Prevalence and genotype distribution of HPV and cervical pathological results in Sichuan Province, China: a three years surveys prior to mass HPV vaccination

doi:10.21203/rs.2.24630/v1

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Prevalence and genotype distribution of HPV and cervical pathological results in Sichuan Province, China: a three years surveys prior to mass HPV vaccination

https://doi.org/10.21203/rs.2.24630/v1

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published 10 Jul, 2020

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Background HPV persistent infection is a strong carcinogenic factor to induce cervical cancer. Investigation of HPV epidemiology and genotype distribution is meaningful for the development cervical cancer prevention and control strategies.

Methods By using PCR-based hybridization gene chip assay, HPV genotype was detected of 14185 women that came from HEC (Health Examination Center) or OGOC (Obstetrics and Gynecology Outpatient Clinics) between 2015 and 2017 in Sichuan area. The epidemiology and genotype distribution as well as the relationship to in histology and cytology abnormalities were analysed.

Results The positivity of HPV was 23.84%. The HPV-positive rate of OGOC group (37.62%) is significantly higher than that of HEC group (15.29%), p <0.05. The prevalence of HPV reached peak at 41-50 age (5.86%) in HEC group, but at 21-30 age (14.74%) in OGOC group. Of the HPV positive women, single genotype infection was the most common form in both HEC and OGOC group, accounted for 62.06% in total screening population, 74.36% in HEC group and 54.01% in OGOC group. Three most prevalent HPV types were HPV-52 (5.02%), 58 (3.61%), 16 (3.24%) in total screening population. Of the HPV positive women, the top three were HPV-52 (20.93%), CP8304 (15.32%), 58 (14.42%) in HEC group, while were HPV-52 (21.14%), 16 (16.34%), 58 (15.61%) in OGOC group. HPV 52/16/58 accounted for the 41.84% of cytology and 56.52% of histological abnormalities.

Conclusions Women in Sichuan area are facing with the great threat of HPV infection, especially the women of 21~30 or 41-50 years old. HPV 52, 58, 16 were the priority HPV type in OGOC group, while in in HEC group is HPV 52, CP8304, 58. HPV 52/16/58 accounted for the majority of cytology and histological abnormalities. These accurate data could provide a scientiﬁc basis for the prevention and control strategies of cervical cancer in Sichuan area.

Virology

Human papillomavirus

Genotype distribution

Sichuan area

HPV vaccination

Cervical cancer is the fourth most common cancer and the fourth leading cause of cancer death for women, with an estimated 570, 000 case and 311,000 deaths in 2018 worldwide. It is a serious threat to female health, especially in the developing countries[1]. China, as the most populous developing country, has 98,900 new cases of cervical cancer and 30,500 cervical cancer-related deaths in 2015[2].Therefore, China faces serious disease burden of cervical cancer.

Human papillomaviruses (HPVs) are non-enveloped, double-stranded circular DNA viruses. To date, > 170 types of HPV have been identified, of which, 40 infect the genital tract. Generally, they can be divided into low-risk categories (e.g. HPV 6, 11, 42, 43, 44, CP8304) which were mainly found in the genital warts, and high-risk categories (e.g. HPV 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66 and 68) ,the persistent infection of which has been recognized as a strong carcinogenic factor to induce cervical[3]^,[4]. Because of the huge different ability to induce cervical cancer, it is meaningful to investigate HPV DNA genotype to enhancing the effect of cervical cancer screening.

For the prevention of cervical cancer, HPV vaccines has showed a great potential. The prophylactic injection of HPV vaccine can declines in vaccine-type HPV prevalence and lead to substantial reductions in HPV-associated cancers[5]. However, the vaccines showed prominently type-restricted prophylactic efficacy. They merely induce immunity specific to certain HPV genotypes, and are unable to fend off other genotypes of the virus[4]. Studies also demonstrated that the distribution of HPV genotypes differs considerably both geographically and among populations. Therefore, to investigate the epidemiology and genotype distribution of HPV in a certain population is meaningful for the development of HPV vaccine strategy in this area[6].

