記住我
In Dar-es-Salaam, recruitment was done at Ocean Road Cancer Institute (ORCI). This is the national cancer treatment center that provides cervical cancer screening to women from the general population. In Kilimanjaro, enrolment was done at Kilimanjaro Christian Medical centre (KCMC), a northern zone tertiary health facility serving a catchment area of approximately 15 million people, and at Mawenzi regional hospital, which is a regional hospital that provides cervical cancer screening services.
Data collection EnrolmentOverall, 4080 women aged 25-60 years, non-pregnant with no previous history of cervical lesions were enrolled between August 2015 and September 2016. Written consent was obtained from participants following a detailed narration of the risks and benefits of participating in the study while assuring confidentiality.
QuestionnaireTrained health care providers conducted a face-to-face interview using a structured questionnaire and obtained information on socio-demographic factors, and sexual-reproductive history from the participants.
HIV testWomen were voluntarily counselled to undergo testing for HIV, except the known HIV positive women. Venous blood from the index finger was tested using the HIV-1/2 test (www.alere.com), and a supplementary quick HIV-1/2 test (Abbott Laboratories) was performed as confirmatory of a positive result. Discordant results were confirmed using Unigold (Trinity Biotech). Gynaecological examinationThe trained health care providers also performed a gynaecological examination. Cervical specimens for cytology and HPV testing were obtained using ThinPrep Pap test plastic spatula and endo-cervical brush. Subsequently, visual inspection using acetic acid (VIA) was performed according to the guidelines for cervical cancer screening in recourse-limited settings [], i.e. women who screened positive by VIA were treated with either cryotherapy or conization and cervical biopsies were taken in those women who had obvious cervical lesions. HPV DNA testing and genotypingHPV DNA testing was done using the Hybrid Capture 2 (HC2) test (Qiagen, Hildesheim, Germany) with a HR cocktail probe. A test was considered positive if one or more of the 13 HR HPV types was found (HPV16,18,31,33,35,39,45,51,52,56,58,59,68) (threshold of 1.0 pg HPV DNA/ml, corresponding to 1.0 relative light unit coefficient). The HPV positive samples were genotyped using INNO-LiPA HPV Genotyping Extra (LiPA) (Innogenetics Inc, Gent, Belgium). Prior to this, DNA was isolated using a MagnaPure device (Roche Systems, Indianapolis, IN) for the 200µl of the remaining denatured products from the HC2 test.
The LiPA test is a line blot assay based on reverse hybridization principles. It is designed to detect 18 HR HPV and intermediate risk types (HPV 5, page 76,18,26,31,33,35,39,45,51,52,53,56,58,59,66,68,73,82) and 10 low-risk types (HPV 6,11,40,43,44,54,70,69,71,74) [20Xu L Padalko E Oštrbenk A Poljak M Arbyn M. Clinical Evaluation of INNO-LiPA HPV Genotyping EXTRA II Assay Using the VALGENT Framework.]. Follow-upAfter enrolment, women were asked to return for a follow-up examination after approximately 14 months. If the women did not attend follow-up visit within one month of their appointment, an active follow-up was initiated. Non-attendees were contacted by phone and encouraged to attend. If the woman agreed to participate but did not show up within two weeks of the phone call, she had a home-visit by an outreach nurse who encouraged the woman to attend. If the woman still did not attend, an outreach nurse visited her and conducted the follow-up visit at home, where the cervical specimen collection was done using self-sampling with an Evalyn brush (Evalyn® Brush - Rovers Medical Devices). The data collection described for the enrolment was repeated at the follow-up visit, except cytology, and HIV testing for those who were already HIV positive, and those where the cervical specimen was collected at home. Statistical analysisIn the present study, we focused on HR HPV types defined as types associated with cancer or probably associated with cancer by the International Agency for Research on Cancer (IARC) (group 1 and 2A) (HPV 16,18,31,33,35,39,45,51,52,56,58,59,68) [21IARC. Human papillomaviruses. Monograph 100B2011.
]. Acquisition was assessed in two ways. We estimated the overall acquisition of HR HPV for women who were HPV negative at enrolment and became HR HPV positive during follow-up. Type-specific acquisition was defined as detection of one or more HR HPV types not detected at enrolment. Incidence rates (acquisition of HPV) was estimated as the number of events divided by the person-years at risk. We examined the HR HPV incidence rate according to HIV status and age, and we also assessed the incidence of HR HPV (overall and type-specific) among HIV positive and HIV negative women.Finally, using a multivariable logistic regression analysis, we examined factors associated with acquisition of HR HPV among women who were HPV negative at enrolment. The analysis included the following a priori selected covariates as potentially correlated to acquisition based on the literature and availability: age, education, marital status, alcohol use, pregnancy, lifetime number of sexual partners, having a sex partner during follow-up, partner circumcision, history of genital warts, HIV status, CD4 count collected within 6 months after the HIV test, time between enrolment and follow-up visit, and cervical sampling method. The measure of association was odds ratio (OR) with 95% confidence interval (CI). Age and time between enrolment visit and the follow-up visit were always included in the model. Initially, we made a model only adjusted for age and time between enrolment visit and follow-up visit, and subsequently, we conducted an analysis where we additionally adjusted for HIV status, lifetime number of sex partners, and the cervical sampling method. These factors were selected a priori. All statistical analyses were carried out using STATA (version 15, Statacorp, College Station, TX).
