Predictive factors of idiopathic pulmonary fibrosis (IPF) in patients with a possible or inconsistent with usual interstitial pneumonia (UIP) pattern on high resolution computed tomography (HRCT)

Abstract

Introduction: In patients with chronic fibrosing idiopathic interstitial pneumonias (IIPs) and a possible or inconsistent with UIP pattern on HRCT, surgical lung biopsy (SLB) is required to make a definitive diagnosis between IPF and nonspecific interstitial pneumonia (NSIP) after multidisciplinary discussion (MDD). The aim of the study was to determine the predictive factors of IPF in this context. Methods: This monocentric retrospective study was based on a cohort of 289 IIPs patients. We included cases with a possible or inconsistent with UIP pattern on HRCT and a final diagnosis of IPF or NSIP after SLB and MDD. A multivariate logistic regression was used to analyse the predictive factors of IPF diagnosis. Patients with unclassifiable IIPs, mainly due to the absence of SLB, served as a validation cohort. Results: Among patients with a possible or inconsistent with UIP pattern (IPF:n=31, PINS:n=36), age>65 years was the best threshold indicative of IPF by a ROC curve. After adjustment for tobacco and sex, age>65 years (OR=3.35, p=0.046) and FVC decline>5% at 6 months (OR=3.46, p=0.047) were the strongest independent predictors of IPF. The combination of age>65 years + FVC decline>5% had a specificity of 94% and positive predictive value of 75%. In patients with unclassifiable IIPs (n=101), those with age>65 years + FVC decline>5% had a worse survival compared to others (median survival: 3.1 vs 8.8 years, p Conclusion: The combination of age and functional decline may help differentiate IPF and NSIP and assist clinicians in therapeutic decisions for patients who cannot undergo SLB.