• cervical screening;
  • liquid-based cytology;
  • positive predictive value;
  • atypical predictive value;
  • total predictive value;
  • SurePath;
  • ThinPrep;
  • performance indicators;
  • dyskaryosis;
  • cervical intraepithelial neoplasia

P. K. Wright, J. Marshall and M. Desai

Comparison of SurePath®and ThinPrep®liquid-based cervical cytology using positive predictive value, atypical predictive value and total predictive value as performance indicators

Objective:  Two liquid-based cytology (LBC) systems are in widespread use in the UK: ThinPrep® and SurePath®. A number of studies have now compared LBC with conventional cytology in cervical screening. However, to date, we are aware of no studies that have compared ThinPrep® with SurePath® LBC. As the selection and use of specific diagnostic systems in a laboratory has significant clinical and economic implications, there is a clear need to compare directly existing LBC technology. The objective of this study was to compare ThinPrep® with SurePath® LBC in a single cytology laboratory using performance indicators.

Methods:  Data were collected for all cervical cytology samples processed at Manchester Cytology Centre over a 1-year period. ThinPrep® LBC was compared with SurePath® LBC using positive predictive value (PPV), atypical predictive value (APV) and total predictive value (TPV), reflecting outcome of cervical intraepithelial neoplasia (CIN) grade 2 or worse for high-grade dyskaryosis (PPV), low-grade dyskaryosis or borderline (atypical) cytology (APV) and all (total) abnormal cytology (TPV).

Results:  2287 (out of 56 467) (ThinPrep®) and 586 (out of 22 824) (SurePath®) samples showed borderline or worse cytology after exclusion criteria. PPV, APV and TPV were within acceptable ranges for both ThinPrep® and SurePath®.

Conclusions:  ThinPrep® and SurePath® were equivalent based on three performance indicators. We suggest that APV and TPV should be used as an adjunct to PPV and other methods of quality assurance for cervical screening.