Significant variation in performance does not reflect the effectiveness of the cervical cancer screening programme in...

To characterise the variation in performance indicators of the Finnish cervical screening programme by screening laboratory and to assess whether the performance affects cervical cancer incidence.

Cervical cancer screening data from 1999 to 2003 from six well-established laboratories were used to analyse rates for follow-up recommendations, referrals and histologically confirmed dysplastic lesions. Laboratory-specific cervical cancer incidences for 1954-2003 were assessed using the cancer registry files.

Differences in follow-up recommendations were up to 3.1-fold and 2.2-fold in referrals; differences in the rates for CIN1, CIN2 and CIN3+ were up to 4.5-, 4.7-, and 1.5-fold, respectively. Pre-screening incidence rates for cervical cancer varied 1.5-fold by laboratory, with no major differences in the incidence trends since the onset of screening.

The performance of a cervical screening programme differs by screening laboratory but does not materially affect the overall programme effectiveness. This leads to variation in cost-effectiveness and probably in avoidable adverse effects. In cervical cancer screening studies, the outcome should be selected as closely as possible to the true measure of programme effectiveness, prevented invasive cervical cancers and subsequent deaths.