Effectiveness and efficiency of opportunistic cervical cancer screening: comparison with organized screening.

BACKGROUND: Several countries have adopted nationally organized cervical screening programs, but many continue with opportunistic screening. Comparison of the effectiveness and efficiency of the 2 systems is important for informing policy.
OBJECTIVES: The objectives of this study were to assess the effectiveness and efficiency of an opportunistic cervical screening system, and to compare this with what could be achieved through an organized program. RESEARCH
DESIGN: We propose a model for estimating the effectiveness and efficiency of opportunistic screening systems and demonstrate it using data from a cross-sectional study of 1826 women in Hong Kong. We estimated the coverage and frequency of screening and used this to estimate effectiveness (number of cases of invasive cervical cancer potentially prevented) and efficiency (tests per case prevented) of the current system. Similar estimates were made for various organized programs with different screening intervals and coverage.
RESULTS: Ever screening coverage in this opportunistic system was 44%, resulting in 26% to 31% reduction in potential new cases (n = 144-183). Compared with this, a 3-yearly or 5-yearly screening policy aiming for 80% coverage would prevent an additional 46% (equivalent to 254 new cases out of a population of 2.3 million women per year) and 41% (222 per year), respectively. This could be achieved with more efficient use of resources, reducing the number of tests per case prevented from 2018 to 1545 and 1007, respectively.
CONCLUSIONS: At best, the effectiveness of this opportunistic system is equivalent to an organized program with 10-yearly screening and 50% coverage but at much greater cost. Poor coverage and over screening of a minority of women contributes to its inefficiency.