Fibrotic idiopathic interstitial pneumonias: HRCT findings that predict mortality

The study aims were to identify CT features that predict outcome of fibrotic idiopathic interstitial pneumonia (IIP) when information from lung biopsy data is unavailable.

HRCTs of 146 consecutive patients presenting with fibrotic IIP were studied. Visual estimates were made of the extent of abnormal lung and proportional contribution of fine and coarse reticulation, microcystic (cysts ≤4 mm) and macrocystic honeycombing. A score for severity of traction bronchiectasis was also assigned. Using death as our primary outcome measure, variables were analysed using the Cox proportional hazards model.

CT features predictive of a worse outcome were coarse reticulation, microcystic and macrocystic honeycombing, as well as overall extent of lung abnormality (p < 0.001). Importantly, increased severity of traction bronchiectasis, corrected for extent of parenchymal abnormality, was predictive of poor prognosis regardless of the background pattern of abnormal lung (HR = 1.04, CI = 1.03-1.06, p < 0.001). On bivariate Cox analysis microcystic honeycombing was a more powerful determinant of a poor prognosis than macrocystic honeycombing.

In fibrotic IIPs we have shown that increasingly severe traction bronchiectasis is indicative of higher mortality irrespective of the HRCT pattern and extent of disease. Extent of microcystic honeycombing is a more powerful determinant of outcome than macrocystic honeycombing.