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Bowel cancer is the third most common cancer in the United Kingdom The WritePass Journal
Bowel cancer is the third most common cancer in the United Kingdom Introduction Bowel cancer is the third most common cancer in the United Kingdom IntroductionReferences Related Introduction Bowel cancer is the third most common cancer in the United Kingdom with approximately 35,000 new cases diagnosed each year.Ã 1 in 16 men and 1 in 20 women will develop colorectal cancer at some point in their lives. It is also the second most common cause of cancer death, with just over 16,000 (approximately 9,000 men and 7,000 women) deaths per year (ONS, 2010) Incidence rates for colorectal cancer increased by 28 per cent for men and 11 per cent for women between 1971 and 2007. Ã Rates peaked at 57 per 100,000 in men in 1999 and 38 per 100,000 women in 1992. In the ten year period from 1998 to 2007, incidence rates for men and women have remained relatively stable (ONS 2010). Being overweight, having an inactive lifestyle and a low fibre diet can increase the risk of colorectal cancer. Eating red and processed meat, and insufficient amounts of fruit and vegetables, smoking and drinking excess alcohol are contributing factors. People with CrohnÃ¢â¬â¢s disease in the colon, ulcerative colitis, polyps in the colon or a family history of colorectal cancer may also be at an increased risk (Department of Health, 2000). More than four out of every five new cases of colorectal cancer are diagnosed in people aged 60 and over, with most cases presenting in the 70-79 age group in men and in the 75 and over age group in women (ONS, 2010). Survival from cancers of the colon and rectum has doubled in 30 years.Ã For colon cancer, five-year survival was 50% for men and 51% for women diagnosed in 2001-2006 and followed up to 2007.Ã Five-year survival for those diagnosed in 1971-1975 and followed up to 1995 was 22 per cent for men and 23 per cent for women (Rachet et al 2009). Differences in survival rates are based on how early, or at what Ã¢â¬ËstageÃ¢â¬â¢, a patient presents for treatment.Ã This Ã¢â¬ËstagingÃ¢â¬â¢ is a method (first developed in 1932) of evaluating the progress of the cancer in a patient. The classification considers the extent to which the cancer has spread to other parts of the body. Once established, the best course of treatment is then decided.Ã There are currently for categories: Dukes Stage A: The tumour penetrates into the mucosa of the bowel wall but no further Dukes Stage B: The tumour penetrates into, but not through the muscularis propria (the muscular layer) of the bowel wall. Dukes Stage C: The tumour penetrates into, but not through the muscularis propria of the bowel wall; there is pathologic evidence of colon cancer in the lymph nodes. C2: tumour penetrates into and through the muscularis propria of the bowel wall; there is pathologic evidence of colon cancer in the lymph nodes. Dukes Stage D: The tumour, which has spread beyond the confines of the lymph nodes (to organs such as the liver, lung or bone). Five year survival rates according to the DukesÃ¢â¬â¢ stage of classification are: Ã DukesÃ¢â¬â¢ Stage A 85Ã¢â¬â95%, B 60Ã¢â¬â80%, C 30Ã¢â¬â60%, D less than 10%.Ã These significant differences in survival rates were the basis for the introduction of a national screening programme for bowel cancer (Rachet et al 2009). The NHS Bowel Cancer Screening Programme in England began in July 2006, as part of the NHS National Cancer Plan (2000).Ã Patients aged between 60-69 were initially offered screening every two years and people 70 and over could request it via their GP. The criteria has since changed (from January 2010) with screening now offered to those aged 70-75 years. The objective of bowel screening is to detect bowel cancer at an early stage and get these identified patients into an appropriate treatment pathway. Ã The screening programme can also detect polyps, which, although are not cancers they may develop into cancers over time. They can easily be removed which reduces the risk of bowel cancer developing. This essay outlines the process of the UK bowel screening programme and from this provides a critical analysis of the test, performance and cost-effectiveness leading to a broader discussion considering Ã whether to implement the screening programme in relation to UK NSC criteria. Description and critical analysis of the evidence about the test performance (15 marks) Screening is defined by Raffle Gray (2007) as; Ã¢â¬ËThe systematic application of a test, or inquiry, to identify individuals at sufficient risk of a specific disorder to warrant further investigation or direct preventive action, amongst persons who have not sought medical attention on account of symptoms of that disorder.