Lung-RADS and nodule reporting

A screening programme that biopsied every shadow would harm more people than it helped, so every programme runs a structured reporting system that maps nodule features to an action. Lung-RADS, the American Lung Imaging Reporting and Data System, categorises the most suspicious nodule on the scan and assigns a follow-up interval or a referral; the NELSON protocol instead measures nodule volume automatically and, for indeterminate nodules, the volume doubling time between scans, referring only those that grow fast enough. The choice matters as much as the eligibility rule: 24.2 percent of low-dose CT screens in the National Lung Screening Trial were called positive, and 96.4 percent of those were false, while NELSON referred only 2.1 percent of participants for a suspicious nodule, and 9.2 percent had one extra scan for an initially indeterminate result. The US Preventive Services Task Force noted in 2021 that most of the trials it reviewed predated current nodule protocols, and that modern protocols should lower the false-positive and invasive-procedure rates below what the trials measured. England's programme runs a national protocol with linked quality assurance standards for exactly this reason, so that a nodule gets the same answer wherever it is scanned.