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

Comparison of SurePath (R) and ThinPrep (R) 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 (R) and SurePath (R). 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 (R) with SurePath (R) 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 (R) with SurePath (R) 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 (R) LBC was compared with SurePath (R) 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 (R)) and 586 (out of 22 824) (SurePath (R)) samples showed borderline or worse cytology after exclusion criteria. PPV, APV and TPV were within acceptable ranges for both ThinPrep (R) and SurePath (R). Conclusions: ThinPrep (R) and SurePath (R) 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.