Effect of glacial acetic acid treatment of cervical ThinPrep specimens on HPV DNA detection with the cobas 4800 HPV test

Abstract

Cytology laboratories in the UK routinely treat unsatisfactory cervical liquid-based cytology (LBC) specimens with glacial acetic acid (GAA) to reduce the unsatisfactory rate. However, there is limited published data on the effect of GAA reprocessing on the molecular detection of human papillomavirus (HPV). The aim of this study was to assess the impact of GAA treatment of cervical ThinPrep(®) samples on HPV detection with the cobas(®) 4800 HPV Test (Roche Molecular Systems, Pleasanton, CA, USA). Residual ThinPrep samples (n=121) were selected to provide a range of typical cytology results and enrich the study samples for HPV positivity. Specimens were equally split into two fractions: one part treated with 10% GAA and the other part left untreated. All samples were HPV tested using the cobas 4800 HPV Test, which simultaneously detects a total of 14 high-risk HPV (hrHPV) genotypes and individually identifies HPV16 and HPV18. The HPV positive/negative status of tested samples determined the level of agreement between treated and untreated fractions; one sample failed owing to detection of a clot by the instrument during pipetting, leaving 120 samples in the study. Statistical analysis was performed using an unweighted kappa. Analysis of overall HPV positivity showed 97.5% (117/120) agreement between the treated and untreated fractions with a kappa value of 0.95. There were 63/65 (96.9%) concordant HPV positive and 54/55 (98.2%) concordant HPV negative results. In addition to the three discordant results for overall HPV positivity, there were three HPV type-specific discrepancies giving a total of 114/120 concordant HPV results (95% agreement). Glacial acetic acid (GAA) treatment of cervical ThinPrep specimens does not have significant adverse affects on HPV detection with the cobas 4800 HPV Test.