RESULTSAmong the 4080 women enrolled in the study, 4043 were included in the baseline population (Fig. S1). A total of 238 were not eligible based on different criteria (Fig.S1) thus 3805 women were eligible for follow-up. Altogether, 3074 women (80.8%) attended the follow-up. Of these, 307 women had missing HPV results at either enrolment or at follow-up, leaving 2767 women with an HPV result at both examinations, and hence eligible for analysis. The HIV positivity rate was 15.1%. The median time between the two examinations was 17.3 months.
The HR HPV results (HC2) at enrolment and follow-up are displayed in Table 1. In the study population, 514 were HR HPV positive at enrolment (18.6%) and 227 women were positive at follow-up (Table 1). Among the women who were lost to follow-up, a slightly higher proportion were HR HPV positive at enrolment (22%) (data not shown) Altogether, 2253 women were HR HPV negative at enrolment and of these, 184 women tested HR HPV positive at the follow-up visit. This corresponds to an incidence rate of 54.5 (95% CI: 47.1-62.9) per 1000 person-years. The incidence rate was 75.2 (95% CI: 54.5-103.7) per 1000 person-years among HIV positive women and 50.9 per 1000 person-years (95% CI: 43.3-60.0) among HIV negative women.Table 1Distribution of study participants according to high-risk (HR) HPV status (Hybrid Capture 2) status at enrolment and at the follow-up visit
The incidence rate across age groups in relation to HIV status is shown in Fig. S2. Both HIV positive and HIV negative women had decreasing HPV incidence rates with increasing age, with the incidence being higher among HIV positive women in all age groups except among the youngest women (25-29 years), and the difference in incidence rate was largest in the oldest age group, where a slight increase was observed among HIV positive women. Among HIV positives, the incidence decreased to 42.8 per 1000 person-years (95% CI: 22.4-89.7) in 50-60 years old women, and the corresponding figure for HIV negative women was 23.1 per 1000 person-years (95% CI: 14.2-37.7).
The incidence rate of specific HR HPV types was also examined, both overall and according to HIV status (Table 2). In women acquiring a new specific HR HPV type among those initially negative for that particular type, the incidence rate per 1000 person-years was highest for HPV52 (12.5; 95% CI: 9.5-16.5) followed by HPV16 (6.9 95% CI: 4.8-10.1). The same pattern was seen among women who were initially HPV negative. When we stratified for HIV status, a similar picture was observed in HIV negative women, however, HPV16 (14.2 per 1000 person-years, 95% CI 6.8-29.8) was as commonly acquired as HPV52 among HIV positive women. In addition, there was a relatively higher rate of HPV45 and 58 among HIV positive women, whereas HPV35 only occurred among HIV negative women.Table 2Acquisition of specific high-risk (HR) human papillomavirus (HPV) types, overall and according to HIV status.
Table 3 describes the association between selected factors and HPV acquisition. When adjusting for age and time between the two examinations, single women had increased odds for acquisition compared to married/cohabiting women. Women with ≥ 9 partners had more than three times higher odds for acquisition than women with ≤ 1 partner. Further, HIV positivity and lower CD4 count were related to increased odds of acquiring HR HPV, and the same applied to self-collection of the cervical specimen compared to a health provider-collected sample. When also adjusting for lifetime number of partners, HIV status, and method of cervical sample collection, HIV positive women had significantly higher odds of acquiring HPV as compared to the HIV negative women (OR 1.7; 95% CI 1.2-2.6), and the association was particularly strong for decreasing CD4 count (OR 5.3; 95% CI 1.9-15.2 for CD4 ≤ 199). In this multivariable model, younger age age (OR 1.6; 95% CI 1.0-2.5; age 25-29 years versus age 35-39 years), multiple partners (OR 2.9; 95% CI 1.4-5.9; ≥ 9 partners versus ≤ 1 partner) and being single (OR 1.4; 95% CI 1.0-2.0) remained positively associated with acquisition. Moreover, longer duration between the two examinations and self-collection of the cervical sample still increased the odds of acquiring HR HPV.Table 3Association between selected factors and acquisition of high-risk (HR) human papillomavirus (HPV) among initially HR HPV negative women
DISCUSSIONIn this large cohort of Tanzanian women aged 25-60 years, the overall HR HPV incidence rate was 54.5 per 1000 person-years, and HPV52 and HPV16 were the most frequently acquired HPV types. HR HPV acquisition was higher among HIV positive (75.2 per 1000 person-years) than HIV negative women (50.9 per 1000 person-years). Additionally younger age, being single, and multiple sex partners increased the odds of HPV acquisition.
