In this study high age, low education, being widowed/separated, being married at a young age and being of high parity were associated with VIA positivity. Screening attendance was associated with being aged above 35, having no formal education and being HIV positive.
To our knowledge this is the first epidemiological study which has attempted to elicit risk factors for VIA positivity and screening attendance in Tanzania. Several factors may have affected the validity of the study findings and whether the sample of unscreened women can be considered a representative sub sample of the target group of women, who had never attended screening, may be questioned. However, to avoid selection bias and to assure as high representativity as possible, cluster randomisation was used to recruit women who had never participated in the screening program. When focusing on the screened women, the subsample appeared to be older than the full screened population. This may have biased the findings and resulted in an overestimation of the association between high age and screening attendance.
The VIA positivity rate among the 14,107 women screened at ORCI during the period 2002–2008 was 7%. In other cross-sectional studies, the proportion of VIA positive women varies from 2% to 16%
[7, 14, 15]. It has been suggested that this observed heterogeneity in VIA positivity rates may be due to factors other than disease prevalence
. Hence, when discussing the validity of VIA as a screening method for cervical cancer there is concern about a lack of standardized test definition, differences in test providers skills, underlying prevalence of other sexually transmitted infections and lack of uniformity in the application of gold standard for disease definition
. These considerations should be taken into account in the interpretation of the VIA positivity rate reported in the present study.
VIA positivity was significantly correlated with being widowed/separated, being of high parity, being married at a young age and being of low education. Women who are separated or widowed may have higher number of lifetime sexual partners in comparison with married women and as number of lifetime sexual partners increases the risk of HPV infection they are more susceptible for developing precancerous lesions
. High parity is another well-known risk factor for precancerous lesions
, this association is most likely due to repeated cervical trauma during consecutive births and hormonal adjustment during and after pregnancies which may create an entry point for the HPV virus. The found association between marriage at a young age and VIA positivity is consistent with a Nigerian study where marriage at early age was reported to be a risk factor for being VIA positive
. In line with this, a pooled analysis of case–control studies from eight developing countries have documented that early age at first sexual intercourse and early pregnancy are risk factors for cervical cancer
. The study further documented that the reported age at first sexual intercourse and age at first marriage correlated for 92% of the women
. These findings support a hypothesis that early age sexual intercourse is a risk factor for invasive cervical carcinoma. This hypothesis is further supported by a study conducted among married adolescent girls in urban centers in Kenya and Zambia which found that early marriage increases coital frequency, decreases condom use and virtually eliminates girls' ability to abstain from sex
. Furthermore, for women in some parts of the world, the behavior that puts them at risk of HIV infection and most likely HR-HPV infection is unprotected sex within marriage
. Although married girls are less likely than single girls to have multiple partners, this protective behavior may be outweighed by their greater exposure via unprotected sex with partners who have higher rates of infection, or if their husband has unprotected sex with other partners. Finally, the found association between VIA positivity and poor education may be explained by the fact that women who have not attended school are less informed about safe sex and condom use and are thereby at increased risk of acquiring a sexual transmitted infection, including HR-HPV infection.
In a low income setting, it may be argued that women who are widowed/separated, women who are having many children and women who are poorly educated share in common that they are at greater risk of being in a financial constraint situation and this may influence their health seeking behavior. A situation which together with the fact that they are at increased risk of HR-HPV infection place them at double jeopardy for developing cervical cancer. The association between low socioeconomic position and risk of developing cervical cancer has also been documented in a meta-analysis based on 57 studies
. The pooled analysis of the included studies found an increased risk of approximately 100% between high and low social classes for the development of invasive cervical cancer and an increased risk of approximately 60% for cervical dysplasia and carcinoma in situ. The increased risk was apparent in all regions, although it was stronger in America, Asia and Africa than in Europe.
HIV status was found to be significantly associated with screening attendance. Hence women who were HIV positive were more likely to participate in the screening program than HIV negative women were. This finding reflects the existence of a referral linkage between the HIV care and treatment program and the cervical cancer screening program in Dar es Salaam, where women who are tested HIV positive are encouraged to be screened for cervical cancer. The fact that HIV-infected women are more often infected with HR-HPV compared to HIV-uninfected women documents the need of such linkage. Based on our findings it may be argued that in countries with high HIV prevalence, the integration of cervical cancer into HIV care and treatment provides an ideal platform to reach HIV positive women who are at increased risk of developing cervical cancer. The cost effectiveness of this approach has also been documented in a Zambian study which showed that such integration allowed early detection of cervical cancer in HIV-infected women
An association between HR-HPV infection and HIV infection was found. As the study design was cross sectional, it is not possible to determine whether the women acquired the HPV or the HIV infection first. One explanation behind the found association may be that HIV positive women are less likely to clear an HPV infection
[9, 26, 27] and are more susceptibility to infection with multiple types of HPV
[28–30]. In addition, it has also been suggested that HIV may be activating a dormant HPV infection and thus increase the risk of HPV-related disease