PURPOSE: While lung cancer screening (LCS) with low dose chest CT (LDCT) is recommended for high-risk populations, little is known about how clinical screening compares with research trials. We compared Lung-RADS scores between a nationally screened population from the American College of Radiology's (ACR) LCS Registry (LCSR) and the National Lung Screening Trial (NLST). METHODS: This retrospective study included baseline LDCT exams from the LCSR and NLST. Patient characteristics (age, gender, smoking status, pack-years, and body mass index (BMI)) were obtained. NLST LDCT results were recoded to Lung-RADS version 1.1. A multivariable multinomial logistic model was used to examine variations in Lung-RADS scores by screening group (LCSR versus NLST) and patient characteristics. RESULTS: 686,011 and 26,432 participants from the LCSR and NLST, respectively, were included. Compared to the NLST, the LCSR population was older (mean age (SD): 64.0 (5.4) versus 61.4 (5.0) years), p<
0.002), included more females (47.9% versus 40.9%, p<
0.002), and more likely to be currently smoking (61.5% versus 48.1%, p<
0.002). After adjusting for age, gender, smoking history, and BMI, the LCSR population was more likely to have higher Lung-RADS scores than the NLST (adjusted odds ratio (aOR) and 95%CI >
1 for Lung-RADS scores 2, 3, 4A, 4B, 4X relative to Lung-RADS 1). CONCLUSIONS: Lung-RADS scores in clinical LCS are higher than in the NLST, even after adjusting for known confounders such as age and smoking. This would imply higher rates of follow-up testing after LCS and potentially higher cancer rates in the clinically screened population than the NLST.