• Margaret L Salisbury, Cheryl Markin, Tisra Fadely, Adam R Guttentag, Stephen M Humphries, David A Lynch, Jonathan A Kropski, and Timothy S Blackwell.
• Vanderbilt University Medical Center, Nashville, Tennessee, United States; mls8b8@gmail.com.
• Am. J. Respir. Crit. Care Med. 2024 Aug 13.

RationaleRelatives of patients with familial pulmonary fibrosis (FPF) are at increased risk to develop FPF. Interstitial lung abnormalities (ILAs) are a radiologic biomarker of subclinical disease, but the implications of very mild abnormalities remain unclear.ObjectivesTo quantify the progression risk among FPF relatives with abnormalities below the threshold for ILAs as described by the Fleischner Society and to describe the characteristics of participants with new or progressive ILAs during observation.MethodsAsymptomatic FPF relatives undergo serial screening high-resolution chest CT (HRCT). For this analysis, Early ILAs (no minimum threshold of lung involvement) were sub-classified as Mild (all interstitial abnormalities involve <5% of a lung zone) or Moderate (any abnormality involves >5%). Identification of new or progressive ILAs on HRCT, or development of Pulmonologist-diagnosed clinical FPF were defined as progression. Covariate-adjusted logistic regression identified progression-associated characteristics.Measurements And Main ResultsFrom 2008-2023, 273 participants in follow-up procedures were 53.2 9.4 years old at enrollment, 95 (35%) were male, and 73/268 (27%) were ever-smokers. During a mean follow-up of 6.2 3.0 years, progression occurred among 31/211 (15%) of those with absence of ILAs at enrollment, 32/49 (65%) of Mild ILAs, and 10/13 (77%) of Moderate ILAs. Mild ILAs had 9.15 (95% CI 4.40-19.00, p<0.0001) times and Moderate ILAs had 17.14 (95% CI 4.42-66.49, p<0.0001) times the odds of progression as subjects without ILAs.ConclusionsIn persons at-risk for FPF, minor interstitial abnormalities, including reticulation that is unilateral or involves <5% of a lung zone, frequently represent subclinical disease.

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