Key points

• Screening is a tool to identify people at increased risk of a condition so that preventative action can be taken.

• Established criteria are used to judge when a screening programme should be introduced. These take account of the importance of the condition, the test, the treatment and the effectiveness of the programme as a whole.

• The performance of a screening test can be evaluated using calculations of sensitivity, specificity, predictive values and likelihood ratios.

• Screening will always identify so-called false negatives and false positives.

• Screening programmes are evaluated in the short and long term and potential sources of bias are considered in determining their effectiveness.

• Screening can incur harm and raises ethical questions. Health professionals and the public need to be aware of both the costs and benefits to society and individuals from screening as a public health activity.

Introduction

Screening is one of the most important preventive public health activities. This chapter provides some examples of effective screening programmes, considers what criteria are needed to demonstrate the effectiveness of a programme, how screening tests can be used to guide action and how screening programmes can be evaluated.