Sichuan, a province in southwestern China, has the fourth largest population in the country, with a permanent population of 83.41 million in 2018(data from National Bureau of Statistics of China, http://www.stats.gov.cn/). Recently years, several studies aimed to investigate the epidemiology and genotype distribution of HPV in this area. However, the results varies in different studies[7–12].

In this study, in order to get a more accurate and reliable data, we audited large-scale retrospective data on cervical HPV testing and detection among women attending Health Examination Center (HEC) and obstetrics and gynecology outpatient clinics (OGOC) during 2015–2017, and also assessed type-specific prevalence of HPV and its connection to the findings in histology and cytology triage, to provide a scientific basis for the prevention and control strategies of cervical cancer in Sichuan area.

Study population and include criteria

A total of 14185 women who participated in HPV screening in Health Examination Center (HEC) and obstetrics and gynecology outpatient clinics (OGOC) of Sichuan People's Hospital were included from 2015 to 2017. The participants were enrolled according to the following selection criteria: (1) was mentally and physically competent; (2) sexually active women of any age; (3) are willing to undergo HPV testing. The age of the patients ranged from 14 to 78 years with an average of 39.93 ± 10.38 years.

Cervical sample collection

Samples exfoliated cervical cells were collected by using plastic cervical swabs. Each plastic swab was mixed well with 1 ml of specimen transport medium (Chaozhou Hybribio Biotechnology Limited Corporation, China) for HPV DNA testing, and store immediately at 4℃,and finally sent to our clinical laboratory with in one day for HPV analysis.

HPV DNA extraction and genotyping

HPV DNA extraction and genotyping DNA was performed by using Alkaline Lysis Method Kits and HPV GenoArray Test kit according to the manufacturer’s protocol (Chaozhou Hybribio Biotechnology Limited Corporation, China). Briefly, 1 ml of transport medium containing cervical cell were centrifuged at 14000 rpm for 5 min, then the HPV-DNA was extracted from the cells using Alkaline Lysis Method Kits. Then, PCR was performed with a reaction volume of 26 µl containing 2 µl HPV-DNA template, 23.25 µl of master mixture provided, and 0.75 µl of DNA Taq polymerase in a 7500 real time PCR system (Applied Biosystems). The amplification protocol was as follows: 9 min of denaturation at 95℃, followed by 40 cycles of denaturation at 95℃ for 20 sec, annealing at 55℃ for 30 sec, and extension at 72℃ for 30 sec, at last a final extension at 72℃ for 5 min. Genotyping was done by flow-through hybridization using HPV GenoArray Test kit. The chip could identify 15 HR-HPV (high-risk HPV) types (16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66 and 68) and 6 LR-HPV (low-risk HPV) types (6, 11, 42, 43, 44 and CP8304 in Chinese population). The final results were detected by colorimetric change on the chip under direct visualization.

Thin prep liquid-based cytology test

For cytology test, cervical slides were prepared using Liquid-PREP™ System (LGM International, USA). The slides were evaluated for cervical cytology by two academic cyto-pathologists of Sichuan Provincial People’s Hospital. Cytological classifications of disease grade were made in conformity to the Bethesda 2001 criteria, including negative of intraepithelial lesion or malignancy (NILM), atypical squamous cells of undetermined significance (ASCUS), atypical gland cell (AGC),low-grade squamous intraepithelial lesion (LSIL), high-grade squamous intra epithelial lesion (HSIL) and invasive cervical cancer (ICC).

Histology diagnosis

For cervical biopsies, Digital Electronic Colposcope (Olympus Company, Japan) was used by specially trained physicians to perform the cervical biopsy tissue collection. The histology results had been obtained by two academic Gynecology doctors of Sichuan Provincial People’s Hospital. A diagnosis was assigned to each case as having NO Lesion, cervical intraepithelial neoplasia grade 1 (CIN 1), CIN 2, CIN 3, cervical cancer (CA)

Statistical analysis

All statistical analyses were performed using SPSS 22.0 software (SPSS Inc., Chicago, IL, USA). Type-specific prevalence of HPV infection and their exact binomial 95% confidence intervals (CI) were calculated. Pearson’s χ² test was performed to evaluate the significance of differences between designated groups. All analyses were two-sided and interpreted as being significant at p < 0.05.

