[Show abstract][Hide abstract] ABSTRACT: Concerns have been raised that the proportion of cervical cancer preventable by human papillomavirus (HPV) 16/18 vaccines might be lower in sub-Saharan Africa than elsewhere.
In order to study the relative carcinogenicity of HPV types in Nigeria, as well as to estimate the vaccine-preventable proportion of invasive cervical cancer (ICC) in the country, we compared HPV type prevalence among 932 women from the general population of Ibadan, Nigeria, with that among a series of 75 ICC cases diagnosed in the same city. For all samples, a GP5+/6+ PCR based assay was used for the detection of 44 genital HPV types.
In the general population, 245 (26.3%, 95% confidence interval (CI) 23.5% - 29.2%) women were HPV-positive, among whom the prevalence of HPV35 and HPV16 were equally frequent (12.2%, 95% CI 8.4% - 17.0%). In ICC, however, HPV16 predominated strongly (67.6% of 68 HPV-positive cases), with the next most common types being 18 (10.3%, 95% CI 4.2% - 20.1%), 35, 45 and 56 (each 5.9%, 95% CI 1.6% - 14.4%). Comparing among HPV-positive women only, HPV16 and 18 were over-represented in ICC versus the general population (prevalence ratios 5.52, 95% CI 3.7 - 8.3 and 1.4, 95% CI 0.6 - 3.3, respectively). Other high-risk HPV types, as well as low-risk and multiple HPV infections were less common in HPV-positive women with ICC than from the general population.
Our study confirms that in Nigeria, as elsewhere, women infected with HPV16 and 18 are at higher risk of developing ICC than those infected with other high-risk types, and that current HPV16/18 vaccines have enormous potential to reduce cervical cancer in the region.
Full-text · Article · Dec 2010 · Infectious Agents and Cancer
[Show abstract][Hide abstract] ABSTRACT: Few human papillomavirus (HPV) seroprevalence studies have been carried out in women from low-resource countries.
Seroprevalence of antibodies against HPV16 and HPV18 was assessed in 7,074 women ≥15 years of age (median 44 years) from eight world areas. Serum antibodies against HPV16 and HPV18 were tested for using enzyme-linked immunosorbent assay. HPV DNA was assessed using a general primer GP5+/6+-mediated PCR.
HPV16 and HPV18 seroprevalence both ranged from <1% (Hanoi, Vietnam) to >or=25% (Nigeria). Of women who were HPV16 or HPV18 DNA-positive, seropositivity for the same type was 39.8% and 23.2%, respectively. Seropositivity for either type was directly associated with markers of sexual behavior. HPV16 and/or 18 (HPV16/18)-seropositive women had an increased risk of having cytologic abnormalities only if they were also HPV DNA-positive. A high international correlation was found between HPV16/18 seroprevalence and overall HPV DNA prevalence (r = 0.81; P = 0.022). However, HPV16/18 seroprevalence was substantially higher than the corresponding DNA prevalence in all study areas (although to different extents) and, contrary to DNA, tended to increase from young to middle age, and then decline or remain fairly constant. In all study areas, the vast majority of the information on the burden of exposure to HPV16/18 derived from serology.
The correlation between HPV DNA and HPV serology was not very good at an individual woman level, but high at a population level.
HPV serology is a poor marker of current infection or related lesions, but it can contribute, together with DNA, in evaluating the variations in the burden of HPV infection worldwide.
[Show abstract][Hide abstract] ABSTRACT: Smoking increases the risk of squamous-cell carcinoma of the cervix, but it is not clear whether smoking increases the risk of acquisition or persistence of human papillomavirus (HPV) infection.
Information on smoking was collected from 10 areas in four continents among population-based, age-stratified random samples of women aged 15 years or older. HPV testing was performed using PCR-based enzyme immunoassay. Unconditional logistic regression was used to estimate odds ratios (OR) and corresponding 95% confidence intervals (CI) of being HPV-positive by smoking habits, adjusted for age and lifetime number of sexual partners.
Ten thousand five hundred and seventy-seven women (mean age 41.4 years) were included. Among current smokers, the risk of being HPV-positive increased with smoking intensity, after allowing for lifetime number of sexual partners: ORs for <5, 5-14 and >/=15 cigarettes per day were 1.21 (95% CI 0.95-1.54), 1.39 (95% CI 1.04-1.87) and 2.01 (95% CI 1.32-3.08), respectively, as compared with never-smokers. The risk among former smokers (OR = 0.95, 95% CI 0.73-1.23) was similar to that among never-smokers. Analyses stratified by lifetime number of sexual partners showed a significant trend in risk only for women with one lifetime sexual partner.
Our study suggests that current, though not former, smoking is associated with an increased prevalence of HPV, after allowance for sexual covariates. Among current smokers, HPV prevalence increased with smoking intensity, but a clear dose-response relationship was exclusively seen among women who declared one lifetime sexual partner.
Full-text · Article · Jul 2008 · International Journal of Epidemiology
[Show abstract][Hide abstract] ABSTRACT: Better information on the prevalence of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infection is needed in many world areas.
Cross-sectional study of population-based samples of nonpregnant women aged 15 to 44 years in Nigeria, Colombia, Argentina, Vietnam (2 areas), China, Thailand (2 areas), Korea, and Spain. 5,328 consenting women aged 15 to 44 years participated. Exfoliated cervical cells were collected and testing for CT and NG and human papillomavirus (HPV) was done using PCR-based assays.
