Prevalence of genital HPV infection in a population-based pilot study in women living in Canada.

Transcription

1 Prevalence of genital HPV infection in a population-based pilot study in women living in Canada.

2 Forest P., Goggin P., Lavoie F., Sauvageau C., Gilca V., Dubé E., Deceuninck G., Coutlée F. Centre Hospitalier de l Université de Montréal, Institut national de santé publique du Québec, Centre Hospitalier de l Université Laval Research. Center. Financial disclosure: reagents for the Linear Array were provided by Roche Diagnostics Canada. The study was supported by le Ministère de la Santé et des Services Sociaux du Québec.

3 Background An HPV vaccination program for girls aged 9-17 years has been implemented since 2008 in the Province of Quebec, Canada. The impact of vaccination will be assessed prospectively in our population of women. Genotype-specific rates of HPV infection in unvaccinated female populations allow us to fully evaluate the impact of HPV vaccination on the distribution of HPV genotypes. Unfortunately, population-based estimations of HPV type-specific prevalence are not available for our province.

4 *flocked swabs (Copan Italia, Brescia Italy) Objectives The main goal of the pilot study (poster 833) was to develop and validate a method to measure the prevalence and distribution of the various HPV genotypes in a population-based sample. Specific goals of this substudy: To assess the quality of mailed self-obtained cervico-vaginal dry swabs* for PCR To estimate the detection rates of HPV genotypes in women selected randomly.

5 Methods Women aged living in two regions of Québec participating in a web survey (see poster 833) were asked to take part in a prevalence study. A sampling kit was mailed to 237 women accepting to participate and included instructions for self-sampling at home and a dry flosked swab. 166 (70%) women sent back a self-collected cervico-vaginal dry swab by regular mail. Exfoliated cells were resuspended in 500 µl of Preservcyt. Samples were then processed for DNA with the Qiagen Amplilute Media Extraction kit and quantitated by spectrophotometry. HPV detection was done with the Linear Array (L.A.) HPV Genotyping Test from Roche Diagnostics, capable of detecting 36 HPV anogenital types.

6 Testing with HPV Linear Array Gravitt, P. E. et al J. Clin. Microbiol. 36(10):

7 Results: Quality of 166 samples for PCR 166 dry swab samples were processed and tested Quantity of extracted DNA (total volume=120µl): average: 62.5 ng per µl (95% CI ) median: 45.5 ng per µl range: ng per µl. Two aliquots of samples were tested by L.A. 1: volume equivalent to 400 ng of DNA ( ng) 2: fixed volume of 15 µl for all samples. β-globin testing results: 165 (99.4%) + with ng of DNA 164 (98.8%) + testing 15 µl of extracted DNA.

8 Results: HPV prevalence analyzing ng of DNA per test Exclusion of 9 women: previous vaccination against HPV (n=8) a negative reaction for β-globin (n=1). Results on the 157 samples tested: HPV + 68 (43.3%, 95% CI ) High Risk HPV+ 47 (29.9%, 95% CI ) Low Risk HPV+ 39 (24.8%, 95% CI ). Tables and Figures: Table 1: HPV Screening results for the 157 samples. Table 2: Effect on HPV type detection of testing different volumes of the samples. Figure 1: Distribution of single and multiple type infections.

9 TABLE 1: HPV Screening Results for our 157 Survey Participants. * High Risk Types: 16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68 and 82. HPV TYPE No.(%) Positive Samples As Single As Multiple 6 4 (2.5) (0) NA NA 16* 13 (8.3) * 6 (3.8) * 0 (0) NA NA 31* 10 (6.4) * 1 (0.6) (64) 0 (0) NA NA 35* 2 (1.3) * 4 (2.5) (0.6) (7.6) (55) 3 (1.9) * 2 (1.3) * 4 (2.5) * 1 (0.6) * 6 (3.8) (2.5) * 8 (5.1) * 6 (3.8) * 5 (3.2) (3.2) (3.8) * 5 (3.2) (1.9) * 2 (1.3) (0) NA NA 70 2 (1.3) (0) NA NA 72 1 (0.6) (3.2) (1.3) (IS39)* 3 (1.9) (2.5) (3.2) (5.7) 2 7

10 Figure 1: Distribution of single and multiple type infections Number of Samples HPV Negative 56.7% HPV Positive 43.3% Single 21.7% Multiple 21.7% Double 8.3% Triple 6.4% Quadruple 3.8% Five or more Types 3.2%

11 Table 2: Effect on HPV type detection of testing different volumes of the samples. ID# Gain of an HPV type with LA at 15ul Loss of an HPV type with LA at 15ul β-globin (Loss/Gain) Loss

12 Discussion and limitations Most samples were appropriate for HPV typing despite the use of dry swabs via regular mail. Self-sampling yielded an abundance of biological material. A 4-fold dilution was done prior to processing the samples to avoid overloading the Qiagen columns. Nearly half of participants were infected by HPV. An important proportion of genital HPV infections are caused by more than one type. Single-type infections by high-risk types were more frequent than those caused by low-risk types.

13 Conclusions Dry swabs are appropriate for HPV analysis and typing, and can facilitate the performance of population-based studies. Most samples contained human cells. Yet the optimal volume to test needs to be determined. The prevalence of HPV and High Risk HPV infections was high in our population. HPV-16 was the most frequent genotype.