Table 4. Number of patients who need to be screened in order to prevent one disease-specific death.

	NNS*	Time period
Fecal occult blood test	808	8.5 years
Colonoscopy	862	13 years
Mammography (women aged 50 to 69 years)	Approx 2000	10 years
Ultrasound of the abdominal aorta (men aged 65 to 80 years)	350	7–15 years

^* numbers needed to screen (24, 25)