Age-standardized CT prevalence ranged between 0.2% (95% confidence interval, CI: 0.0-0.7%) in Spain and 5.6% (95% CI: 3.4-7.8%) in Nigeria. NG ranged between 0% (with broad CIs) in several areas and 2.6% (95% CI: 1.0-4.2%) in Nigeria. Prevalence of CT in all areas combined was greater in women aged 15 to 24 (4.5; 95% CI: 3.4-5.8%) than 25 to 44 (2.6; 95% CI: 2.1-3.1%), whereas NG prevalence was similar in the 2 age groups (0.3%). The only significant risk factors were NG infection (for CT), CT infection (for NG) and infection with high-risk HPV types (for both).
The prevalence of CT and, most notably, NG was relatively low in a variety of countries. Our findings, however, do not apply to subsets of high-risk women who are likely to be underrepresented in our population-based samples.
[Show abstract][Hide abstract] ABSTRACT: An inverse relationship between age and human papillomavirus (HPV) prevalence has been reported in many developed countries, but information on this relationship is scarce in many other parts of the world. We carried out a cross-sectional study of sexually active women from the general population of 15 areas in 4 continents. Similar standardised protocols for women's enrolment, cervical specimen collection and PCR-based assays for HPV testing were used. HPV prevalence in different age groups was compared by study area. 18,498 women aged 15-74 years were included. Age-standardised HPV prevalence varied more than 10-fold between populations, as did the shape of age-specific curves. HPV prevalence peaked below age 25 or 35, and declined with age in Italy, the Netherlands, Spain, Argentina, Korea and in Lampang, Thailand and Ho Chi Minh, Vietnam. This was not the case in Songkla, Thailand nor Hanoi, Vietnam, where HPV prevalence was low in all age groups. In Chile, Colombia and Mexico, a second peak of HPV prevalence was detected among older women. In the poorest study areas in Asia (Shanxi, China and Dindigul, India), and in Nigeria, HPV prevalence was high across all age groups. The substantial differences observed in age-specific curves of HPV prevalence between populations may have a variety of explanations. These differences, however, underline that great caution should be used in inferring the natural history of HPV from age-specific prevalences.
Full-text · Article · Dec 2006 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: High parity, early age at first full-term pregnancy (FTP), and long-term oral contraceptive (OC) use increase cervical cancer risk, but it is unclear whether these variables are also associated with increased risk of acquisition and persistence of human papillomavirus (HPV) infection, the main cause of cervical cancer. Information on reproductive and menstrual characteristics and OC use were collected from 14 areas worldwide, among population-based, age-stratified random samples of women aged 15 years or older. HPV testing was done using PCR-based enzyme immunoassay. Unconditional logistic regression was used to estimate the odds ratios (OR) of being HPV-positive according to reproductive and menstrual factors and corresponding 95% confidence intervals (CI). When more than two groups were compared, floating CIs (FCI) were estimated. A total of 15,145 women (mean age, 40.9 years) were analyzed. Women with >or=5 FTPs (OR, 0.90; 95% FCI, 0.76-1.06) showed a similar risk of being HPV-positive compared with women with only one FTP (OR, 1.00; 95% FCI, 0.86-1.16). However, nulliparous women showed an OR of 1.40 (95% CI, 1.16-1.69) compared with parous women. Early age at first FTP was not significantly related to HPV positivity. HPV positivity was similar for women who reported >or=10 years of use of OCs (OR, 1.16; 95% FCI, 0.85-1.58) and never users of OCs (OR, 1.00; 95% FCI, 0.90-1.12). Our study suggests, therefore, that high parity, early age at first FTP, and long-term OC use are not associated with HPV prevalence, but rather these factors might be involved in the transition from HPV infection to neoplastic cervical lesions.
Full-text · Article · Nov 2006 · Cancer Epidemiology Biomarkers & Prevention
[Show abstract][Hide abstract] ABSTRACT: Human papillomavirus (HPV) is a sexually transmitted infection but it is unclear whether differences in transmission efficacy exist between individual HPV types. Information on sexual behavior was collected from 11 areas in four continents among population-based, age-stratified random samples of women of ages > or = 15 years. HPV testing was done using PCR-based enzyme immunoassay. Unconditional logistic regression was used to estimate odds ratios (OR) of being HPV positive and corresponding 95% confidence intervals (95% CI). Variables were analyzed categorically. When more than two groups were compared, floating confidence intervals were estimated by treating ORs as floating absolute risks. A total of 11,337 women (mean age, 41.9 years) were available. We confirmed that lifetime number of sexual partners is associated with HPV positivity (OR for > or = 2 versus 1, 1.86; 95% CI, 1.63-2.11) but the association was not a linear one for HPV18, 31, and 33 (i.e., no clear increase for > or = 3 versus 2 sexual partners). Women who had multiple-type infection and high-risk HPV type infection reported a statistically nonsignificant higher number of sexual partners than women who had single-type and low-risk type infections, respectively. Early age at sexual debut was not significantly related to HPV positivity. Husband's extramarital sexual relationships were associated with an OR of 1.45 (95% CI, 1.24-1.70) for HPV positivity in their wives after adjustment for age and lifetime number of women's sexual partners. We did not observe a significant association with condom use. Our study showed an effect of both women's and their husbands' sexual behavior on HPV positivity. Furthermore, it suggests some differences in the pattern of the association between sexual behavior and different HPV types.
Full-text · Article · Mar 2006 · Cancer Epidemiology Biomarkers & Prevention