Protein biomarkers of interstitial lung abnormalities in relatives of patients with pulmonary fibrosis

Rationale First-degree relatives of patients with pulmonary fibrosis (referred to here as relatives) are at high risk for interstitial lung abnormalities (ILA), highlighting the need for biomarkers for risk prediction. We aimed to identify blood proteins associated with and predictive of ILA among relatives of patients with pulmonary fibrosis. Methods Relatives enrolled in two independent cohorts had protein levels measured using an aptamer-based proteomic platform. ILA were assessed with computed tomography scans as per Fleischner Society recommendations. Protein associations with ILA were assessed using regression. Significant proteins were used with clinical variables to detect ILA. Results Of 237 relatives from two independent cohorts, 26% had ILA. Seven proteins were associated with ILA in the discovery cohort after false discovery rate adjustment, and all remained significant after adjusting for age, gender and smoking status. Six of the seven proteins were significantly associated in the validation cohort, including growth differentiation factor 15, surfactant protein D and surfactant protein B. In a multivariable model, six proteins combined with basic demographics in the discovery cohort had an area under the curve of 0.92 (0.88 in the validation cohort). Least absolute shrinkage and selection operator modelling identified three proteins and age as predictors, with an area under the curve of 0.89 in the validation cohort. When applied to the combined cohorts, this simple model would reduce the need for computed tomography imaging in one of every three relatives screened. Conclusion Peripheral blood proteins are associated with ILA in relatives of patients with pulmonary fibrosis and can be used to detect them. Our findings demonstrate the potential use of blood biomarkers in this high-risk group and suggest molecular targets for future investigation.