Nonspecific interstitial pneumonia: Correlation between thin-section CT findings and pathologic subgroups in 55 patients

PURPOSE: To characterize thin-section computed tomographic (CT) findings of pathologic subgroups of nonspecific interstitial pneumonia (NIP) in a sizeable number of patients. MATERIALS AND METHODS: The study included 55 cases of pathologically proven NIP. The 55 cases were categorized histologically into four grades: grade 1, interstitial inflammation without fibrosis (n = 6); grade 2, interstitial inflammation predominating over fibrosis (n = 16); grade 3, fibrosis predominating over inflammation (n = 5); and grade 4, fibrosis only (n = 28). Two independent observers evaluated the presence, extent, and distribution of various CT findings. Thin-section CT findings and histologic grades were compared by using the Spearman rank correlation coefficient. Observer agreement was assessed. RESULTS: Areas with ground-glass attenuation and architectural distortion were present in all 55 patients. Traction bronchiectasis and intralobular reticular opacities were seen in 52 and 48 patients, respectively. The extent of traction bronchiectasis (r = 0.68; P < .001) and intralobular reticular opacities (r = 0.35; P < .05) correlated with the histologic grade. Honeycombing was seen in 12 (43%) of 28 patients with grade 4 NIP and in three (11%) of the remaining 27 patients (X² test, P < .001). There was good agreement between the observers for the presence (κ = 0.7-1.0) and extent (Spearman rank correlation; r = 0.87-0.98; P < .001) of various abnormalities. CONCLUSION: The extent of traction bronchiectasis and intralobular reticulation at thin-section CT correlates with increased fibrosis in NIP. Honeycombing is seen almost exclusively in patients with fibrotic NIP.