Prevalence of HPV infection in HEC and OGOC group

Overall, 14185 women were included in this study. Among them, 3382 were HPV positive, account for 23.84%. Among the 14185 women, 8751 came from HEC, and 5434 came from OGOC. The HPV-positive rate of OGOC group (37.62%) is significantly higher than that of HEC group (15.29%), p < 0.05.

Prevalence of HPV grouped by age in study population

All the participants were divided into seven groups range from ≤ 20 years, 21–30 years, 31–40 years, 41–50 years, 51–60 years, 61–70 years and ≥ 71 years. The prevalence of HPV exhibited reached a peak at 21–30 years and 41–50 years, with a positive proportion of 6.70% and 6.42%, respectively. Specific to different groups, the prevalence of HPV reached peak at 41–50 years group (5.86%) in HEC group, but at 21–30 years group (14.74%) in OGOC group (Table 2, Fig. 1).

Table 2

Prevalence of HPV single/multiple infection in HEC and OGOC group
Prevalence of HPV infection	Total HPV⁺		HEC HPV⁺		OGOC HPV⁺
Prevalence of HPV infection	n	%*	n	%*	n	%*
Single Infection	2099	62.06	995	74.36	1104	54.01
Mutlple Infection	1283	37.94	343	25.64	940	45.99
Double Infection	903	26.70	267	19.96	636	31.12
Triple Infection	266	7.87	64	4.78	202	9.88
Quadruple Infection	76	2.25	11	0.82	65	3.18
Quintet Infection	22	0.65	0	0.00	22	1.08
Sextuple Infection	10	0.30	1	0.07	9	0.44
Septuple Infection	6	0.18	0	0.00	6	0.29
Total Infection	3382	100.00	1338	100.00	2044	100.00
*: Percentage of each infection form in HPV positive women of Total/HEC/OGOC group.

Prevalence of HPV single and multiple HPV genotypes infection

Of the HPV positive women, single genotype infection was the most common form in both HEC and OGOC group, accounted for 62.06% in total, 74.36% in HEC and 54.01% in OGOC. Among the multiple infections, double genotype infection was the most, and the infection rate decreased significantly as the number of infected genotypes increased. In HEC group (Table 1). The most genotype of coinfection is sextuple infection in HEC group, is septuple infection in OGOC group. OGOC group showed a significantly higher prevalence rate of multiple genotype infection than HEC group (p < 0.05).

Table 1

Prevalence of HPV infection in different age groups
Age Group (Year)	Total case		HPV positive cases
	Total case		HEC		OGOC		Total
	n	%^#	n	%*	n	%*	n	%*
< 20	151	1.06	1	0.01	86	1.58	87	0.61
21–30	3013	21.24	149	1.70	801	14.74	950	6.70
31–40	4090	28.83	404	4.62	462	8.50	866	6.11
41–50	4753	33.51	513	5.86	397	7.31	910	6.42
51–60	1719	12.12	220	2.51	215	3.96	435	3.07
61–70	403	2.84	47	0.54	75	1.38	122	0.86
> 71	56	0.39	4	0.05	8	0.15	12	0.08
Total	14185	100.00	1338	15.29	2044	37.62	3382	23.84
#: Percentage of each age group
*: Percentage of HPV positive cases in each age group in HEC/OGOC /Total group.

Prevalence of HPV genotypes in HPV-positive population

Among 21 types of HPV our chip could identify, there were 15 high-risk types (HPV16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68) and 6 low-risk types (6, 11, 42,43, 44, CP8304). In our study, the three most prevalent HPV types were HPV-52 (5.02%), 58 (3.61%), 16 (3.24%) in total screening population, and followed by CP8304 (13.10%) and 53(12.12%). As shown in Table 3, among the HPV positive population, the genotypes of infected HPV vary between different groups. In HEC group, the top three were HPV-52 (20.93%), CP8304 (15.32%), 58 (14.42%), followed by 53(13.75%) and 16(9.42%). While in OGOC group, the top three were HPV-52 (21.14%), 16 (16.34%), 58 (15.61%), followed by CP8304 (11.63%) and 53(11.06%). HPV 16, 18,6, 11 subtype detections were significantly higher among OGOC group than HEC group. Interestingly, HPV 53 and CP8304 subtype detections were significantly higher among HEC group than OGOC group.