Ã¢â¬â¢ There is a distinct difference between screening and case finding (e.g. NHS Health Check) In clinical practice, patients approach healthcare professionals to ask for medical advice and help, in contrast with screening programmes, where professionals actively encourage people to undergo an investigation on the basis that it may benefit them. The performance of a screening programme is based on its Ã¢â¬ËsensitivityÃ¢â¬â¢ and Ã¢â¬ËspecificityÃ¢â¬â¢.Ã The sensitivity of a screening test is the percentage of the screened population that has the disease and tests positive. Ã For instance, a sensitivity of 70% means that for every ten participants with the disease, seven will test positive and the other three will be false negatives. Ã A test with poor sensitivity results in a high percentage of the population with the disease escaping detection. These people will be falsely reassured and could delay presenting important symptoms. The specificity of a test is the percentage of the screened population that is disease free and also tests negative. For instance, a specificity of 80% means that eight out of ten people who do not have the disease will have a negative result. Two out of ten will have a false positive result and require further assessment before the possibility of disease can be eliminated. Ã A test with poor specificity will have an important effect for the individual, including increased anxiety and unnecessary clinical follow up. The ideal screening test would have a high sensitivity (to reduce the number of false negatives) and a high specificity (to reduce the number of false positives). It is usually difficult to achieve this as there is a trade off between the two measures; limiting the criteria for one results in a decrease in the other. Another key feature of a screening test is the predictive value for which there are two key aspects. The positive predictive value (PPV) of a test is the percentage of people who test positive who have the disease. The negative predictive value is the percentage of those who test negative who are disease free. The predictive value is influenced by both the sensitivity and specificity of the test, as well as the prevalence of the condition being screened for. In the UK the screening test used for the bowel screening programme is the Ã¢â¬â¢faecal occult blood testÃ¢â¬â¢ (FOBT).Ã In terms of operational delivery there are approximately 20 Hubs across the country responsible for coordinating the screening programme, each Hub sends out letters of invitation to the eligible population, explaining about bowel cancer screening.Ã Ã Standard practice ensures that within a week of receiving a letter a FOBT kit will be sent to patients.Ã The kits are used by the patient, samples taken and returned to the Hub, who then send normal results to individuals, and inform GPs via a standards letter.Ã For positive tests, the Hub contacts the individual directly, and an appointment is them made for the patient to have further investigations (colonoscopy) with the commissioned provider of colonoscopy services. The test and the framework for its operational delivery are based on a number of large scale trials which were undertaken to assess whether FOB testing of asymptomatic people could be useful in detecting individuals with early bowel cancer the largest trial conducted in Nottingham. The trials and the subsequent UK pilots (2008) found: uptake of approximately 60%, subsequent pilots returned a lower uptake which decreased with deprivation sensitivity was approximately 60% for cancer and 80% for adenomas biannual testing was as effective as annual testing screening of asymptomatic 55-75-year-olds reduced mortality from bowel cancer by 16% Ã overall, or by 25% in those 60% of individuals who return an FOBT there was no reduction in all-cause mortality from FOB screening. These results meant that FOBT can detect 60% of all colon cancers.Ã Alternatively, this also means that 40% are not routinely detected.Ã This lower sensitivity rate is a trade off based on the fact that FOBT screening is non-invasive, easily performed without the need for bowel preparation, and can be performed on transported specimens and of low cost.Ã A higher sensitivity rate could be achieved through once-only flexible sigmoidoscopy screening in prevention of colorectal cancer but uptake, patient acceptability and cost would be a barrier to population roll-out. Description and critical analysis of the evidence about the cost-effectiveness (15 marks) There are a number of research publications that compare specific models of bowel screening through the application of different these will be described, but from a public health perspective, this essay will also consider the wider opportunity cost in relation to bowel screening. Agreement relating to how cost-effective an intervention is depends on what the intervention is being compared against. For instance, a starting point in the evaluation of the UK pilot for Bowel Screening Cost-effectiveness (2003) states Ã¢â¬ËAnalysis found that the cost-effectiveness of a national programme compared well with other forms of cancer screening such as breast and cervical cancer screening.