CT Features of the Usual Interstitial Pneumonia Pattern: Differentiating Connective Tissue Disease-Associated Interstitial Lung Disease From Idiopathic Pulmonary Fibrosis

AJR Am J Roentgenol. 2018 Feb;210(2):307-313. doi: 10.2214/AJR.17.18384. Epub 2017 Nov 15.


Objective: A substantial proportion of cases of usual interstitial pneumonia (UIP) are due to connective tissue disease (CTD)-associated interstitial lung disease (ILD). The purpose of this study was to determine whether specific CT findings can help differentiate a UIP pattern of CTD-ILD from a UIP pattern of idiopathic pulmonary fibrosis (IPF) and whether these signs are associated with survival.

Materials and methods: Adults visiting an ILD clinic from 2006 to 2015 enrolled in a research registry with a multidisciplinary diagnosis of CTD-ILD or IPF and a UIP pattern at high-resolution CT were included in the study. In these subjects with CT findings of UIP due to either IPF or CTD-ILD, three CT findings anecdotally associated with CTD-ILD were assessed for diagnostic accuracy: the "straight-edge" sign, the "exuberant honeycombing" sign, and the "anterior upper lobe" sign. Survival assessments were performed with univariate and multivariable techniques.

Results: The subjects included 63 patients who had CTD-ILD and 133 patients who had IPF with a UIP pattern at CT. All three CT signs were significantly more common in subjects with CTD-ILD than those with IPF (prevalence, 22.2-25.4% for CTD-ILD, 6.0-12.8% for IPF; p = 0.028 to < 0.001). The highest specificity (94.0%) and sensitivity (25.4%) were seen for the straight-edge sign. No CT sign was associated with survival in multivariable analysis.

Conclusion: Although UIP is usually associated with IPF, the index of suspicion for CTD-ILD should be raised in the care of patients with any of the three CT signs. A thorough workup for CTD-ILD should be pursued, including referral to the rheumatology department.

Keywords: connective tissue disease; idiopathic pulmonary fibrosis; survival; usual interstitial pneumonia.

MeSH terms

  • Adult
  • Aged
  • Connective Tissue Diseases / diagnostic imaging*
  • Diagnosis, Differential
  • Female
  • Humans
  • Idiopathic Pulmonary Fibrosis / diagnostic imaging*
  • Lung Diseases, Interstitial / diagnostic imaging*
  • Male
  • Middle Aged
  • Registries
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed / methods*