Background/Purpose: Once specific etiologic factors have been ruled out, the majority of patients with chronic interstitial pneumonia (IP) can be classified as idiopathic pulmonary fibrosis (IPF) or as connective tissue autoimmune disease (CTD) associated. Being usual interstitial pneumonia (UIP) the reference radiographic pattern of IPF, a non-UIP pattern is one of the most robust indicators of an alternative diagnosis. In this regard, Fischer’s criteria of IP with autoimmune features (IPAF) include either a non-UIP radiographic pattern or the coexistence with alterations at other compartments. However, some patients presenting with UIP could have an autoimmune IP (AIP) and remain unclassified (UAIP). As it has been recently suggested, the involvement of the superior anterior lobe, an exuberant honeycombing and a straight edge between affected and unaffected regions could suggest an AIP diagnosis in patients with UIP. We set a retrospective study to describe the appearance of these atypical UIP signs in our clinic of AIP patients.

Methods: Two radiologists performed independent evaluations of CT scan images from our patients with AIP and an UIP pattern. Concordance was evaluated with kappa index. Epidemiological data, clinical diagnosis and process-associated variables were collected from clinical charts. Comparisons were assessed with non-parametric tests.

Results: Agreement between observer 1 (expert) and observer 2 (trainee) was fair as regards to the identification of the upper anterior lobe sign (p 0.001) and the straight edge (p < 0.001), while there was little concordance in the exuberant honeycombing scoring (p 0.7). We subsequently carried out the analysis using observer 1 scoring. There were 9 out of 33 p (27%) showing exuberant honeycombing, 5 p with involvement of the upper anterior lobe (15%) and 2 p with the straight edge sign (6%), irrespectively from the clinical diagnosis. The appearance of at least one of the signs was 62% in the CTD group, 43% in IPAF, and 30% in UAIP. In the UAIP cohort, 2 p had the anterior superior lobe sign. One of them did not fulfil the serological IPAF domain. The second one did not show involvement of other compartments, and had an ACPA titre of 264 IU. The third patient had an exuberant honeycombing, but no additional compartment involvement, along with a > 1/320 ANA titre. The last 2 patients would therefore change classification to IPAF if these signs were taken into account in the classification criteria. On the other hand, 2 patients had high rheumatoid factor but none had the atypical signs and would consequently remain unclassified. There was no association between atypical signs and inflammatory markers, such as glass-grounded opacities or acute phase reactants. Neither was there a relationship between these signs and disease duration time from or the extension of fibrosis. Interestingly, patients with emphysema were more likely to have any of the atypical UIP signs (p 0.047). We did not find associations between these signs and markers of epithelial injury. However, there was an inverse relationship with C’4 (p 0.041).

Conclusion: The new radiographic signs may help characterize a subgroup of patients with AIP, although more studies are necessary.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/atypical-pulmonary-radiographic-findings-may-help-identify-patients-with-usual-interstitial-pneumonia-and-autoimmune-features/