Performance of ACR Lung-RADS in a clinical CT lung screening program

J Am Coll Radiol. 2015 Mar;12(3):273-6. doi: 10.1016/j.jacr.2014.08.004. Epub 2014 Aug 28.


Purpose: The aim of this study was to assess the effect of applying ACR Lung-RADS in a clinical CT lung screening program on the frequency of positive and false-negative findings.

Methods: Consecutive, clinical CT lung screening examinations performed from January 2012 through May 2014 were retroactively reclassified using the new ACR Lung-RADS structured reporting system. All examinations had initially been interpreted by radiologists credentialed in structured CT lung screening reporting following the National Comprehensive Cancer Network's Clinical Practice Guidelines in Oncology: Lung Cancer Screening (version 1.2012), which incorporated positive thresholds modeled after those in the National Lung Screening Trial. The positive rate, number of false-negative findings, and positive predictive value were recalculated using the ACR Lung-RADS-specific positive solid/part-solid nodule diameter threshold of 6 mm and nonsolid (ground-glass) threshold of 2 cm. False negatives were defined as cases reclassified as benign under ACR Lung-RADS that were diagnosed with malignancies within 12 months of the baseline examination.

Results: A total of 2,180 high-risk patients underwent baseline CT lung screening during the study interval; no clinical follow-up was available in 577 patients (26%). ACR Lung-RADS reduced the overall positive rate from 27.6% to 10.6%. No false negatives were present in the 152 patients with >12-month follow-up reclassified as benign. Applying ACR Lung-RADS increased the positive predictive value for diagnosed malignancy in 1,603 patients with follow-up from 6.9% to 17.3%.

Conclusions: The application of ACR Lung-RADS increased the positive predictive value in our CT lung screening cohort by a factor of 2.5, to 17.3%, without increasing the number of examinations with false-negative results.

Keywords: CT lung screening; Lung-RADS.

MeSH terms

  • Diagnostic Errors / prevention & control*
  • Diagnostic Errors / statistics & numerical data
  • Early Detection of Cancer / standards*
  • Early Detection of Cancer / statistics & numerical data*
  • Female
  • Humans
  • Lung Neoplasms / diagnostic imaging*
  • Male
  • Middle Aged
  • Quality Assurance, Health Care / methods
  • Quality Assurance, Health Care / statistics & numerical data
  • Radiology Information Systems / standards
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed / standards*
  • Tomography, X-Ray Computed / statistics & numerical data*
  • United States