"reciprocal of the absolute risk reduction is the NNS: 1/0.00312=320.5"
"The number needed to screen (NNS) is the number of patients that need to undergo screening to prevent one death by the disease being screened for 1,2."
"Results from the National Lung Screening Trial (NLST) indicate an number needed to screen for low-dose CT for lung cancer screening of 320. That means that 320 subjects need to be screened to save one person from dying of lung cancer 3. The number was calculated using data from subjects who were screened at least once. There were 425 lung cancer deaths out of 26,232 subjects in the group screened with chest x-ray (considered the unscreened group) and 346 lung cancer deaths out of 26,455 subjects in the low-dose CT group. NNS calculations for the NLST were:"
"reciprocal of the absolute risk reduction is the NNS: 1/0.00312=320.5"
"risk of death from lung cancer in the chest X-ray group is 425/26,232=0.01620"
"risk of death from lung cancer in the chest X-ray group is 425/26,232=0.01620"
"risk of death from lung cancer in the low-dose CT group is 346/26,455=0.01308"
"absolute risk reduction is 0.01620-0.01308=0.00312"
"absolute risk reduction is 0.01620-0.01308=0.00312"
"absolute risk reduction is 0.01620-0.01308=0.00312"
"reciprocal of the absolute risk reduction is the NNS: 1/0.00312=320.5"
Expected headings
"Calculation"
"Example"
"Limitations and assumptions"