Cytological screening for cervical cancer prevention.

Historically, the incidence and mortality of cervical cancer has declined in countries that have instituted and sustained mass-organised cytology-based screening programmes. These programmes, however, required frequent repeats of the screening tests. They also require a functioning healthcare infrastructure, with laboratories for smear processing and interpretation, mechanisms for quality control, referral for colposcopy, treatment of precursors, and follow-up to detect failures of treatment. Although this approach has been successful in preventing cervical cancer where implemented correctly, it has proved inordinately complex and expensive for developing countries. Consequently, no successful screening programmes have been established in poor countries, and cervical cancer remains the most common cancer among women in developing countries, despite the existence of cytology and the knowledge of cervical cancer prevention. New technologies, specifically the development of liquid-based cytology, have improved the performance of cytology as a screening test, but do not obviate the infrastructural challenges posed to health systems by cytology-based screening programmes. In this chapter, the history of cytological screening and the challenges posed by secondary prevention strategies are reviewed.