Evaluation of proficiency testing as a method of assessing competence to screen cervical smears.

Regular proficiency testing of pathologists and cytotechnologists who undertake the analysis of cervical smears has been carried out in cytology laboratories in the North Thames (West) region since 1989. The protocol followed is one that has been adopted nationally. Since the scheme started, laboratory personnel from 17 cytology laboratories in the Region have participated and seven rounds of testing have been completed. Nine hundred and seventy-one tests were carried out and a pass rate of 96.4% was recorded. Two hundred and forty-seven cytologists took the test on at least one occasion and 63 cytologists took part in all seven rounds. Our results indicate that proficiency testing is capable of detecting cytologists who consistently perform below an acceptable standard and require retraining. They also show that even the most competent screeners can miss an abnormal smear. Seven cytologists who had proved their competence to screen on six occasions, missed an abnormal smear on the seventh, despite the fact that they were screening under test conditions when their vigilance should have been at its peak. Our findings indicate that false-negative reporting will inevitable occur during manual screening, and emphasize the need for further research into the causes and prevention of screening error.