Table 3

Prevalence of HPV genotypes in HPV-positive population
	Total HPV+				HEC HPV+				OGOC HPV+				p^#
	S% (n = 2478)	M% (n = 904)	T% (n = 3382)	CI (95%) (n = 3382)	S% (n = 1052)	M% (n = 267)	T% (n = 1319)	CI(95%) (n = 1319)	S% (n = 1426)	M% (n = 637)	T% (n = 2063)	CI (95%) (n = 2063)	p^#
High Risk
16	8.10	5.50	13.60	12.45–14.76	5.98	3.44	9.42	7.85–10.98	9.49	6.85	16.34	14.74–17.94	< 0.001*
18	2.28	2.69	4.97	4.24–5.70	2.24	1.79	4.04	2.98–5.09	2.30	3.28	5.58	4.58–6.57	0.044*
31	1.77	1.77	3.55	2.92–4.17	1.79	1.27	3.06	2.14–3.99	1.76	2.10	3.86	3.03–4.70	0.218
33	2.75	2.28	5.03	4.29–5.76	3.21	1.42	4.63	3.51–5.76	2.45	2.84	5.28	4.31–6.25	0.398
35	0.50	0.59	1.09	0.74–1.44	0.75	0.45	1.20	0.61–1.78	0.34	0.68	1.03	0.59–1.46	0.645
39	4.82	4.46	9.28	8.31–10.26	5.53	3.44	8.97	7.44–10.50	4.35	5.14	9.49	8.22–10.76	0.609
45	0.33	0.68	1.01	0.67–1.34	0.45	0.52	0.97	0.45–1.50	0.24	0.78	1.03	0.59–1.46	0.874
51	3.78	4.70	8.52	7.57–9.46	4.71	3.36	8.07	6.61–9.53	3.18	5.58	8.81	7.58–10.03	0.454
52	12.89	8.16	21.05	19.68–22.43	14.13	6.80	20.93	18.75–23.11	12.08	9.05	21.14	19.37–22.90	0.884
53	6.80	5.32	12.12	11.02–13.22	9.49	4.26	13.75	11.91–15.60	5.04	6.02	11.06	9.70-12.42	0.019*
56	1.21	1.86	3.08	2.49–3.66	1.12	1.27	2.39	1.57–3.21	1.27	2.25	3.52	2.72–4.32	0.063
58	9.05	6.09	15.14	13.93–16.35	9.42	5.01	14.42	12.54–16.31	8.81	6.80	15.61	14.03–17.18	0.348
59	1.12	1.27	2.40	1.88–2.91	0.90	0.97	1.87	1.14–2.59	1.27	1.47	2.74	2.03–3.45	0.105
66	1.98	2.25	4.23	3.55–4.91	2.54	1.42	3.96	2.92–5.01	1.61	2.79	4.40	3.51–5.29	0.532
68	2.40	2.72	5.12	4.37–5.86	2.77	2.32	5.08	3.91–6.26	2.15	2.98	5.14	4.18–6.09	0.944
Low Risk
6	2.96	3.64	6.62	5.79–7.46	0.82	0.90	1.72	1.02–2.42	4.35	5.48	9.83	8.54–11.12	< 0.001*
11	2.40	2.87	5.26	4.51–6.02	1.05	0.67	1.72	1.02–2.42	3.28	4.26	7.58	6.44–8.73	< 0.001*
42	0.06	0.30	0.35	0.15–0.56	0.07	0.00	0.07	-0.07 ~ 0.22	0.05	0.49	0.54	0.22–0.86	0.055
43	0.18	0.30	0.47	0.24–0.70	0.15	0.07	0.22	-0.03-0.48	0.20	0.44	0.64	0.29–0.98	0.088
44	1.01	0.98	1.98	1.51–2.45	1.42	1.05	2.47	1.64–3.30	0.73	0.93	1.66	1.11–2.22	0.101
CP8304	6.89	6.21	13.10	11.96–14.24	10.09	5.23	15.32	13.39–17.25	4.79	6.85	11.64	10.25–13.03	p = 0.002*
#: HEC group versus OGOC (p value from Pearson’s χ² test).*: Statistical significance

