To our knowledge, this is the first study that provides information on prevalence and predictors of use of liquid-based cytology (LBC) for cervical screening in an Australian setting. We used data from a state-based registry in which only a small proportion of women (<1%) chose not to disclose identifiable information. The study was also conducted in the context of a relatively high overall screening participation rate in NSW, in which 58.8% of women aged 20–69 years were screened every 2 years [13] and 71.2% every 3 years in 2007-8 [13]. We found that adjunctive uptake of LBC in NSW is high, at approximately 27-30%, but that the decision to use LBC depends strongly on a woman’s age and previous screening history, and use of the technology is increased in high socioeconomic status and urban groups. Therefore, the study demonstrates that uptake of LBC, to date, has not been comparable for all groups of women; these findings are relevant to considerations of equity when new technologies for cervical screening are made available.
It is notable that the observed pattern of LBC uptake with age, which peaks in women in their thirties and forties, to an extent mirrors patterns in overall screening participation which peaks in women in their thirties, forties and fifties [9, 13]. Screening participation has also been shown to depend on socioeconomic status and area of residence [9, 13]. Taken together with the current study, these findings suggest that some of the factors that influence women to participate in cervical screening might also be involved in the decision to use LBC. Such factors could be related to financial issues, access to screening services, or understanding of the benefits of cervical screening. We also found that use of LBC was more likely when the test provider was a specialist gynaecologist, even in a group of women selected to have a normal history for 5 years prior to the index test, and after adjusting for having an abnormal index smear (which may have prompted the specialist referral). It is possible that greater awareness about LBC technology amongst specialist providers is a factor in this finding; and it is possible that the medical practitioner’s recommendation is a factor in the woman's decision to use LBC. Overall, our findings appear broadly comparable to historical findings from the USA where the decision to use LBC as a direct replacement to cytology might have involved additional costs to the woman; in that country it has been found that women with more education or who were living in metropolitan areas were more likely to have LBC testing [16, 17].
Because cytology registers are configured at the state level, we were not able to analyse national data in the current study. The rates of LBC use in NSW will have a considerable influence on national rates since the population in NSW comprises approximately one third of the Australian population. However, our findings for prevalence of uptake are not likely to be generalisable to other states – for example, uptake in Victoria in 2011 was 4% overall (personal communication, A/Prof. Marion Saville), whereas to our knowledge, detailed information on levels of uptake in other states have not been reported. Probable differences in the overall levels of LBC uptake between states probably depend on a range of factors including availability of the technology through specific laboratories. Nevertheless, even though absolute rates of uptake in other states probably differ from that in NSW, our finding that certain factors seem to predispose women towards choosing LBC may have broader applicability.
It is important that our findings are set in context of the scale of the potential benefits to women of having LBC testing. The test sensitivities for conventional cytology and manually-read LBC for detection of biopsy-confirmed CIN2+ lesions are similar [3, 4], and there is no evidence, to our knowledge, to suggest that adjunctive testing per se, improves overall sensitivity. However, there is some initial evidence from two Australian studies that image-read LBC may deliver greater benefits in terms of test sensitivity [5, 6]. Although in this study we were unable to quantify the proportion of adjunctive tests in NSW involving image analysis of the slide (because this information is not recorded in the NSW PTR), it is likely that a very high proportion of tests since 2008 have involved imaging, because the two laboratories processing the largest volumes of cytology slides now routinely use the technology (personal communication. Prof. Annabelle Farnsworth).
Modelled analysis has previously predicted that under favourable assumptions about LBC test accuracy, if image-read LBC were to be introduced as a direct replacement to conventional cytology in Australia, 68 additional cervical cancer cases and 19 deaths would be prevented, but 26 additional treatments for high grade precancerous lesions would be required for each case prevented [4]. However, this balance of benefits and harms also depends on other factors such as the age range for screening and the screening interval, and is also likely to change over time due to the effects of HPV vaccination. The National HPV Vaccination Program, introduced in 2007, involves routine vaccination of 12–13 years old girls and a catch-up of girls and women aged 12–26 years which was conducted to 2009; there are already initial indications of a potentially vaccine-related drop in biopsy-confirmed CIN2+ rates in Australian females less than 18 years of age [18]. These changes are likely to have a rapid effect on the balance of benefits and harms (and cost-effectiveness) of using LBC technology.
The findings of our study are timely. They provide important context on current patterns of uptake of LBC, which is an important candidate technology for inclusion in the National Cervical Screening Program. The scope of the Renewal process also includes evaluation of HPV DNA testing both as a triage test for women with low grade cytological abnormalities, and as a primary screening test. Consideration of LBC as a direct replacement for conventional cytology within the national program will likely take into account the potential to perform HPV testing from the LBC sample, as well as the impact of screening interval and age range on the balance of benefits and harms associated with a move to LBC. This integrated evaluation of changes to screening technology, in context of other aspects of screening, seems warranted.
