Diagnostic Likelihood Thresholds That Define a Working Diagnosis of Idiopathic Pulmonary Fibrosis.

Rationale: The level of diagnostic likelihood at which physicians prescribe antifibrotic therapy without requesting surgical lung biopsy (SLB) in patients suspected of idiopathic pulmonary fibrosis (IPF) is unknown.Objectives: To determine how often physicians advocate SLB in patient subgroups defined by IPF likelihood and risk associated with SLB, and to identify the level of diagnostic likelihood at which physicians prescribe antifibrotic therapy with requesting SLB.Methods: An international cohort of respiratory physicians evaluated 60 cases of interstitial lung disease, giving: 1) differential diagnoses with diagnostic likelihood; 2) a decision on the need for SLB; and 3) initial management. Diagnoses were stratified according to diagnostic likelihood bands described by Ryerson and colleagues.Measurements and Main Results: A total of 404 physicians evaluated the 60 cases (24,240 physician-patient evaluations). IPF was part of the differential diagnosis in 9,958/24,240 (41.1%) of all physician-patient evaluations. SLB was requested in 8.1%, 29.6%, and 48.4% of definite, provisional high-confidence and provisional low-confidence diagnoses of IPF, respectively. In 63.0% of provisional high-confidence IPF diagnoses, antifibrotic therapy was prescribed without requesting SLB. No significant mortality difference was observed between cases given a definite diagnosis of IPF (90-100% diagnostic likelihood) and cases given a provisional high-confidence IPF diagnosis (hazard ratio, 0.97; P = 0.65; 95% confidence interval, 0.90-1.04).Conclusions: Most respiratory physicians prescribe antifibrotic therapy without requesting an SLB if a provisional high-confidence diagnosis or "working diagnosis" of IPF can be made (likelihood ≥ 70%). SLB is recommended in only a minority of patients with suspected, but not definite, IPF.

Diagnostic accuracy of a clinical diagnosis of idiopathic pulmonary fibrosis: an international case-cohort study.

We conducted an international study of idiopathic pulmonary fibrosis (IPF) diagnosis among a large group of physicians and compared their diagnostic performance to a panel of IPF experts.A total of 1141 respiratory physicians and 34 IPF experts participated. Participants evaluated 60 cases of interstitial lung disease (ILD) without interdisciplinary consultation. Diagnostic agreement was measured using the weighted kappa coefficient (κw). Prognostic discrimination between IPF and other ILDs was used to validate diagnostic accuracy for first-choice diagnoses of IPF and were compared using the C-index.A total of 404 physicians completed the study. Agreement for IPF diagnosis was higher among expert physicians (κw=0.65, IQR 0.53-0.72, p<0.0001) than academic physicians (κw=0.56, IQR 0.45-0.65, p<0.0001) or physicians with access to multidisciplinary team (MDT) meetings (κw=0.54, IQR 0.45-0.64, p<0.0001). The prognostic accuracy of academic physicians with >20 years of experience (C-index=0.72, IQR 0.0-0.73, p=0.229) and non-university hospital physicians with more than 20 years of experience, attending weekly MDT meetings (C-index=0.72, IQR 0.70-0.72, p=0.052), did not differ significantly (p=0.229 and p=0.052 respectively) from the expert panel (C-index=0.74 IQR 0.72-0.75).Experienced respiratory physicians at university-based institutions diagnose IPF with similar prognostic accuracy to IPF experts. Regular MDT meeting attendance improves the prognostic accuracy of experienced non-university practitioners to levels achieved by IPF experts.