Distribution of HPV genotypes according to cytology abnormalities

Figure 2 described the process by which we obtained our final results of cytology and histological abnormalities. Among the 3382 HPV positive women, 2414 was performed Thinprep cytologic test (TCT). And 171 women have been identified to be cytology abnormalities, accounting for 7.08%. The distribution of HPV genotypes in cytology abnormalities is showed in Table 4. Single-genotype infection is the main manner in all ASCUS (77/125, 61.60%), LSIL (22/37, 59.46%) and HSIL (1/1, 100%) group. As in AGC group, the single-genotype infection rate is 50% (4/4). The most common genotype is HPV 52 in ASCUS group, HPV 66 (21.62%) in LSIL group, HPV 58 (100%) in HSIL and AGC group. Prevalence of high-risk HPV is 70.40%, 78.38% and 100% in ASCUS, LSIL and HSIL respectively. The top three genotypes were HPV52, 16, 58 in ASCUS, HPV 66, 58/16/39, 52 in LSIL, HPV 58 in HSIL.

Table 4

Distribution of HPV genotypes according to cytology abnormalities
		ASCUS				LSIL			HSIL			AGC
		S% (n = 77)	M% (n = 48)	T% (n = 125)		S% (n = 22)	M% (n = 15)	T% (n = 37)	S% (n = 1)	M% (n = 0)	T% (n = 1)	S% (n = 4)	M% (n = 4)	T% (n = 8)
High Risk		81.41%				88.57%			100%			100%
16		12.80	9.60	22.40		8.11	10.81	18.92	0.00	0.00	0.00	12.50	0.00	12.50
18		0.00	2.40	2.40		5.41	8.11	13.51	0.00	0.00	0.00	0.00	12.50	12.50
31		1.60	0.00	1.60		2.70	5.41	8.11	0.00	0.00	0.00	0.00	0.00	0.00
33		4.00	5.60	9.60		2.70	5.41	8.11	0.00	0.00	0.00	12.50	12.50	25.00
35		0.80	0.00	0.80		0.00	5.41	5.41	0.00	0.00	0.00	0.00	0.00	0.00
39		2.40	4.80	7.20		2.70	16.22	18.92	0.00	0.00	0.00	0.00	12.50	12.50
45		0.00	0.80	0.80		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
51		0.80	6.40	7.20		2.70	0.00	2.70	0.00	0.00	0.00	0.00	37.50	37.50
52		14.40	15.20	29.60		2.70	13.51	16.22	0.00	0.00	0.00	0.00	0.00	0.00
53		1.60	6.40	8.00		5.41	8.11	13.51	0.00	0.00	0.00	0.00	0.00	0.00
56		2.40	4.80	7.20		2.70	8.11	10.81	0.00	0.00	0.00	0.00	0.00	0.00
58		8.80	12.80	21.60		8.11	10.81	18.92	100.00	0.00	100.00	25.00	25.00	50.00
59		0.80	0.80	1.60		0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00
66		0.00	6.40	6.40		13.51	8.11	21.62	0.00	0.00	0.00	0.00	0.00	0.00
68		1.60	1.60	3.20		0.00	5.41	5.41	0.00	0.00	0.00	0.00	0.00	0.00
Low Risk	18.59%				11.43%				0.00%			0.00%
6		2.40	3.20	5.60		0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00
11		2.40	2.40	4.80		2.70	2.70	5.41	0.00	0.00	0.00	0.00	0.00	0.00
42		0.00	0.00	0.00		0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00
43		0.00	1.60	1.60		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
44		0.80	2.40	3.20		0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
CP8304		4.00	10.40	14.40		0.00	13.51	13.51	0.00	0.00	0.00	0.00	0.00	0.00

