung disease (ILD) were evaluated. The physicians reviewed high-resolution computed tomography scans of the chest (HRCT) and clinical data for each patient. The physicians were blinded to all other data and to the opinions of other study participants. Employing the histologic presence of usual interstitial pneumonia (UIP) coupled with appropriate clinical findings as the gold standard for a diagnosis of IPF/CFA we determined the accuracy and interobserver variability for a diagnosis of IPF/CFA based on HRCT alone and based on the ATS/ERS clinical criteria.

Results: The sensitivity and positive predictive value for a HRCT diagnosis of IPF/CFA were 71% each while specificity and negative predictive value were 67% each. For the ATS/ERS criteria sensitivity, specificity, positive predictive value and negative predictive value were 71, 75, 77 and 69%, respectively. The interobserver variability, expressed as a kappa coefficient, for HRCT and the ATS/ERS criteria were 0.59 and 0.53, respectively.

Conclusions: Both HRCT and the ATS/ERS clinical criteria may lead to misdiagnosis of patients with ILD. Further studies are needed to fully characterize the accuracy of these tests when applied in a routine pulmonary medicine practice setting.