Ã¢â¬â¢ This statement is all about comparison with associated interventions that are deemed reasonable and safe with a generally fair return on investment this is more about acceptable levels of investment producing acceptable levels of return compared to similar interventions of the same type rather than considering whether the programme can be delivered more efficiently or could the resource be allocated in a different way to achieve the desired results. The issue of whether the programme could be delivered more cost effectively has been reviewed in a number of publications (Allison et al. 2006.Ã Rozen et al. 2000.Ã Levin et al 1997). Ã These comparisons have, in particular, considered the merits of; FOBT alone, flexible sigmoidoscopy and FOBT combined, and one-off colonoscopy with cost-effectiveness more often defined as the cost per cancer death prevented.Ã Of all the screening tests, FOBT alone prevents fewer cancer deaths than the other interventions, but the addition of a flexible sigmoidoscopy to the FOBT increases the rate of cancer prevention. One-off colonoscopy has the greatest impact on colorectal cancer mortality. Ã Although purported to be the most cost effective the outcomes are all based on clinical outcome alone but when considering cost FOBT returns better broader population results (in terms of patient acceptability and absolute cost to deliver) than any other of the interventions outlined. One of the most popular measures of cost effectiveness is considered through estimating the lifetime NHS costs and potential health benefits (defined as cost per QALY quality-adjusted life-years).Ã For bowel screening this equates to comparing the population not offered screening but treated according to current practice compared with a sample of the population who are offered screening as per the protocol used in the pilot study.Ã The cost per QALY is the additional costs of screening, after allowing for treatment cost savings, and the gain in survival and quality of life. The problem with QALYs has always been the question of what is the upper limit on what society is prepared to pay for health gains. Ã Ã The National Institute for Clinical Excellence (NICE) provides some limited information about upper limits in this context. Ã It has been suggested that Ã £30,000 per QALY might represent an acceptable threshold (NICE, 2008).Ã Studies (Young et al, 2005. Lieberman, 2005. Khandker RZ, 2000) have returned a cost per QALY for bowel screening of between Ã £2,000 to Ã £3,000 which is well within the acceptable cost guidance offered through NICE but this does not mean that it is the more cost effective or efficient way of delivering the service. Raffle Gray (2007) touch on the issue of broader public health view and the influence of single issue groups, they outlined that; Ã¢â¬ËIf information for policy making is to serve the health needs of the public to best effect, then it must enable policy makers to keep a sense of perspective and context.Ã Doing this requires policy questions that are concerned with whole programmes of care, not just the single issue being considered.Ã¢â¬â¢ If we consider this in the context of a UK bowel screening programme costing Ã £50 million per year can we justify its delivery on the associated reduction in mortality of up to 16%? On face value, it seems we can (e.g. economic analysis and QALY returns etc) but that is assuming 60% uptake.Ã PCTs in the West Midlands are currently delivering the programme at between 28% and 42% uptake. As public health policy makers at what point do we consider the low uptake at sustained high cost as a reasonable return on investment?Ã There may be a greater return on investment if the Ã £50 million was invested in broader public health programmes targeted at reducing the population risks by changing behaviour (e.g. smoking cessation, diet, exercise). Taking this even further, could we reinvest the total Ã £50 million in another, unrelated, public health issue such as falls prevention programmes and tackle the risk factors associated with bowel cancer through legislation and regulation (e.g. increased taxation of tobacco or introducing a more challenging approach to price per unit for alcohol)?Ã In the long term, this may have more effect on a population effect on bowel cancer mortality at a lower cost. Description and analysis of the ethical issues associated with implementing this screening programme including accessibility, equity, the balance of harm and good and informed choice (15 marks) The benefits of bowel screening include a modest reduction in colorectal cancer mortality and a possible reduction in cancer incidence through the detection and removal of colorectal adenomas.Ã These benefits need to balanced against the potential harm of the programme.