When comparing our findings to other studies, our overall incidence rate deviate to some degree. In a study from the United states among female online daters, who had the same overall age range (25-65 years) as women in our study, a higher HR HPV incidence rate was found (29.5 per 100 person-years) [22Winer RL Hughes JP Feng Q Stern JE Xi LF Koutsky LA. Incident Detection of High-Risk Human Papillomavirus Infections in a Cohort of High-Risk Women Aged 25-65 Years.]. However, the difference in findings may be due to these women being examined triannually and that the majority belonged to younger age group (25-34 years). Similarly, a study from Tanzania by Houlihan et al reported a HR HPV acquisition rate of 11.3 per 100 person-years among teenagers (15-16 years), who were followed quarterly over a time-period of 18 months [17Houlihan CF Baisley K Bravo IG Kapiga S de Sanjosé S Changalucha J et al.The Incidence of Human Papillomavirus in Tanzanian Adolescent Girls Before Reported Sexual Debut.].Our data demonstrate that the most commonly acquired HPV type was HPV52, followed by HPV16, HPV56, HPV58 and HPV35. The same acquisition patterns were found in HIV negative women whilst HPV16 was as commonly acquired as HPV52 and the relative importance of HPV45 and 58 increased among HIV positive women. Similar patterns have been described elsewhere for both incidence and prevalence of HPV in women from Africa [23Clifford GM, Goncalves MAG, Franceschi S, HPV, Aids HsgJ. Human papillomavirus types among women infected with HIV: a meta-analysis. 2006;20(18):2337-44.
, 24Veldhuijzen NJ Braunstein SL Vyankandondera J Ingabire C Ntirushwa J Kestelyn E et al.The epidemiology of human papillomavirus infection in HIV-positive and HIV-negative high-risk women in Kigali, Rwanda.]. The documented high incidence of especially HPV 52 and 58 in our study could support the introduction of the nonavalent HPV vaccine.Further, we found a higher HPV acquisition rate among younger women which gradually declined by age. This finding confirms previous studies [15Nielsen A Iftner T Munk C Kjaer SK. Acquisition of high-risk human papillomavirus infection in a population-based cohort of Danish women., 23Clifford GM, Goncalves MAG, Franceschi S, HPV, Aids HsgJ. Human papillomavirus types among women infected with HIV: a meta-analysis. 2006;20(18):2337-44.
, 25Ferris DG Brown DR Giuliano AR Myers E Joura EA Garland SM et al.Prevalence, incidence, and natural history of HPV infection in adult women ages 24 to 45 participating in a vaccine trial., 26Goodman MT Shvetsov YB McDuffie K Wilkens LR Zhu X Thompson PJ et al.Prevalence, acquisition, and clearance of cervical human papillomavirus infection among women with normal cytology: Hawaii Human Papillomavirus Cohort Study.] and may reflect both behavioural and biological factors. Young women may be exposed to HPV more often because of their sexual behaviour; however, the decreasing odds of HR HPV among older women persisted after adjustment for number of partners in the multivariable analysis, so this may not be the sole explanation. Another contributing factor could be that young women may be more vulnerable than older women because the transformation zone at that age is located on the ectocervix and thus probably more accessible for some HPV types [27Castle PE Jeronimo J Schiffman M Herrero R Rodríguez AC Bratti MC et al.Age-related changes of the cervix influence human papillomavirus type distribution.]. Some other studies have reported a bimodal HPV-age curve with a second peak of acquisition among older women, potentially related to senile cervical para-basal cell senescence promoting reactivation of latent HPV infection [14Muñoz N Méndez F Posso H Molano M van den Brule AJ Ronderos M et al.Incidence, duration, and determinants of cervical human papillomavirus infection in a cohort of Colombian women with normal cytological results.]. We observed a tendency towards such a second peak in HIV positive women.When focusing of lifestyle factors, an increasing number of lifetime sexual partners was associated with an increasing risk of HR HPV, however, we found no association with number of partners between the two examinations. The latter observation may partly reflect a re-activation of previous HR HPV exposure given the fact that acquisition among women with recent sexual partners was similar to that among women without recent partners. Further, circumcision of male partner has been suggested to prevent HPV transmission [22Winer RL Hughes JP Feng Q Stern JE Xi LF Koutsky LA. Incident Detection of High-Risk Human Papillomavirus Infections in a Cohort of High-Risk Women Aged 25-65 Years.,28Giuliano AR Nyitray AG Albero G. Male circumcision and HPV transmission to female partners.], and our results support this as we found decreased odds of HPV acquisition related to circumcision, although statistical significance was not achieved. Likewise, we found a tendency for increased odds of HR HPV acquisition and binge drinking, though the association was not statistically significant. This finding is in line with other studies, which have also found such an association with aspects of alcohol drinking [23Clifford GM, Goncalves MAG, Franceschi S, HPV, Aids HsgJ. Human papillomavirus types among women infected with HIV: a meta-analysis. 2006;20(18):2337-44.
