Infection with the human papillomavirus (HPV) is a cause of cervical cancer, but only a small percentage of all infections will ultimately lead to cervical cancer if left untreated. In Sweden, women between the ages of 23 and 59 years are invited to undergo screening for cervical cancer every third (ages 23–49) to fifth year (ages 50–59). Since 2009, liquid-based cytology (LBC) has been the method of choice. Presently, the Swedish Biobanking and Molecular Resource Infrastructure (BBMRI) is establishing a population-based biobank of 100,000 cervical cytology samples each year. It is a collaboration between nine Swedish universities to study LBC vaginal samples for HPV DNA and mRNA without losing sensitivity when reusing collected, stored samples.
Larsson et al. (2016) used 100 cervical samples with diagnoses of atypical squamous cells of undetermined significance (ASCUS), now referred to as cervical intraepithelial neoplasia, level 1 (CIN1).1 All of the samples were from women 35 years or older and had been forwarded for HPV testing. The team stored the repository plates in a –20°C freezer for two to six months and thawed them before performing secondary DNA or mRNA analysis. They used real-time polymerase chain reaction (PCR) to perform DNA analysis and an Aptima HPV assay for mRNA analysis.
Prior to biobanking, 67 of the samples were high-risk HPV positive with the Aptima HPV assay and 78 were high-risk HPV positive with the DNA real-time PCR. However, after biobanking, 55 of the samples were high-risk HPV positive with the Aptima HPV assay and 67 were high-risk HPV positive with the DNA real-time PCR. Overall, more samples were positive for HPV using DNA detection compared to mRNA detection both before and after biobanking.
The authors suggest that they had good concordance between HPV detection before and after biobanking, using both methods, indicating that the process doesn’t entirely hinder repeat positive results. However, they acknowledge there was some sensitivity loss as a result of biobanking, as they lost 14 RNA results and 12 DNA results. Furthermore, the DNA-based real-time PCR method had higher sensitivity for HPV, which they believe indicates that RNA may be more vulnerable to biobanking than DNA.
1. Larsson, G.L, et al. (2016) “HPV testing of biobanked liquid-based cytology – A validation study.” doi: 10.5301/jbm.5000191.