Christou et al. BMC Public Health 2010, 10:373 http://www.biomedcentral.com/1471-2458/10/373 nominated GP (if one has been nominated). For positive tests, a letter advises participants to visit their GP to dis- cuss a follow-up procedure, namely colonoscopy. A bowel cancer screening register has been established within Medicare to assist in follow-up of those with positive tests not undergoing colonoscopies, rescreening of participants, and to aid data collection, monitoring and evaluation [9]. The data obtained are collected via forms filled in by the individual, their GP, colonoscopist and others involved. As completion of the forms is not compulsory, a large amount of information is incom- plete or missing [25]. The sensitivity and specificity of FOBT varies by test type and manufacturer. Sensitivity is in the order of 60- 85% for iFOBTs when used regularly within a program, although with once-off testing this drops to 30-50% [48]. The iFOBT (MagStream 1000/Hem SP) currently used in the Australian program has a sensitivity of 66% for cancer and 20% for polyps over 1 cm [50-52]. Hence, many false positives occur, resulting in high numbers of follow-up colonoscopies. Of those who have a positive FOBT, about 5-10% will have CRC, and 20- 35% will have an adenoma identified [41]. Test out- comes and the ability of the test to identify CRC are not usually fully understood or made apparent to the public, yet are important when weighing up the risks and bene- fits associated with participation in the program [53]. In 2009, nearly half a million testing kits were recalled and the program was temporarily suspended for six months after an unusual decline in the number of posi- tive test results, assumed to be due to faulty kits. Test- ing resumed in November 2009 with a new kit that was initially distributed to re-screen those who received the faulty kits [54]. However, the new kit is recommended for use only up to 30 degrees Celsius creating potential problems for many regions, particularly in the north of Australia where a large proportion of Indigenous people reside. The new screening kit will not be sent to these regions initially, creating even further inequities in access. Much greater thought and effort needs to be put into the problem of differential access to the program. 1.3 Indigenous participation and test profile - results of National Bowel Cancer Screening Program monitoring reports, 2006-2008 Adequate levels of participation are essential for the success of a screening program in reducing mortality from CRC and for population benefit equating to that attained in randomized controlled trials [8]. It is also an important contributor to the cost-effectiveness of the program in terms of number of lives saved and costs saved by averting a cancer diagnosis [8,55]. Mon- itoring reports completed in 2007, 2008 and 2009 details performance of the program from 2006-2008 [10,25,56]. Page 6 of 21 Overall participation in the Australian NBCSP was 37.6% by the end of 2008 however, participation was lower than that observed during the pilot (45.4%). The average positivity rate was 6.6%, significantly higher among men than women which is reflected in higher incidence rates [25]. Table 1 details variation in partici- pation, positivity rate and proportion of correctly com- pleted tests according to demographic factors. Analyses up until mid-2008 showed Indigenous parti- cipation was 17% - less than half the non-Indigenous rate [10]. In the 2009 monitoring report which docu- mented results from 2008 only, Indigenous people were 2.2 times less likely than non-Indigenous to participate in the screening program [25]. However, Indigenous identification of participants in the program was through self-report and was completed by only 63% of participants. Another important finding from the 2008 report was that Indigenous people were significantly less likely to complete the FOBT correctly, with Indigenous females aged over 65 years having the lowest rate of correctly completed tests [10]. Indigenous people also had higher FOBT positivity rates although this was not significant due to the small sample size [25]. The pro- portion of correctly completed tests was also signifi- cantly lower for people who nominated a language other than English as their preferred language [10]. Significant differences were also observed according to geographic location, with inner regional areas having the highest rates of participation while those in remote and very remote areas (where 26% of Indigenous Australians reside) were significantly less likely to participate. Parti- cipation also fell with lower SES [10], and those in the most disadvantaged lowest quintile of the population were significantly less likely to follow up a positive result with their GP. Indigenous Australians are disproportio- nately represented in this quintile. Substantial numbers of unreturned health provider forms make it impossible to determine how many Indi- genous (or other) people with positive FOBTs went on to complete a colonoscopy. For the entire program, only 42% of participants with a positive FOBT had a colono- scopy recorded. The remaining participants either did not have a colonoscopy or the colonoscopy report was not returned [25]. Lack of quality surveillance informa- tion compromises the assessment of actual population benefits and the impact on the incidence and mortality from CRC, particularly on population subgroups. Despite this, a recent analysis by Ananda et al [57] assessing the initial impact of the NBCSP from mid 2006 to mid-2008, reported its success in identifying CRC at an earlier stage. This study utilised linked data from hospitals across Australia to gather information on CRC cases reported by surgeons and found that 40% of cancers identified through the NBCSP (N = 40) were at