]. This association has been hypothesized to be related to more risky sexual behaviour, but in the present study the association did not change after adjustment for age, lifetime number of sex partners, HIV status, time between enrolment and follow-up, and cervical sampling method. Whether there also exist a biological reason for the association between HR HPV acquisition and alcohol intake is unclear.HIV positive women had approximately two times higher odds of incident HR HPV compared to HIV negative women. This finding is supported by several studies documenting an increased incidence of HPV in individuals infected with HIV, independent of sexual behavior [12Strickler HD Burk RD Fazzari M Anastos K Minkoff H Massad LS et al.Natural history and possible reactivation of human papillomavirus in human immunodeficiency virus-positive women., 29Blitz S Baxter J Raboud J Walmsley S Rachlis A Smaill F et al.Evaluation of HIV and highly active antiretroviral therapy on the natural history of human papillomavirus infection and cervical cytopathologic findings in HIV-positive and high-risk HIV-negative women.]. HIV positives have an increased overexpression of HPV oncogenes (HPV E1 and L1) with decreased tissue resident T memory cells [30Mattapallil JJ Douek DC Hill B Nishimura Y Martin M Roederer M. Massive infection and loss of memory CD4+ T cells in multiple tissues during acute SIV infection.] and this may imply an increased risk of new HPV infections or reactivation of latent HPV infections. Reflecting the role of the immune system, women with lower CD4 count (≤ 199 cell/mm3) were approximately 2 times more likely to have an incident HPV infection during follow-up compared to those with higher CD4 count (>500cell/ mm3). Based on this finding, close CD4 monitoring combined with early ART initiation and sustained adherence is recommended as it will support immune system recovery and reduce HR HPV associated morbidity among HIV positive women. The preventive effect of such an approach has been documented in a recent meta-analysis, where women living with HIV on ART had a lower prevalence of both HR HPV and CIN2+ lesions [31Kelly H Weiss HA Benavente Y de Sanjose S Mayaud P. Association of antiretroviral therapy with high-risk human papillomavirus, cervical intraepithelial neoplasia, and invasive cervical cancer in women living with HIV: a systematic review and meta-analysis.]. Particularly in LMIC, where a substantial HIV-attributable cervical cancer burden has added to the existing burden of cervical cancer, women may benefit from close CD4 monitoring and early initiation of ART.Strengths of the present study include the large sample size and a high proportion of the eligible women participating in follow-up (>80%). Furthermore, we included a high number of HIV positive women, making it possible to estimate HR HPV incidence rates, both overall and type specific and according to HIV status with reasonable power. Some limitations were inherent in this study. We only had two measurements of HPV with a median time between the examinations of around 17 months, and thus we might have missed infections acquired and cleared between the visits, thereby underestimating the incidence of HR HPV. In addition, even though we had a large study, the numbers were still small in some analyses. Further, we cannot rule out reporting bias, as some of the sex-related questions in the questionnaire were potentially sensitive. This may have hampered our ability to adequately adjust for sexual behaviour and thus residual confounding is likely. Finally, we were not able to retrieve details of HIV-related factors, such as type of ART treatment, duration of treatment, and HIV viral load. This has limited our ability to conduct analyses involving HIV immunologic markers and treatment.
In conclusion, HPV52 was the most frequently acquired HPV type, followed by HPV16, HPV56, HPV58, and HPV35. The pattern differed slightly by HIV status, with HPV 16 being more incident in HIV positive women. Young age, increasing number of lifetime partners, being single, and HIV positivity were associated with increased odds of HPV acquisition, and HIV positive women with low CD4 count had especially increased odds of HPV acquisition. Given the described risk factors for HPV acquisition, measures to address sexual risk-taking behaviour and efforts to improve the immune status among HIV positive women have a potential to decrease HPV acquisition. In order to overcome the cervical cancer burden in Tanzania, prophylactic vaccination against HPV – preferably with the nonavalent vaccine – is important. Finally, continuation of cervical cancer screening programs with special focus on HIV positive women is also still important.
留言 (0)