The planning of cancer screening programmes.

Positive screening tests require investigation, usually by specialists. Specialist services are known to be limited. The planning of screening programmes must first include a model of existing diagnostic and follow-up services of symptomatic patients so that the added impact of the extra referrals required for screening can be estimated. This is fundamental to the planning of screening programmes; inevitable diagnostic delay, impeded access to services for symptomatic patients, and resulting harm or increased mortality from disease can thus be avoided.