The predicted effect of changes in cervical screening practice in the UK: results from a modelling study

Abstract

In 2003, the National Health Service Cervical Screening Programme (NHSCSP) announced that its screening interval would be reduced to 3 years in women aged 25-49 and fixed at 5 years in those aged 50-64, and that women under 25 years will no longer be invited for screening. In order to assess these and possible further changes to cervical screening practice in the UK, we constructed a mathematical model of cervical HPV infection, cervical intraepithelial neoplasia and invasive cervical cancer, and of UK age-specific screening coverage rates, screening intervals and treatment efficacy. The predicted cumulative lifetime incidence of invasive cervical cancer in the UK is 1.70% in the absence of screening and 0.77% with pre-2003 screening practice. A reduction in lifetime incidence to 0.63% is predicted following the implementation of the 2003 NHSCSP recommendations, which represents a 63% reduction compared to incidence rates in the UK population if it were unscreened. The model suggests that, after the implementation of the 2003 recommendations, increasing the sensitivity of the screening test regime from its current average value of 56 to 90% would further reduce the cumulative lifetime incidence of invasive cervical cancer to 0.46%. Alternatively, extending screening to women aged 65-79 years would further reduce the lifetime incidence to 0.56%. Screening women aged 20-25 years would have minimal impact, with the cumulative lifetime incidence decreasing from 0.63 to 0.61%. In conclusion, the study supports the 2003 recommendations for changes to cervical screening intervals.

Figures

Figure 1

Markov model incorporating states for cervical HPV infection, CIN and treatment of screen-detected disease.

Figure 2

Prevalence of cervical HPV infection (PCR detectable HPV DNA) found in population surveys in the Netherlands and the USA, compared to the model prediction. aMelkert et al (1993); bSchiffman and Kjaer (2003).

Figure 3

Observed and predicted incidence of invasive cervical cancer in the UK. aCancer Registrations in England, 1998–2000. Office of National Statistics.

Figure 4

Predicted effect of 2003 NHS Cervical Screening Programme recommendations. aCancer Registrations in England, 1998–2000. Office of National Statistics.

Figure 5

Effect of varying the sensitivity of cervical screening, after implementing the 2003 screening interval changes.

Figure 6

Effect of extending screening to women aged 20–24 or 65–79 years, after implementing the 2003 screening interval changes.