ABC3 Part II: a review of the new criteria for evaluating cervical cytology in England
The new Achievable Standards, Benchmarks for Reporting, and Criteria for Evaluating Cervical Cytopathology, 3rd edn (ABC3) includes radical changes in the criteria for evaluating cervical cytology. First, they include a new mission statement ‘the objective of cervical screening is to reduce cervical cancer incidence and mortality by screening with a high sensitivity for the detection of CIN2 or worse, whilst maintaining a high specificity’.
Second, the original four performance measurement criteria where laboratories were examined further if they were below the 10th or above the 90th percentile has been changed to three and laboratories are only mandatorily examined if they fall below the 5th or above the 95th percentile. The old criteria related to the percentage of samples that were inadequate, the percentage of all adequate samples reported as moderate dyskaryosis or worse (equivalent to high-grade squamous intraepithelial lesion or cancer), the percentage of adequate samples reported as mild dyskaryosis or borderline (equivalent to low-grade squamous intraepithelial lesion or atypical squamous/glandular cells) and the positive predictive value. The new criteria are percentage of inadequate samples, positive predictive value and a new measure termed referral value. These changes mean that far fewer laboratories will require mandatory examination.
Third, a raft of optional performance measures have been introduced to help laboratories examine their annual statistical return to the Department of Health in comparison with other laboratories. These measures have been designed to produce a more uniform national programme, and to help laboratories decide whether they are maximizing the benefit of screening while minimizing the harm, which is the goal of all screening programmes. This review examines in detail the new criteria and explains in more detail some of the thinking behind them.