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Extent of Fibrosis Predicts Mortality in Idiopathic Pulmonary Fibrosis

February 28, 2008
Written by: , Filed in: Chest Radiology
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The objective of a recent study was to evaluate quantitative CT indexes, CT visual scoring, and pulmonary function tests (PFTs) in predicting mortality of patients with IPF.

The study has concluded that in patients with idiopathic pulmonary fibrosis (IPF), the visual extent of fibrosis seen on CT is a strong independent predictor of mortality, and quantitative CT indexes can demonstrate progression of disease.

Participants
167 patients with IPF were included in this retrospective study. The diagnosis was based on history, PFTs, CT findings, and sometimes biopsy. All patients were required to have progression of IPF based upon PFTs, oxygen saturation measurements, or imaging findings. Patients excluded had end-stage IPF, severe heart disease, environmental or drug exposures felt to likely cause interstitial lung disease, connective tissue disease, and severe emphysema.

Methodology
All patients were randomized to receive either daily placebo or interferon beta-1a. Ninety-five of the patients had data sets for both baseline and follow-up. Follow-up ranged from 0.9 to 2.7 years. CTs were performed using thin sections (1 mm thick) at 2-cm intervals. The extent of ground glass opacity, reticular abnormality, honeycombing, and emphysema was recorded.

The mean extent of lung fibrosis was the average of the mean extent of reticular abnormality and honeycombing as scored by two radiologists in each of six lung zones.

Quantitative CT indexes of skewness, kurtosis, and mean lung attenuation were recorded. These indexes are computer-derived values that describe the shape of thin-section CT frequency histograms.

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Results of the Study
Thirty-five 35 patients (21.0%) died during the follow-up period. The administration of placebo or interferon beta-1a did not predict survival, PFT results, quantitative CT indexes, or visual CT scores. Univariate logistic regression analysis indicated the CT visual extent of fibrosis at baseline was the most significant predictor of death (P =0.003). The CT indexes of kurtosis (P =0.17) and skewness (P =0.035) at baseline also predicted death.

The total lung capacity as determined by PFTs at baseline (P =0.038) also predicted mortality. A higher fibrosis score and lower skewness, kurtosis, forced vital capacity, and total lung capacity at baseline predicted a greater likelihood of mortality.

The extent of ground glass opacity and emphysema on CT did not significantly predict mortality. Multivariate logistic regression analysis indicated that the CT visual extent of fibrosis was the best independent predictor of death (P =0.017).

In the 95 patients who had data sets for both baseline and follow-up, the CT visual extent of fibrosis demonstrated a slight increase and the CT indexes of mean lung attentuation, skewness, and kurtosis all demonstrated change indicating progression of disease.

Conclusions
The CT visual extent of fibrosis is a strong independent predictor of mortality in patients with IPF. Quantitative CT indexes during baseline and follow-up can also demonstrate disease progression.

Reviewer’s Comments
The authors acknowledge that one of the limitations of this study was the relatively short follow-up period.

Author: Vineet R. Jain, MD

Reference
Best AC, Meng J, et al. Idiopathic Pulmonary Fibrosis: Physiologic Tests, Quantitative CT Indexes, and CT Visual Scores as Predictors of Mortality.
Radiology; 2008;
246 (March): 935-940:

Review for Practicing Radiologists The University of California, San Francisco School of Medicine, Department of Radiology and Biomedical Imaging Review for Practicing Radiologists an intensive clinical radiologic review and self-assessment covering the following radiology subspecialties: Vascular-Interventional, Breast, Neuro, Gastrointestinal and Pulmonary Imaging. The program is designed for radiologists in clinical practice. Click here to read more or order: Review for Practicing Radiologists --

 

Body Imaging: Abdominal, Thoracic and Vascular University of California, San Francisco, Department of Radiology Course Director: Judy Yee, MD This program is designed for the radiologist in clinical practice, and is intended to provide an overview and update on clinically relevant topics in diagnostic imaging and interventional techniques. Click here to read more or order: Body Imaging
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