Taking it to their doorstep: outreach well-woman clinics in brothels for cervical cancer screening of female sex workers in North-Western Nigeria
How common are dangerous HPV infections and early cervical cancer signs among sex workers in Northwest Nigeria, and what puts them at higher risk?
Abstract
Background
Female sex workers (FSWs) are at increased risk for HPV, precancerous lesions, and cervical cancer (CaCx), yet they tend to be screened at lower rates than other women. However, data on the prevalence of high-risk HPV (hrHPV) and cervical cytological abnormalities among FSWs are limited in Nigeria, with no data available from North-western Nigeria. This study aimed to assess the prevalence of HPV 16 and 18 infections and cervical cytological abnormalities among FSWs in Sokoto State, and to identify factors associated with HPV 16/18 infection among this vulnerable group.
Methods
This cross-sectional study involved 165 FSWs who were recruited during outreach well-woman clinics conducted in brothels. After obtaining informed consent, data were obtained through a structured questionnaire administered by interviewers, followed by cervical smear collection. Liquid-based cytology (LBC) and real-time PCR testing for HPV DNA were performed on the samples. Binary logistic regression was applied to explore potential predictors of HPV 16/18 infection.
Results
The majority of respondents (119; 72.9%) consented to CaCx screening. Over half (65; 54.6%) tested positive for HPV 16/18. Single HPV 16 infection (34; 28.6%) was twice as common as single HPV 18 infection (17; 14.3%), while 14 respondents (11.8%) had co-infection. Cervical cytological abnormalities were detected in 10 participants (8.4%), predominantly low-grade squamous intraepithelial lesions (LSIL), which comprised 90% of the abnormalities. HPV 16/18 prevalence was highest in the 30–39 age group (23; 42.6%), while abnormal cytology occurred exclusively in the 21–39 age groups at similar rates. In bivariate analysis, age at coitarche, age at first marriage, and years engaged in sex work were significantly associated with HPV infection. However, only years engaged in sex work remained a significant predictor of HPV 16/18 infection in regression analysis (aOR = 5.13; 95% CI: 1.53–17.22; p = 0.008).
Conclusion
HPV 16/18 infection were highly prevalent among respondents, despite a relatively low prevalence of cervical cytological abnormalities. These findings highlight the potential benefit of the bivalent HPV vaccine in Sokoto State. Regular CaCx screening is strongly recommended for FSWs, even after they disengage from sex work. Further research with a larger sample size and comprehensive testing for all high-risk HPV genotypes is recommended.
Frequently Asked Questions: A Deep Dive into a Nigerian Study on HPV and Cervical Cancer Risk
What is Human Papillomavirus (HPV) and how is it related to cervical cancer?
Human Papillomavirus (HPV) is one of the most widespread sexually transmitted infections (STIs) globally. While most HPV infections are harmless and clear up on their own, persistent infection with certain "high-risk" types of the virus is the primary cause of cervical cancer. According to scientific consensus, persistent high-risk HPV (hrHPV) infection is responsible for approximately 95% of all cervical cancer cases.
Which HPV types are the most dangerous?
Globally, the two most common and dangerous high-risk HPV types are HPV 16 and HPV 18. Together, these two strains are linked to an estimated 70% of all cases of invasive cervical cancer worldwide, making them the primary targets for vaccination and screening efforts.
Why was this study focused on female sex workers in Nigeria?
This study specifically focused on female sex workers (FSWs) for several critical public health reasons:
- Vulnerability: FSWs are recognized as a vulnerable group with a significantly higher risk of contracting HPV and other STIs compared to the general female population.
- Data Gap: Before this study, there was limited data on the prevalence of high-risk HPV among FSWs in North-western Nigeria.
- Regional Health Burden: This data gap existed despite cervical cancer being the second leading malignancy affecting women in the region (Sokoto State), making it a major local health issue.
What was the main finding regarding HPV infection in the study?
The study revealed a very high prevalence of high-risk HPV among the participants. The headline finding was that over half of the screened participants (54.6%) tested positive for the high-risk HPV types 16 and/or 18. The research further specified that a single infection with HPV 16 was twice as common as a single infection with HPV 18.