Table 5

Distribution of HPV genotypes according to histological abnormalities
	CIN Ⅰ			CIN Ⅱ			CIN Ⅲ				CA
	S% (n = 21)	M% (n = 16)	T% (n = 37)	S% (n = 13)	M% (n = 4)	T% (n = 17)	S% (n = 2)	M% (n = 0)	T% (n = 2)		S% (n = 2)	M% (n = 1)	T% (n = 3)
High Risk	89.83%			96.30%			100%				100%
16	10.81	10.81	21.62	52.94	17.65	70.59	50.00	0.00	50.00		25.00	0.00	25.00
18	0.00	5.41	5.41	5.88	0.00	5.88	0.00	0.00	0.00		0.00	25.00	25.00
31	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
33	5.41	0.00	5.41	11.76	11.76	23.53	0.00	0.00	0.00		0.00	0.00	0.00
35	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
39	2.70	8.11	10.81	0.00	11.76	11.76	0.00	0.00	0.00		0.00	0.00	0.00
45	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
51	2.70	2.70	5.41	0.00	11.76	11.76	0.00	0.00	0.00		0.00	25.00	25.00
52	13.51	13.51	27.03	5.88	17.65	23.53	0.00	0.00	0.00		0.00	0.00	0.00
53	0.00	8.11	8.11	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
56	2.70	8.11	10.81	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
58	18.92	16.22	35.14	0.00	5.88	5.88	50.00	0.00	50.00		25.00	0.00	25.00
59	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
66	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
68	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
Low Risk	10.17%			3.70%			0.00%			0.00%
6	0.00	0.00	0.00	0.00	5.88	5.88	0.00	0.00	0.00		0.00	0.00	0.00
11	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
42	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
43	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
44	0.00	2.70	2.70	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00
CP8304	0.00	8.11	8.11	0.00	0.00	0.00	0.00	0.00	0.00		0.00	0.00	0.00

Distribution of HPV genotypes according to histological abnormalities

Among the 3382 HPV positive women, 318 was performed cervical biopsy, and 59 women have been identified to be histological abnormalities, accounting for 18.55%. The single-genotype infection is still the main manner in all CIN Ⅰ(21/37, 56.76%),CINⅡ (13/17, 76.47%), CIN Ⅲ (2/2, 100%) and CA (2/3, 66.67%) group. The most common genotype is HPV 58 (21.62%), 52(27.03%), 16(21.62%) in CIN Ⅰ group, HPV 16 (70.59%), 52/33(23.52%), 51/39(11.76%) in CINⅡgroup, HPV 58/16 (50%) in CIN Ⅲand HPV16/18/51/58 (25.00%)in CA group.

Prevalence of HPV infection change by year

In order to better understand the inspection and infection of HPV in the past three years, we analyzed the data by years. As shown in Fig. 3, the number of HPV detection is on the rise, especially in the OGOC group. Although the HPV infection rate of OGOC group reached a peak in 2016, there was no significant change of that for total population during 2015 to 2017.

The HPV infection prevalence vary considerably from geographically to populations. Globally, the highest HPV infection rate is Sub-Saharan (25.6%), South America (14.3%), Asia (8.7%), Europe (5.2%) of women with normal cytology, [6].Even within a country, the HPV infection rate varies., It is 28.4% in northeast china, 20.16% in south China and 14.2% in northwest China[13–15]. The prevalence of neighboring southwest provinces is 26.2% in Chonqing, 16.95% in Guizhou, 12.9% in Yunnan[16–18]. For Sichuan, the fourth largest population province located in southwestern China, several studies have investigated its HPV epidemiology and genotype distribution, but the HPV infection prevalence varies, ranging from 10.15–31.3% [7–12]. In our study, the HPV infection prevalence of the total population is 23.84%, which is basically consistent with the result of Li et al (24.1%)[12]. By further analyzing of population, we found HPV infection prevalence of HEC group is significantly lower than that of OGOC group, which is 15.29% and 37.62% respectively. Among the HPV studies related to Sichuan Province, there is only one focused on the HEC population, and the prevalence of HPV infection is 12.6%[9]. But this study only calculated the high-risk HPV, which may result in the lower prevalence rate than ours. For OGOC population, our prevalence rate is slightly higher than that of Zhu’s study (32.0%)[11]. Compared to other province of China, our result of HEC group is lower than that of Guangdong (17.25%) and Zhejiang (19.5%)[13, 19]. Our result of OGOC group is higher than that of Hubei (17.68%), Guangdong (20.16%) and Zhejiang (22.3%), but lower than that of Fujian (38.3%)[13, 20–22]. Thus, women in Sichuan area are facing with the great threat of HPV infection, especially the women undergoing gynecological clinical symptoms.