Ã One of these identified harms is the psycho-social consequences of receiving a false-positive result or a false-negative result, the possibility of over diagnosis (leading to unnecessary investigations or treatment) and the complications associated with treatment. Another key possible harm relates to the possibility of bowel perforation for those patients who have with a positive FOBT and require further investigation. Ã The UK National Bowel Cancer Screening evaluation (2003) suggested a perforation rate of 1 in 1500 colonoscopies.Ã This compares well with other bowel screening programmes in Australia and France which have returned a rate of 0.96 per 1000 procedures .Ã Following a diagnosis of perforation, most patients (over 90%) require surgery, and a significant number (30%) require colostomy or ileostomy. From a health inequalities viewpoint there are a number of issues relating to accessibility and equity that are cause for concern.Ã The first of these is the issues of uptake in the context of deprivation. Data for 2004-2008 shows us that there is a 11% of higher incidence rate of colon cancer for males in the most deprived population compared with the least deprived population (ONS 2008). This can be compared with uptake of screening which has demonstrated that males and younger age groups have lower uptake rates (Weller et al, 2007).Ã In the long term this pattern has the potential to further increase inequalities in health. There is also strong evidence that suggests certain ethnic sub-groups have lower participation rates of bowel screening than the general population (Robb et al, 2008; Szczepura et al, 2008). The reasons for these differences are complex ranging from health beliefs, misunderstanding and cultural attitudes. This defined lack of uptake by ethnic group is not evident in all screening programmes, for example, South Asian women are significantly less likely to undertake bowel screening compared to breast screeningÃ (29% compared to 49%)Ã (Price et al. 2010).Ã This suggests more research needs to be undertaken to try and understand the key factors involved. Literacy can also be linked to deprivation and ethnicity and is a critical factor in participation in colorectal cancer screening. Ã As with many screening programmes a great deal of resource has been allocated to producing information and materials for the bowel cancer screening programmes Ã¢â¬â but we know that health literacy varies a great deal in the population (Von Wagner et al, 2009), and many patients will have limited comprehension of the material provided. Equity of access to diagnostic services is also a possible issue to manage. For two of the hospitals participating in the UK bowel screening pilot, there were significant differences between waiting times for colonoscopy for screened and symptomatic patients. For example, in Scotland the average waiting times for pilot patients was between 2 and 7 weeks, whereas for symptomatic patients they rose from around 10 weeks to between 16 and 20 weeks within the first year of the Pilot (Scottish Executive Health department 2006). Description of how to implement programme quality assurance and an assessment of the practical issues with implementation (15 marks) There are a number of frameworks for assessing and assuring the quality of healthcare service.Ã Examples include DemingÃ¢â¬â¢s 14 principles of management and DonabedianÃ¢â¬â¢s seven components of quality.Ã Raffle and Gray build in these two models and advocate six key points in applying quality assurance to screening. These are; Defining the objectives of the programme in a way that encapsulates what a Ã¢â¬ËgoodÃ¢â¬â¢ screening programme will look like. Devise ways of measuring quality that will ensure these objectives are met. Set standards for each measurement; this is a subjectively chosen level that you will want the programme to achieve. Give responsibility to the local programmes for monitoring, how well they are doing in meeting the standards, and for working to improve quality in meeting those standards. Collate information about performance against standards and publications nationally for all the local programmes Provide support mechanisms for overseeing quality and for assisting local programmes with training and quality improvement. One way of doing this is by creating regional quality assurance teams. From personal experience, working with breast screening a cervical screening programmes, the need for clear standards and an overarching review process (the support mechanism) is essential. Ã A Ã¢â¬Ëdeep diveÃ¢â¬â¢ approach to some of the key performance indicators is also very useful.