If HPV rates were high, did the study also find a high rate of cervical abnormalities?
No, and this is one of the study's most important nuances. Despite the high prevalence of high-risk HPV, the rate of cervical cytological abnormalities (changes in cervical cells that can be precursors to cancer) was relatively low. These abnormalities were detected in only 8.4% of participants. The vast majority of these were classified as low-grade squamous intraepithelial lesions (LSIL), which are considered early-stage, mild cellular changes. However, the study also found one case of a high-grade squamous intraepithelial lesion (HSIL), which represents more significant, pre-cancerous changes.
How can HPV prevalence be high while cervical abnormalities are low?
The researchers highlight two key factors that explain this apparent discrepancy:
- Age and Natural Clearance: The majority of the study participants were young women. In this demographic, an estimated 80-90% of HPV infections clear up naturally within two years without causing any lasting harm.
- Long Progression Time: For the small percentage of infections that do persist, the natural progression from a high-risk HPV infection to cervical precancer or invasive cancer is a very slow process, typically taking between 15 to 20 years. Therefore, an active infection today may not result in cellular abnormalities for many years.
What was the single biggest risk factor for HPV infection identified in this group?
After analyzing numerous factors, the final regression analysis identified only one statistically significant predictor for HPV 16/18 infection: the number of years engaged in sex work.
Specifically, individuals who had been in sex work for one year or less were approximately five times more likely to be infected with HPV 16/18 compared to those who had been in sex work for two years or more. The study authors hypothesize that this could be because newer FSWs may have less knowledge of safe sex practices, while more experienced individuals may have developed better protective strategies.
What are the limitations of this study?
Understanding a study's limitations is crucial for interpreting its findings. The authors noted three key limitations for this research:
- Small Sample Size: The study involved a relatively small number of participants, which reduces its statistical power. This means some real associations might have been missed, and the wide confidence intervals around some results indicate a degree of uncertainty.
- Limited HPV Testing: Due to funding constraints, the study only tested for HPV 16 and 18, not the full range of high-risk HPV types. This is significant because the researchers noted that other HPV genotypes could be responsible for some of the cervical abnormalities they observed.
- Self-Reporting Bias: Data on behaviors like condom use and client numbers relied on participants' self-reports, which can be influenced by a desire to provide socially acceptable answers and may not be completely accurate.
Why is studying HPV in a group like female sex workers important for the general population?
Research in key populations like FSWs has broader public health implications. The study explains that FSWs can be central to the transmission of STIs, including HPV. The men they serve may act as "bridges" for transmission into the wider community through their stable or marital partners. Consequently, understanding the specific HPV genotypes circulating among FSWs can provide a valuable reflection of the types that are also circulating in the general female population.
What screening methods does this research suggest are most effective?
The study's findings underscore the value of a combined screening approach. The authors recommend pairing HPV DNA testing with traditional cytology (like a Pap smear). The rationale is that each test has unique strengths:
- HPV DNA Testing: Highly sensitive and better at predicting a woman's future risk of developing significant cervical disease.
- Cytology: Highly specific, meaning it is very good at confirming the presence of existing cellular abnormalities.
Using these two methods together improves overall disease detection and provides a negative predictive value approaching 100%, offering the highest level of assurance.
What are the key takeaways from this research for preventing cervical cancer?
The study provides several critical insights that can inform public health strategies for cervical cancer prevention.
- High HPV Burden: The research confirms a substantial burden of high-risk HPV among FSWs, reinforcing the urgent need for targeted screening programs and prevention efforts for this vulnerable population.
- Vaccine Value: The finding that HPV 16 and 18 are the predominant high-risk types in this group strongly supports the potential benefit of HPV vaccines, such as the bivalent vaccine (Cervarix), that specifically protect against these strains.
- Long-Term Screening: Because cervical cancer can take 15-20 years to develop after an initial infection, the study strongly recommends regular cervical cancer screening for high-risk individuals, even long after they are no longer active in high-risk environments.