reciprocal of difference number needed to screen to prevent A statistic that represents the number of units that needs to be tested to prevent one additional adverse outcome, assuming that positive testing will lead to preventive intervention. The Number Needed to Screen to Prevent is calculated as the Number Needed to Treat divided by the prevalence. Comment for application: The Number Needed to Screen (NNS) value is often rounded up to the next highest whole integer. The Number Needed to Screen to Detect is distinct from the Number Needed to Screen to Prevent as the formulas to calculate are different, even though both may be abbreviated as NNS. The formula may be adjusted for test performance characteristics (e.g. dividing by the sensitivity) or assumptions regarding acceptance or adherence of interventions. Number needed to screen was then calculated by dividing the number needed to treat for treating risk factors by the prevalence of disease that was unrecognised or untreated. https://www.bmj.com/content/317/7154/307.long Number needed to screen was then calculated by dividing the number needed to treat for treating risk factors by the prevalence of disease that was unrecognised or untreated. https://www.bmj.com/content/317/7154/307.long Brian S. Alper, Harold Lehmann, Joanne Dehnbostel, Kenneth Wilkins, Janice Tufte NNS Expert Working Group Agreement: 2022-08-03 vote 5-0 by Jesus Lopez-Alcalde, Janice Tufte, Eric Harvey, Philippe Rocca-Serra, Harold Lehmann ready for release