P‐20 DIAGNOSTIC ACCURACY OF CONVENTIONAL SMEARS AND THINPREP SAMPLES IN CERVICAL SCREENING

Abstract

Objective: Liquid Based Cytology has been recommended in England and Wales as the primary means of processing samples in cervical screening programme. We conducted this study to compare the positive predictive value (PPV) of conventional smears (CS) and ThinPrep samples (TP) reported as high‐grade squamous dyskaryosis and glandular neoplasia from September ’01 to August ’05. The performance of both techniques was compared with histological results.Methods: The database of the cytology department was searched and figures were obtained from September 2001 to August 2004 for high‐grade dyskaryosis and from September 2001 to August 2005 for glandular neoplasia. Only primary care samples were taken into consideration for determining positive predictive value (PPV).Results: The total number of samples for CS and TP were 373 990 (86.8%) and 48 216 (11.2%) respectively. Inadequate rate for CS and TP was 10.68% and 1.64% respectively. PPV of moderate and severe dyskaryosis including invasive carcinoma in CS was 71.7% and 90.4%; while for TP, it was 65.8% and 89.4% respectively. PPV of glandular neoplasia for CGIN/Adenocarcinoma was 66.7% and 64.3% in CS and TP respectively. PPV of glandular neoplasia for CIN2 and more in CS and TP was 82.7% and 85.7% respectively. The PPV for a diagnosis of CIN2 or worse in CS and TP was 79.3% and 73.3% respectively.Discussion: The PPV for a diagnosis of CIN2 or worse in both systems are within acceptable range for the U.K. (65–87%). The difference in PPV for varied categories in both systems is statistically insignificant. The inadequate rate is significantly reduced with TP.