Concern to the age of infected women, we found prevalence of HPV infection reached a peak at 21–30 years and 41–50 years group. This double peak result also appeared in other area of China, such as Hangzhou and Chongqing[18, 21]. However, after dividing the population into different groups, we found the prevalence of HPV reached peak at 41–50 years group in HEC group, but at 21–30 years group in OGOC group. A possible explanation is young women have frequent sex and their immune systems are not sensitize to HPV infection, which result in a high infection rate in 21–30 years group. The high infection rate of 41–50 years group may due to reduced immune functions[21, 23, 24]. This double peak result remind women of 21–30 or 41–50 years old should pay more attention to the HPV infection.

In our study, among the HPV positive population, we demonstrated the single genotype infection was the most common form, accounted for 62.06% in total, 74.36% in HEC and 54.01% in OGOC HPV positive women. And the most genotype of coinfection is Septuple Infection. These results are basically consistence with data of Tao et al. [25].

According to HPV prevalence survey, the most prevalent genotype worldwide is HPV 16 (2.41%), followed by HPV 58 (1.25%) and 31(1.07%)[6]. However several studies have demonstrate than HPV16, 52, 58 is the major infection genotype in China[13, 20–22]. In our study, the three most prevalent HPV types were HPV 52 (5.02%), 58 (3.61%), and 16 (3.24%) in the total screening population. Among the HPV positive women, HPV 52 genotype is the most prevalent genotype in Sichuan area, which consist with the data of Li et al[12], a pattern that was also seen Yunnan and Guizhou Province. However, in a previous study about Sichuan, HPV 16 has been identified to be top prevalent genotype (19.4%)[25]. In this study, HPV 52 was the second with 17.0%.Even though there are some discrepant results, the most prevalent genotype in Sichuan area were HPV 58, 16, 52. Among the low-risk HPV genotypes, HPV CP8304 is the most prevalent genotype in both HEC and OGOC group, which is consistent with Le’s research[13]. In OGOC group, HPV 16, 18,6, 11 subtype detections were significantly higher than HEC group, and HPV 53 and CP8304 subtype detections were significantly lower than HEC group. This information may be meaningful for the generating strategies for both cervical cancer screening and vaccine exploitation.

Persistent infection of high-risk HPV is strong carcinogenic factor to induce cervical cancer. In present study, the prevalence of high-risk HPV is 81.41%, 88.57%, and 100% in ASCUS, LSIL and HSIL respectively. The top three genotypes were HPV52, 16, 58 in ASCUS, HPV 66, 58/16/39, 52 in LSIL, HPV 58 in HSIL. HPV 52, 58, 16 accounted for 41.84% of cytology abnormalities. These results is consistent with the data of He et al, except the HPV 66, 39 in LSIL, which may due to the bias of sample size[9].

Among histological abnormalities, the prevalence of high-risk HPV is 89.83%, 96.30%, 100%, and 100% in CIN Ⅰ, CINⅡ, CIN Ⅲ and CA. The top three genotype is HPV 58 (21.62%), 52(27.03%), 16(21.62%) in CIN Ⅰ group, HPV 16 (70.59%), 52/33(23.52%), 51/39(11.76%) in CINⅡgroup, HPV 58/16 (50%) in CIN Ⅲ and HPV16/18/51/58 (25.00%) in CA group. HPV 52, 58, 16 accounted for 56.52% of histological abnormalities, which was consistent with several studies that investigated the relationship between HPV genotype and histological abnormalities in Sichuan area. These studies demonstrated HPV 16, 58, 52 infection accounts for a large percentage of histological abnormalities [10, 11, 25] [26, 27].

