Cervical cancer remains to be a global public health concern, as there were 569,847 new cases and 311,365 deaths worldwide, ranking the fourth most common cancer in women [1]. The annual incident and death cases of cervical cancer estimated in China were 98,900 and 30,500 [2]. Routine screening for cervical cancer was a major prevention strategy to attain dramatic reductions in incidence and mortality, of which cytology, human papillomavirus (HPV) DNA-based testing, and visual inspection with acetic acid (VIA) or Lugol’s iodine (VILI) were recommended methods [3,4]. The Chinese government had launched the National Cervical Cancer Screening Program (NCCSP) to provide free screening services since 2009; however, it only targeted on women in rural areas [5]. Past epidemiologic studies suggested that only one-fifth of adult women in China announced having ever been screened [6,7]. Thus, it is deeply in need to discover vulnerable individuals who had never receive screening, to ensure suitable screening related services delivery and achieve high participation rate.

Shenzhen is one of the economically prosperous cities in China, with a majority of internal migrants lacking the local household registration but seeking jobs to settle down here every year. It was estimated of more than 7,860,000 migrants living in this city by the end of 2010 [8]. Migrants were thought to be a disadvantaged group for their shortage in socioeconomic characteristics when compared with local residents. Moreover, they might not have equality to share public resources and health services depending on household registration status to great extent. It was reported that migrants were provided with less satisfied quality of the primary health care than their local counterparts [9]. Migrants might also own poorer health literacy in cervical cancer prevention. For example, significant inequalities existed in understanding the role of HPV in cervical cancer and attitudes towards HPV vaccination between female migrants and natives in Shenzhen [10]. Nevertheless, whether migrants performed as well as local residents in the participation and willingness to have cervical cancer screening was still unclear and of great urgency to be explored.

In 2009, cervical cancer prevention has been included in a public welfare project of maternity and child healthcare by the local government in Shenzhen, and was implemented with financial support in all administrative districts [11]. Cervical cancer prevention-related work were carried out every year, including health education to the public, technical training to medical professionals on screening, diagnosis and treatment, and free organized screening services. In order to explore the positive influence on female migrants by this prevention project, we conducted two citywide surveys on cervical cancer screening participation and willingness to screen in 2011 and 2014, respectively. This study attempted to detect 3-year changes of screening rate and willingness to screen among female migrants, as well as associated demographic factors, and finally to help differentially target priority groups to improve screening compliance.

Our study demonstrated increased screening rates of cervical cancer among female migrants from 2011 (25.8%) to 2014 (35.1%) in Shenzhen, which was relatively higher than the rate (21.4%) from a nationwide survey conducted in 31 provinces of mainland China [7]. These above-mentioned rates were still much lower than those in Hong Kong Chinese women (80.8%) [12,13], suggesting that women’s screening participation might be affected by distinct socioeconomic levels across developed and undeveloped regions. We then observed that the willingness to screen of female migrants remained stable in last 3 years, but tended to be in a relatively high level when compared to previous surveys targeted different female groups in other cities (ranged from 63.3% to 85.0%) [14–17]. Hence, identifying barriers to get female migrants screened is urgently in need to be involved in cervical cancer prevention network of Shenzhen city, and the target of health education work should be placed on translating attitude or belief into practice according to the health belief model [18].

For the majority of whom were unwilling to participate in screening, we found their main concerns focused on the screening cost, lack of spare time, and ignorance on screening necessity. These barriers towards screening in Shenzhen (a first-tier city) were quite different from those in rural areas, for example, most women in Wufeng (a typical low-income county located in central China) worried about anxious feeling of disease diagnosis and did not receive screening because of not symptoms/discomfort [15]. In addition, age and in-school status might also influence on women’s consciousness about screening services. A population-based survey in Hong Kong reported that for both school girls and young out-school females, the most common reason for no intention to participation was having a limited knowledge of cervical screening, including “Never heard about it” and “Do not know its function”, moreover, out-school females were more likely to concern about the screening cost than school girls [19]. We further found that self-paying willingness to screen did increase over time in our study. The potential reason lied that the income levels of migrants have been improved from 2011 to 2014. The expected price of self-paying screening did also elevate, as we observed a greater proportion of women selecting higher screening price in 2014. Nevertheless, establishing a nationwide or regional cervical cancer screening program for free or low-priced is in demand, since financial concerns to screening remained to be a barrier among nearly two-fifths of migrant women in our study.

