Criteria for the diagnosis of idiopathic pleuroparenchymal fibroelastosis: A proposal. 
Physicians have few opportunities to perform surgical lung biopsy (SLB) to diagnose idiopathic pleuroparenchymal fibroelastosis (IPPFE).  Therefore, diagnostic criteria for IPPFE that do not require SLB must be established.  Herein, we propose diagnostic criteria for IPPFE with and without SLB.  The diagnostic criteria for IPPFE with SLB are histological, based on computed tomography (CT) lesions compatible with PPFE, predominantly in the upper lobes.  The three diagnostic criteria for IPPFE without SLB are as follows: (1) radiologically possible IPPFE (a radiological criterion confirming CT lesions in both lung apexes, regardless of the lower lobe lesions); (2) radiologically probable IPPFE (also a radiological criterion, but mandatory to confirm chest radiograph findings of bilateral upward shift of the hilar structures and/or CT findings of volume loss of the upper lobes); (3) radiologically and physiologically probable IPPFE.  Our data from 41 patients with IPPFE and 97 with idiopathic pulmonary fibrosis (IPF) showed that the percentage of the predicted values of the ratio of residual volume to total lung capacity (RV/TLC %pred.)  ≥115% and body mass index (BMI) ≤20 kg/m2 plus RV/TLC %pred.  ≥80% performed well for discriminating IPPFE from IPF.  These parameters were thus added to criterion (3).  We have proposed diagnostic criteria for IPPFE in patients with and without SLB.  Both imaging criteria and physiological criteria using RV/TLC and BMI successfully discriminate IPPFE from chronic IIPs when SLB cannot be performed.