Ã For example, if the target for local uptake is 60% a PCT, with the help of public health team, should approach this in terms of ensuring this uptake is achieved within the hardest to reach populations. In terms of the practical issues of implementation issues such as ease of completing the kit can be an important factor in determining uptake (The UK CRC Screening Pilot Evaluation Team, 2003). Ã Uptake can also be greatly affected by simple mistakes in postal address Ã¢â¬âso intended recipients do not receive the testing kit. This is one of the biggest factors associated with the uptake of an Australian trail where 20% of respondents in an Australian study claimed that they had not completed a FOB test because it had never been received in the post (Worthley at el., 2006). The Australian study also identified a preference by patients for increased GP involvement or promotion in the bowel cancer screening procedure (Salkeld et al., 2003; Worthley et al., 2006). Ã Many patient may prefer to have been offered screening through their GP, while almost half of those patients suggesting an alternative method of invitation wanted greater GP involvement (Worthley et al., 2006). Ã Similar evidence findings have emerged in the US, where a physicianÃ¢â¬â¢s recommendation has been cited as the Ã¢â¬Ëstrongest predictorÃ¢â¬â¢ of compliance with screening among men and women (Rabeneck, p. 1736, 2007). Overall discussion and conclusions about whether to implement the screening programme in light of the considerations already discussed and the UK NSC criteria (20 marks) Evidence suggests there is a reduction in colorectal cancer mortality as a result of introducing the UK bowel screening programme.Ã Following the national evaluation, it is also indicated that there was a beneficial shift towards identifying colorectal cancer at an earlier stage (e.g. Dukes Stage A).Ã Other benefits of screening that were not explored in this essay include the reduction in colorectal cancer incidence through detection and removal of colorectal adenomas, and potentially, less invasive treatment of identified early-stage colorectal cancers. These outcomes alone may be justification enough to continue to implement the programme in the UK. Several important additional areas require further research when deciding whether to continue with the programme or not. First, there is limited information currently available concerning the information needs and psychosocial consequences of screening for colorectal cancer. Ã Secondly, there is limited research on patient acceptance of colorectal cancer screening or on how best to involve particular socio-economic or ethnic groups who, as outlined previously, are often under-represented in uptake. Thirdly, the accuracy of other methods of the faecal occult blood test (e.g. RHNA) for colorectal cancer screening also requires further investigation. Maybe conclusions could be drawn through assessing the programme against the The UK NSC criteria which are considered below. NSC criteria states that all the cost-effective primary prevention interventions should have been implemented as far as practicable before consideration is given to proceed with the screening programme. This has not been the case in the UK. As outlined in this essay, greater effort could have been made to tackle the population risk factors before decision on implementing a Ã £50 million programme.Ã The screening programme could also be seen to negate the need for individuals to take responsibility for lifestyle behaviour and the risks associated with colorectal cancer. In terms of Ã¢â¬ËThe testÃ¢â¬â¢, it is simple, safe, precise and validated as per NSC guidance, and is generally acceptable in the population. Although, the essay has outlined the differences in uptake by socio-economic group and ethnicity. When considering Ã¢â¬ËThe TreatmentÃ¢â¬â¢, there are effective treatments for patients identified through early detection, and this evidence has shown to lead to better outcomes than late treatment. The Screening Programme is based on good evidence from high quality Randomised Controlled Trials that the screening programme is effective in reducing mortality or morbidity and there is evidence that it is Ã clinically, socially and ethically acceptable to health professionals and the public. The benefits from the screening programme also outweigh the physical and psychological harm (caused by the test, diagnostic procedures and treatment).Ã The opportunity cost of the screening programme resource has been touched upon in this essay. The view is that all other options for managing the condition have not been fully considered, particularly primary prevention. Overall, the national bowel screening programme does provide a population drop in mortality.Ã The programme follows NSC guidance which is a benchmark for acceptability and although this essay supports the programme there still needs to be some further research undertaken in relation to uptake for specific population groups and the opportunity cost of the investment. References Allison, J., M. Tekawa, et al. (1996). A comparison of faecal occult-blood test for colorectal cancer screening. NEJM 334: 155-9. Donabedian, A. (1990), The seven pillars of qualityÃ¢â¬â¢Ã¢â¬â¢, Archives of Pathology and Laboratory Medicine, Vol. 114, pp. 1115-18. Hardcastle JD, Chamberlain JO, Robinson MHE, Moss SM, Amar SS, Balfour TW et al. Randomised controlled trial of faecal occult blood screening for colorectal cancer. Lancet 1996, 348; 1472-1477 Hoff G, Bretthauer