HPV testing of biobanked liquid-based cytology - a validation study.

Abstract

The aim of the study was to investigate whether biobanked liquid-based cytology (LBC) vaginal samples could be reanalyzed for the biomarkers HPV DNA and mRNA without loss of sensitivity. One hundred LBC samples with ASCUS or CIN1 were tested for HPV DNA and mRNA before and after biobanking. DNA analysis targeted the viral genes E6 and E7, 12 high-risk and 2 low-risk HPV types together with the human control gene HBB, using real-time PCR. The Aptima HPV assay was used for mRNA analysis of 14 high-risk HPV types. With Aptima there was 84% agreement between results before and after biobanking. The sensitivity and specificity were 0.79 (95% CI, 0.68-0.88) and 0.94 (95% CI, 0.80-0.99), respectively. With the DNA-based method, the agreement between results was 87%, the sensitivity 0.85 (95% CI, 0.75-0.92) and the specificity 0.95 (95% CI, 0.77-1.00). Both methods presented a significant difference between positive results before and after biobanking; McNemar test: p = 0.004, p = 0.003, Cohen's kappa: 0.67 (95% CI, 0.53-0.81), 0.68 (95% CI, 0.52-0.84). Cycle threshold values for the DNA method were higher for all genotypes after biobanking, except for HPV-59. Some loss of sensitivity was seen after biobanking but the concordance between HPV detection before and after biobanking was good for both evaluated methods. Biobanking of LBC vaginal samples offers a good platform for HPV testing and could be extended to further molecular analyses. However, in order to ensure a valid test result a larger portion needs to be analyzed from the biobanked sample.