Prevalence Threshold and Public Health

In this chapter, we discuss the use of the prevalence threshold in the Public Health domain, in particular, as it pertains to the administration of screening programs. We describe the concept of the number needed to screen (NNS) as well as the number needed to harm (NNH) and introduce the NNS optimization theorem as a means to improve the yield of public health screening programs. We likewise show how this in turn optimizes \(\Gamma \) , also known as “Likelihood of Being Helped or Harmed”, defined as the ratio of the NNH to NNS.