HPV vaccines was introduced to China in 2017. The bivalent vaccine (Cervarix, targeted at HPV16/18) is available since August 2017, and the quadrivalent vaccine (Gardasil, targeted at HPV6/11/16/18) is available since December 2017 in Sichuan province[12]. Thus, our study is a survey before the mass use of HPV vaccine in Sichuan area. According to our study, these tow kind cannot provide enough protection because of the high prevalent of HPV 52, 58 genotype. Therefore, the nonavalent vaccine (Gardasil, targeted at HPV6/11/16/18/31/33/45/52/58) is more suitable for women of Sichuan province, which should be introduced as soon as possible. And according to He’s study, at least half women in western China are willing to take the HPV vaccine, which is beneficial to the prevention and treatment of HPV infection[28].

There are several limitations in this study. One is absence of data of other area in Sichuan province, which meant these results may not represent all women in Sichuan.. Second, detailed information of population was not available for us to evaluate the effect of these characteristics on the prevalence of HPV infection. And the case of cervical cytology or histology abnormalities is limited. Therefore, larger and prospective studies about the mechanism are also needed to validate our findings.

Women in Sichuan area are facing with the great threat of HPV infection, especially the women undergoing gynecological clinical symptoms. Women with an ages of 21 ~ 30 or 41 ~ 50 years old, should pay more attention to HPV infection. In HEC group, HPV 52/CP8303/58 are the most prevalent genotype, which in OGOC group is HPV 52/58/16. HPV 52/16/58 accounted for the majority of cytology and histological abnormalities. These data could provide a scientific basis for the prevention and control strategies of cervical cancer in Sichuan area.

AGC

Atypical gland cells, ASCUS:Atypical squamous cells of undetermined significance, CI:Confidence intervals, CIN:Cervical intraepithelial neoplasia, DNA:DeoxyriboNucleic Acid, HEC:Health Examination Center, HPV:Human papillomavirus, HR-HPV:High-risk HPV, HSIL:High-grade squamous intra epithelial lesion, ICC:Invasive cervical cancer, LR-HPV:Low-risk HPV, LSIL:Low-grade squamous intraepithelial lesion, NILM:Negative of intraepithelial lesion or malignancy, OGOC:Obstetrics and gynecology outpatient clinics, PCR:Polymerase chain reaction, TCT:Thinprep cytologic test.

Ethics approval and consent to participate
This study was approved by the Ethics Committee of Sichuan Provincial People’s Hospital (NO.2019-323).
Consent for publication
Not applicable.
Availability of data and materials
The datasets used and analyzed in this study are available from the corresponding author on reasonable request.
Competing interests
The authors declare that they have no competing interests.
Funding
1. The Scientific research project of Sichuan provincial health and Family Planning Commission (18PJ115) provided ideas for the direction of the topic and help for quality assessment.
2. The National Nature Science Foundation of China (NCFS No. 81860469) provided help for data analysis and language modification of the manuscript.
Authors' contributions
QL and JZ obtained funding and drafted the manuscript. JZ and JW designed the study and conducting of the survey. JW, NJ and QW performed the analysis and interpretation of the data. JZ and JW were the principal investigators, provided all facilities necessary to complete this work and was involved in editing the manuscript. All authors read and approved the final manuscript.
Acknowledgements
We thank Xiangqin Liu, Juan Long, Guo Huang, Xuexi Zeng for the HPV genotyping assistance. We thank pathology department of Sichuan Provincial People’s Hospital for their kind assistance in collecting data.

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Prevalence and genotype distribution of HPV and cervical pathological results in Sichuan Province, China: a three years surveys prior to mass HPV vaccination

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Journal Publication

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Abstract

Figures

Background

Methods

Study population and include criteria

Cervical sample collection

HPV DNA extraction and genotyping

Thin prep liquid-based cytology test

Histology diagnosis

Statistical analysis

Results

Prevalence of HPV infection in HEC and OGOC group

Prevalence of HPV grouped by age in study population

Prevalence of HPV single and multiple HPV genotypes infection

Prevalence of HPV genotypes in HPV-positive population

Distribution of HPV genotypes according to cytology abnormalities

Distribution of HPV genotypes according to histological abnormalities

Prevalence of HPV infection change by year

Discussion

Conclusions

Abbreviations

Declarations

References

Status:

Journal Publication

Version 1