Reticulation is a Risk Factor of Progressive Subpleural non-Fibrotic Interstitial Lung Abnormalities

Rationale: Interstitial lung abnormalities (ILAs) are being increasingly identified in clinical \r\npractice. In particular for subpleural non-fibrotic ILAs, the risk of progression over time and \r\nthe risk factors for progressive behavior are still largely unknown.\r\n\r\nObjectives: To determine the age band prevalence of ILAs and the risk of radiological \r\nprogression of subpleural non-fibrotic ILAs over time in a large health check-up population, \r\nand to identify how reticulation contributes to the risk of radiological progression.\r\n\r\nMethods: Based on ILAs definition by the Fleischner Society, low-dose chest CT images from \r\ncommunity-dwelling population undergone health check-up were evaluated for ILAs. \r\nMultivariable logistic regression was used to assess the risk of radiological progression.\r\nMeasurements and Main Results: Among 155,539 individuals, 3,300 (2.1%) were confirmed \r\nto have ILAs: the vast majority (81.7%) were defined as subpleural non-fibrotic ILAs. The \r\nprevalence of ILAs increased linearly with age (P for trend<0.0001). Of 454 individuals with \r\nsubpleural non-fibrotic ILAs, 198 (43.6%) had radiological progression over 4 years. The \r\npresence of reticulation on initial imaging was an independent predictor of radiological \r\nprogression (OR 1.9; 95%CI 1.2-3.0, P=0.0040). No difference in radiological progression was \r\nidentified between subpleural non-fibrotic ILAs with extensive reticulation and subpleural \r\nfibrotic ILAs (73.0% vs. 68.8%, P=0.7626).\r\n\r\nConclusions: The prevalence of ILAs increases linearly with age. Nearly half of subpleural \r\nnon-fibrotic ILAs progress radiologically over 4 years. The presence of reticulation is a risk \r\nfactor for radiological progression. Subpleural non-fibrotic ILAs with extensive reticulation \r\nare likely to be a feature of subpleural fibrotic ILAs.