[371] Impact of HPV Vaccination on HPV Genotypes in Women with Atypical Cells of Undetermined Significance (ASC-US) in a Low-Risk Screening Population.

Roberto G Gamez, Stefan E Pambuccian, Bharat Thyagarajan, Shelly M Cook, Samy Amirouche, Evin H Gulbahce. University of Minnesota, Minneapolis

Background: HPV vaccination with the quadrivalent vaccine Gardasil® was approved by the FDA in June 2006 for use in females aged 9 to 26 and may also be useful in women aged 27-45. To date 44.3% of all U.S. females aged 13-17 have recieved at least one dose (MMWR 2010;59:1018-23). The aim of this study was to determine the potential impact of HPV vaccination on the HPV genotypes detected in women with ASC-US.
Design: All liquid-based (Surepath®) Pap tests diagnosed as ASC-US from 12/3/2002 to 6/30/2009 who had concomitant HPV genotyping were identified. Pap tests were diagnosed according to the 2001 Bethesda System; HPV tests were performed by a "home-brew" PCR-based method using the MY9/11 L1 consensus primers. The 13 HPV types included in the hc2 cocktail (16,18,31,33,35,39,45,51,52,56,58,59,68) were considered as high-rik HPV (HR-HPV). During the study period there were no major changes our screening population, laboratory personnel or molecular methods used. The study interval was divided into two periods: "pre-vaccination" (12/3/2002-6/30/2006) and "post-vaccination" (7/1/2006-6/30/2009). The frequecies of HPV 6, 11, 16 and 18 were compared between the two periods using χ².
Results: During the study period our laboratory processed 391,845 Pap tests.

	Total Pap tests	% ASC-US	ASC-US Age (mean± SD)	ASC/SIL ratio
Pre-vaccination period	215,784	5.31%	35.14 ± 12.89	2.48
Post-vaccination period	176,061	4.96%	35.62 ± 13.16	1.88
Total	391,845	5.15%	P val .018	2.18

16594 cases of ASC-US from women aged 11 to 89 (mean, 35.37 ± 13.02 SD) with concomitant valid HPV genotyping results were identified.

	Number ASC-US	any HPV type	hr-HPV+	HPV6	HPV11	HPV16	HPV18
Pre-Vaccine	8636	3767 (35.3%)	1773(16.65)	202 (6.3%)	24 (0.7%)	634 (19.7%)	155 (4.8%)
Post-Vaccine	7958	3284 (42.0%)	1666 (20.9%)	171 (5.5%)	28(0.9%)	522(17.7%)	169 (5.4%)
p value		<.001	<.001	.182	.578	.039	.305

There was an increase in the total HPV+ and HR-HPV+ rate in the post-vaccination period, most likely due to the more restrictive criteria for the diagnosis of ASC-US in this period, reflected in the lower ASC-US and ASC/SIL ratios. Despite this increase in the frequency of overall HPV+ and HR-HPV+ cases, there was a significant reduction in HPV16+ ASC-US cases.
Conclusions: Our study shows that, despite the relatively low vaccination rate, the incomplete vaccination status and the targeting of only younger women, HPV vaccination has resulted in a decrease of HPV16 as a cause of ASC-US in our population.
Category: Cytopathology

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 58, Monday Morning