Quantitative CT analysis of honeycombing area predicts mortality in idiopathic pulmonary fibrosis with definite usual interstitial pneumonia pattern: A retrospective cohort study

Abstract

Background: Honeycombing on high-resolution computed tomography (HRCT) images is a key finding in idiopathic pulmonary fibrosis (IPF). In IPF, honeycombing area determined by quantitative CT analysis is correlated with pulmonary function test findings. We hypothesized that quantitative CT-derived honeycombing area (HA) might predict mortality in patients with IPF.

Materials and methods: Chest HRCT images of 52 IPF patients with definite usual interstitial pneumonia (UIP) pattern were retrospectively evaluated. Mortality data up to July 31, 2016, were recorded. Using a computer-aided system, HA and percentage of HA (%HA) were measured quantitatively. Predictors of 3-year mortality were evaluated using logistic regression models.

Results: The median %HA, %predicted forced vital capacity (FVC) and composite physiologic index (CPI) were 3.8%, 83.6%, and 33.6, respectively. According to GAP (gender, age, and physiology) stage, 20, 14, and 5 patients were classified under stages I-II-III, respectively. Percentage of HA was significantly correlated with %FVC, CPI, and GAP stage (all, p < 0.001). In univariate analysis, %HA, %FVC, and CPI were statistically significant predictors of mortality. In multivariate analysis using the stepwise regression method, only %HA (odds ratio [OR], 1.27; p = 0.011) was a significant independent predictors of mortality. Patients with %HA ≥ 4.8% had significantly lower survival rates than those with lesser %HA (median survival time, 1.3 vs 5.0 years; log-rank test; p < 0.001).

Conclusion: Quantitative CT-derived HA might be an important and independent predictor of mortality in IPF patients with definite UIP pattern.

Fig 1. Honeycombing area detected by quantitative CT analysis.

A 76-year-old man with idiopathic pulmonary fibrosis. (A) Original CT image was acquired at the level of the lower lungs using the lung window setting. (B) Honeycombing area was detected by quantitative CT analysis at the same level.

Fig 2. Kaplan–Meier plot of survival probability.

The median survival times (interquartile ranges) were 1.3 (0.8–2.8) and 5.0 (2.1–5.9) years among patients with greater (≥ 4.8%; blue line) and smaller (< 4.8%; red line) %HA (log-rank test; p < 0.001), relative to the cutoff. %HA = computed-tomography-derived %honeycombing area.