M (2008) Appointments timed in proximity to annual milestones and compliance with screening: randomised controlled trial. Br Med J 337: 2794 Khandker RZ, Dulski JD, Kilpatrick JB, Ellis RP, Mitchell JB, Baine WB: A decision model and cost-effectiveness analysis of colorectal cancer screening and surveillance guildelines for average-risk adults. Int J Tech Assess in Health Care 2000, 16;3:799-810. Kronborg O, Fenger C, Olsen J, Jorgensen OD, Sondergaard O. Randomised study of screening for colorectal cancer with faecal occult blood test. Lancet 1996; 348; 1467-1471 Levin, B., K. Hess, et al. (1997). Screening for colorectal cancer: a comparison of 3 faecal occult blood tests. Archives of Internal Medicine 157(9): 970-7. Lieberman DA: Cost-effectiveness model for colon cancer screening. Gastroenterology 1995, 109:1781-90. Mandel JS, Bond JH, Church JR, Snover DC, Bradley GM, Schuman LM et al. Reducing mortality from colorectal cancer by screening for faecal occult blood. N Engl J Med 1993; 328; 1365-1371 National Institute for Health and Clinical Excellence. 2007/042a updated. Ã NICE responds to judicial review outcome. NCIN, Cancer Incidence by Deprivation England, 1995-2004. 2008. NHS MEL(1998)62. Screening for Colorectal Cancer Office for National Statistics. 2010. statistics.gov.uk/sdataset.asp?9091 Price et al. 2010) BMC Health Services Research 2010, 10:103 biomedcentral.com/1472-6963/10/103 Rachet, B., et al., Population-based cancer survival trends in England and Wales up to 2007:an assessment of the NHS cancer plan for England The Lancet Oncology (2009). Raffle A, Gray M. Screening; Evidence and Practice, Oxford University Press, 2007. Rozen, P., J. Knaani, et al. (2000). Comparative screening with a sensitive guaiac and specific immunochemical occult blood test in an endoscopic study. Cancer 89: 45-52. Robb KA, Power E, Atkin W, Wardle J (2008) Ethnic differences in participation in flexible sigmoidoscopy screening in the UK. J Med Screen 15: 130Ã¢â¬â136 Salkeld, G., Solomon, M., Short, L., Ward, J. (2003). Measuring the impact of attributes that influence consumer attitudes to colorectal cancer screening. ANZ Journal of Surgery, 73, 128Ã¢â¬â132. Szczepura A, Price C, Gumber A (2008) Breast and bowel cancer screening uptake patterns over 15 years for UK south Asian ethnic minority populations, corrected for differences in socio-demographic characteristics. BMC Public Health 8: 346 The NHS Cancer Plan Department of Health, 2000. Towler BP, Irwig L, Glasziou P, Weller D, Kewenter J. Screening for colorectal cancer using the faecal occult blood test, Hemoccult (Cochrane Review). The Cochrane Library, Chichester, UK: John Wiley Sons, Ltd. Issue 3, 2004. Scottish Executive Health Department (2006). Cancer Scenarios: An aid to planning cancer services in Scotland in the next decade. Edinburgh: The Scottish Executive. Steele RJC, Gnauck R, Hrcka R, Kronborg O, Kuntz C, Moayyedi P, et al (2004) Methods and economic considerations, Report from the ESGE/UEGF workshop on colorectal cancer screening. Endoscopy; 36, 349-53. Steele RJC, McClements PL, Libby G et al. (2008) Results from the first three rounds of the Scottish demonstration pilot of FOBT screening for colorectal cancer. Gut 2009 58: 530-535 originally published online November 26, 2008 doi: 10.1136/gut.2008.162883 Tengs TO, Adams ME, Pliskin JS, Safran DG, Siegel JE, Weinstein MC et al (1995) Five hundred life-saving interventions and their cost-effectiveness. Risk Analysis; 15, 369-90. UK CRC Screening Pilot Evaluation Team (2003) Evaluation of UK Colorectal Cancer Screening Pilot Ã¢â¬â Final Report UK Colorectal Cancer Screening Pilot Group (2004) Results of the first cycle of a demonstration pilot of screening for colorectal cancer in the United Kingdom. British Medical Journal, doi:10.1136/bmj.38153.491887.7C ( published 5 July 2004) Von Wagner C, Semmler C, Good A, Wardle J (2009b) Health literacy and self-efficacy for participating in colorectal cancer screening: the role of information processing. Patient Education. 75: 352Ã¢â¬â357 Weller D, Coleman D, Robertson R, Butler P, Melia J, Campbell C, Parker R, Patnick J, Moss S (2007) The UK bowel cancer screening pilot: results of the second round of screening in England. Br J Cancer 97: 1601Ã¢â¬â1605 Weller, D., Alexander, F., Orbell, S. et al. (2003) Evaluation of the UK colorectal cancer screening pilot: final report. NHS Cancer Screening Programmes Worthley, D., Cole, S., Esterman, A., Mehaffey, S., Roosa, N., Smith, A., et al. (2006). Screening for colorectal cancer by faecal occult blood test: Why people choose to refuse. Internal Medicine Journal, 36, 607Ã¢â¬â610. Young GP, St John JB, Winawer SJ, Rozen P. Choice of Faecal Occult Blood Tests for Colorectal cancer Screening: Recommendations Based on Performance Characteristics in population Studies. A WHO (World Health Organisation) and OMED (World Organisation for Digestive Endoscopy) Report. The American Journal of Gastroenterology 2002:97(10) 2499-2507.