Demographic and Clinical Factors Associated With Diagnostic Confidence in Interstitial Lung Disease: Findings From the Pulmonary Fibrosis Foundation Patient Registry.

Background: Accurate diagnosis of interstitial lung disease (ILD) can be challenging. Accordingly, clinicians may attribute a diagnostic certainty based on guideline criteria and clinical judgment. However, further research is needed to refine this approach and improve diagnostic clarity. Research Question: What are the real-world factors associated with diagnostic confidence in fibrotic ILD? Study Design and Methods: Data were included from all patients enrolled in the Pulmonary Fibrosis Foundation Patient Registry from March 2016 to August 2018. Baseline demographic and clinical characteristics were collected at enrollment, or at the test date closest to the date of consent for longitudinal measures. Descriptive analyses were performed separately for all participants, and for subgroup participants with idiopathic pulmonary fibrosis (IPF) and participants with non-IPF ILD, stratified by the level of investigator diagnostic confidence (high vs medium/low) assigned at registry enrollment. Adjusted ORs and 95% CIs were calculated using multivariable logistic regression, with the aforementioned characteristics as predictors. Results: Data up to April 2022 from 1,992 participants were included. In adjusted logistic regression analyses among all participants, antifibrotic use (OR, 1.51; 95% CI, 1.09-2.07), longer time since diagnosis (OR, 0.94; 95% CI, 0.89-0.98) at the research unit of 365 days, and diabetes (OR, 2.56; 95% CI, 1.01-6.44) were significantly associated with higher diagnostic confidence, and non-IPF idiopathic interstitial pneumonia (vs IPF; OR, 0.36; 95% CI, 0.24-0.55), insurance - other (OR, 0.65; 95% CI, 0.43-0.97), and Hispanic ethnicity (OR, 0.54; 95% CI, 0.31-0.94) were significantly associated with lower diagnostic confidence. Factors associated with diagnostic confidence in the IPF and/or non-IPF ILD groups included age, male sex, region, immunomodulatory medication use, multidisciplinary team discussion, surgical lung biopsy, and definite high-resolution CT pattern. Interpretation: These findings suggest that certain demographic and clinical factors may influence physicians' confidence in diagnosis of IPF and non-IPF ILD. Tailored physician education may help to reduce biases and improve consistency in diagnosis.