Socio-demographic factors that were considered to influence women on their practice in cervical cancer prevention in past studies, were also identified in our study, such as age, marital status, education, income, employment, and medical insurance [7,13,20,21]. We found that women aged 41 or older had a higher odds of receiving screening when referred to 30 years or younger. An older age might associate with a higher possibility of gynecologic problems, subsequently visiting related clinics and receiving screening services incidentally. This association could be reversed when women were out of the recommended age range for cervical screening, as the screening participation would be inhibited with aging process [13]. We also found that married women participated in screening practices more actively than single individuals. On one side, it perhaps resulted from more frequent sexual behaviors and fertility needs engaged in marriage. Sexual behaviors have been shown to influence women’s attitudes towards screening substantially [19], to some extent, it might waken women to involve in routine gynecologic related examinations. On the other side, single but sexual active women might underestimate their risk of cervical cancer and present low screening attendance [13]. Furthermore, our study suggested that well-educated, employed, wealthy, and insured women were more readily to undergo or accept screening. As implied in previous investigations, a good socio-demographic status could promote women to obtain more knowledge of cervical cancer prevention and making accurate decisions, to be well-resourced in affording screening costs, and to increase the probability of opportunistic screening owing to higher reimbursement [7]. These findings suggested that the accessibility of cervical screening should be improved among women with poor socio-demographic status. Developing an outreach, low-cost, and easily accessible screening and treatment method could be helpful to screening promotion, as Zhao et al. [22] did in rural China.

Although we did not detect variation of willingness to screen in the present study, the screening rate did increase from 2011 to 2014, more interestingly, the associated demographic factors with screening participation and willingness also changed. As mentioned previously, women in Shenzhen could get access to screening services with two choices: free organized screening services provided by the government from 2009, and opportunistic self-paying screening services available in local gynecology clinics [23]. Women who met the following conditions were available to receive free organized screening services: aged from 30 to 59 years old, sexually active, with a household registration of Shenzhen city or stayed in Shenzhen for more than six months, and did not receive free screening services within recent three years. There were two candidate screening methods [3] (cytology alone every 3 years, or HPV and cytology “Co-testing” every 5 years) for free, varied by the difference of financial support across districts. There were some possible reasons why female migrants participate in screening more actively by years. For one thing, women might own more deposits with the increased income [24], which might facilitate them to engage in opportunistic screening. For another thing, the local government enlarged the financial support on organized screening with the growth of gross domestic product in these years [24], so that women could gain more free quotas to being screened. Moreover, we observed that the impact of education level on screening participation was weakened in 2014 than that in 2011, while the association between education and screening willingness did not change significantly. These findings possibly suggested limited effects of education on screening practice promotion over time. Regard to screening willingness, even if it did not increase significantly, the self-paying willingness was improved in three years, suggesting that women might concern less about the cost in opportunistic screening due to the increased income. Therefore, women’s screening willingness was shown to be weakly affected by income level in 2014 than in 2011. A reverse finding was shown in the impact of medical insurance on screening willingness, which was more apparent in 2014 rather than in 2011, probably because of increasing reimbursement in accessing screening services. In addition, we noticed that women with an advanced age exhibited less screening willingness. One potential explanation raised by other researchers was that women might feel no necessity to participate in screening after the menopause, which further impaired their risk perception and willingness [13]. Nonetheless, future studies should consider varied predictors of screening practices among elderly women who were still at risk of the disease.

Some limitations should be clarified. First, for self-reported surveys rather than medical records, response or recall bias could not be excluded. Second, we did not collect information on sexual behaviors and HPV vaccinated status, leaving restriction to draw any conclusion about the impact of these important factors on screening uptake. We also did not distinguish between organized and opportunistic screening, in which distinct participations probably existed. Prospective studies with long follow-up periods are clearly needed to verify vital predictors of screening uptake. Third, as there were no nationwide screening programs for urban areas, findings from Shenzhen city might not be generalized to represent the screening situation of female migrants across the whole country, but to provide novel insights in cervical cancer prevention work in other developed cities. Furthermore, due to the huge difference in sample size of two surveys, it is hard to tell if the observed differences come from the effect of policy or just because of difference population. However, the sampling survey sites and the recruitment of study subjects in 2014 were the same as those in 2011. The investigation processes of these two surveys were consistent with each other. It would be acceptable to clarify the study objectives by adopting a multistage random cluster sampling method. Even though the different sample sizes restricted us to draw confirmed conclusions, some associated clues were detected from this study. Researches that enroll the same study subjects with the longitudinal follow-up design will be ideally appropriate in further verification explorations.

In summary, we investigated the three-year changes of cervical cancer screening rate and willingness among female migrants in Shenzhen city through two citywide surveys. Despite of health resources devoted in cervical cancer prevention by the government in recent years, there were at least three-quarters of female migrants who had never been screened. We also identified changes of associated socio-demographic characteristics that influence women’s engagement in screening practices. Proper and targeted actions should be taken and adjusted regularly with a priority in promoting cervical cancer screening participation.