Quantification of so-called honeycombing areas (patches of cystic spaces) in the lungs seen through high-resolution computed tomography (HRCT) may be a predictor of mortality in people with idiopathic pulmonary fibrosis (IPF), according to a retrospective analysis.
The study, “Quantitative CT analysis of honeycombing area predicts mortality in idiopathic pulmonary fibrosis with definite usual interstitial pneumonia pattern: A retrospective cohort study,” was published in the journal Plos One.
Lung function parameters such as forced vital capacity (FVC), forced expiratory volume (FEV), and diffusing capacity of the lungs for carbon monoxide (DLCO) are standard measures when assessing IPF. Still, results from these approaches often confound with coexisting emphysema (damage of the air sacs, causing shortness of breath); hence, more reliable markers or assessment strategies for IPF are needed.
Most patients with IPF show histopathologic patterns called usual interstitial pneumonia (UIP), which can be characterized by computed tomography scans. UIP patterns can be seen in HRCT images as groups of cystic spaces called honeycombing in the lungs.
Since increased honeycombing area relative to lung volume is predictive of IPF mortality, honeycombing quantification can help to improve the prognosis and management of IPF patients. However, current approaches to quantify relative honeycombing area are either limited by their varying results among experiments, or are based on methods that are hard to use.
Researchers have now developed a computer-aided system — relying on a public image processing program (ImageJ) — to quantify relative honeycomb areas using HRCT imaging. Using this approach, the team evaluated the link between honeycombing areas and mortality in IPF patients.
The study enrolled 52 IPF patients (mean age 75) with HRCT data from clinical visits, and available data for at least three years of follow-up (based on the median survival time for general IPF populations). Forty-five participants had available results from lung function tests.
Apart from measuring relative honeycombing areas using chest HRCT images, researchers also compared the participants’ lung function-associated parameters (FVC, FEV, and DLCO) when available.
Results showed that the relative honeycombing area of IPF participants (median 3.8%) correlated negatively with the lung function parameters FVC, FEV, and DLCO. Honeycombing area percentage also showed significant correlation with the composite physiologic index (CPI), which includes data from CT imaging, FVC, FEV, and DLCO, to establish a combined score of pulmonary fibrosis.
At the end of the three-year follow-up period, 29 of the 52 participants were alive. Primary analysis showed that mortality correlated with lower body mass index and %FVC. These results also indicated that mortality was associated with higher relative honeycombing area, and gender and age physiology (GAP) index, a predictor of prognosis and mortality in IPF.
However, further statistical analyses showed that honeycombing area was the only significant independent predictor of three-year mortality.
Researchers found that a value of 4.8 percent of honeycombing area served as a mortality cutoff — the median survival times were 1.3 and five years, respectively, among patients with honeycombing area greater and lesser than 4.8%.
“These findings show that [honeycombing area] might be a quantitative prognostic factor in IPF,” the researchers stated.
Although the study only included IPF patients with HRCT-defined UIP patterns, the team believes that the results might be comparable with the general IPF population.
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