Clinical significance of histological UIP pattern in interstitial pneumonia with autoimmune features (IPAF)

Abstract

Background: The concept of IPAF was recently proposed as idiopathic interstitial pneumonia (IIP) with features suggestive of connective tissue disease. Usual interstitial pneumonia (UIP) pattern is well known prognostic factor in IIP, however clinical significance of UIP pattern in IPAF is uncertain. Objective: The aim of this study was to reveal prevalence and clinical significance of histological UIP pattern (h-UIP) in IPAF. Method: We retrospectively analyzed all 217 IIPs who underwent surgical lung biopsy (SLB) from January 2010 to December 2015. The diagnosis of IPAF was made according to the 2015 research statement, and morphologic domain criteria was only based on histological findings by SLB. To evaluate the relationship of h-UIP with annual deterioration and mortality rate, we use logistic regression models and cox proportional hazard models adjusted to GAP stage. Annual deterioration was defined as any of the following: >10% relative decline in FVC, lung transplantation, or death in one year from SLB. Result: 79 patients (36%) fulfilled IPAF criteria. In patients with IPAF, 26 patients (33%) had h-UIP. There was no significant difference in age, FVC and DL CO with or without h-UIP, but male was predominant with h-UIP (62% vs 34%, P=0.029). Logistic regression analysis showed that h-UIP was associated with annual deterioration [adjusted odds ratio 0.171, 95%Confidence interval (CI) (0.045–0.649), P=0.009]. Moreover, cox proportional hazard analysis revealed that h-UIP was a risk factor for mortality rate [adjusted hazard ratio 0.180, 95%CI (0.035 – 0.930), P=0.041]. Conclusion: h-UIP has impact on annual deterioration and mortality in IPAF.