Comparison between Siriraj liquid-based and conventional cytology for detection of abnormal cervicovaginal smears: A split-sample study

Abstract

This study aimed to evaluate the correlation and agreement between Siriraj liquid-based cervical cytology (Siriraj -LBC) and conventional cytology. A total of 479 women who attended the Department of Obstetric and Gynaecology Siriraj Hospital for cervical cancer screening were enrolled. For each woman collection of cervical cells was performed using VCE technique. After smearing cells on a glass slide for conventional cytology, both broken ends of wooden spatula and cotton swabs were then placed into a plastic vial containing a specific preservative solution for Siriraj-LBC. All specimens were prepared and interpreted by experienced cytotechnologists at the Gynecologic Cytology Unit. Interpretations of the results from one technique were made without knowledge of those from the other technique. The results from both techniques were compared for agreement and correlation. Colposcopy or histology was used as the gold standard. The overall detection rate of abnormal cervicovaginal cells was higher by Siriraj-LBC than by conventional cytology (11.1% vs. 1.67%, P <0.001). These two techniques had high diagnostic agreement of 89.77%, and minimal to fair correlation with a Kappa of 0.128 (P< 0.001) and a Spearman rho correlation coefficient of 0.394 (P <0.001). There were 49 cases whose Siriraj-LBC revealed higher cytologic grading than did the conventional cytology; there were no cases of the opposite result. The gold standard was available in 45 cases with abnormal cytology by Siriraj-LBC, revealing a positive predictive value (PPV) of 71.1% for Siriraj-LBC and 97.8% for conventional cytology, and a negative predictive value (NPV) of 42.2% for the conventional cytology. In conclusion, The results from Siriraj-LBC and conventional cytology have high diagnostic agreement and minimal to fair correlation. The Siriraj-LBC increases detection rate of abnormal cervicovaginal cells with probable decrease in false negatives but increase in false positives from the baseline values by conventional cytology. Therefore the screening performance of Siriraj-LBC is not inferior to the conventional cytology and this approach may be used as an alternative screening method for cervical cancer.