***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Although tests for occult blood in the feces are widely used to screen for colorectal cancers , there is no conclusive evidence that they reduce mortality from this cause . We evaluated a fecal occult-blood test  in a r and omized trial and documented its effectiveness . METHODS We r and omly assigned 46,551 participants 50 to 80 years of age to screening for colorectal cancer once a year , to  screening every two years , or to a control group .  Participants who were screened su bmi tted six guaiac-impregnated paper slides with two smears from each of three consecutive stools . About 83 percent of the slides were rehydrated . Participants who tested positive underwent a diagnostic evaluation that included colonoscopy .  Vital status was ascertained for all study participants during 13 years of follow-up . A committee determined causes of death . A single pathologist determined the stage of each tissue specimen . Differences in mortality from colorectal cancer , the primary study end point , were monitored with the sequential log-rank statistic . RESULTS The 13-year cumulative mortality per 1000 from colorectal cancer was 5.88 in the annually screened group ( 95 percent confidence interval , 4.61 to 7.15 ) , 8.33 in the biennially screened group ( 95 percent confidence interval , 6.82 to 9.84 ) , and 8.83 in the control group ( 95 percent confidence interval , 7.26 to 10.40 ) . The rate in the annually screened group , but not in the biennially screened group , was significantly lower than that in the control group . Reduced mortality in the annually screened group was accompanied by improved survival in those with colorectal cancer and a shift to detection at an earlier stage of cancer . CONCLUSIONS Annual fecal occult-blood testing with rehydration of the sample s decreased the 13-year cumulative mortality from colorectal cancer by 33 percent BACKGROUND Flexible sigmoidoscopy ( FS ) has been recommended as a screening method to reduce mortality from colorectal cancer ( CRC ) . The present study evaluates the effect of adding FS to the fecal occult blood test Hemoccult-II ( H-II ) on diagnostic yield of colorectal neoplasia . METHODS A total of 10,978 normal persons aged 50 - 75 years were invited to participate , 5495 persons being allocated at r and om to H-II and FS and 5483 to H-II alone .  RESULTS In spite of a lower compliance ( 40 % versus 56 % ) for the combined procedure , the diagnostic yield of colorectal neoplasia was higher than for H-II alone ( 12 CRC versus 4 CRC , and 72 large adenomas versus 14 ) . Within 24 - 62 months after screening there were fewer CRCs detected after  H-II + FS than after H-II alone . The stage distribution was less favorable than in screen-detected cases . CONCLUSION One FS may not be an optimal way of screening , but FS deserves to be evaluated in r and omized population studies including repeated H-II tests in the control arm Data are presented on the sensitivity , specificity , and positive predictivity of the Hemoccult test based on the experience of the Minnesota Colon Cancer Control Study , a r and omized clinical trial to determine whether the use of the Hemoccult test can reduce mortality from colorectal cancer . Rehydrating the slides with a drop of water before processing result ed in an increase in positivity ( 2.4 % to 9.8 % ) , and sensitivity ( 80.8 % to 92.2 % ) but a decrease in specificity ( 97.7 % to 90.4 % ) and positive predictivity ( 5.6 % to 2.2 % ) . The effects of age and sex were also evaluated . The test was less specific for men than women ( p = 0.03 ) . Specificity was highest for those less than 60 yr of age and decreased with increasing age ( p = 0.05 ) . The positive predictivity increased with age from 1.6 % for those under 60 yr to 3.6 % for those over 70 yr ( p = 0.0004 ) BACKGROUND Fecal occult-blood testing and sigmoidoscopy have been recommended for screening for colorectal cancer , but the sensitivity of such combined testing for detecting neoplasia is uncertain . At 13 Veterans Affairs medical centers , we performed colonoscopy to determine the prevalence of neoplasia and the sensitivity of one-time screening with a fecal occult-blood test plus sigmoidoscopy . METHODS Asymptomatic subjects ( age range , 50 to 75 years ) provided stool specimens on cards from three consecutive days for fecal occult-blood testing , which were rehydrated for interpretation . They then underwent colonoscopy . Sigmoidoscopy was defined in this study as examination of the rectum and sigmoid colon during colonoscopy , and sensitivity was estimated by determining how many patients with advanced neoplasia had an adenoma in the rectum or sigmoid colon . Advanced colonic neoplasia was defined as an adenoma 10 mm or more in diameter , a villous adenoma , an adenoma with high- grade dysplasia , or invasive cancer . Classification of subjects according to the findings was based on the most advanced lesion . RESULTS A total of 2885 subjects returned the three specimen cards for fecal occult-blood testing and underwent a complete colonoscopic examination . A total of 23.9 percent of subjects with advanced neoplasia had a positive test for fecal occult blood . As compared with subjects who had a negative test for fecal occult blood , the relative risk of advanced neoplasia in subjects who had a positive test was 3.47 ( 95 percent confidence interval , 2.76 to 4.35 ) . Sigmoidoscopy identified 70.3 percent of all subjects with advanced neoplasia . Combined one-time screening with a fecal occult-blood test and sigmoidoscopy identified 75.8 percent of subjects with advanced neoplasia . CONCLUSIONS One-time screening with both a fecal occult-blood test with rehydration and sigmoidoscopy fails to detect advanced colonic neoplasia in 24 percent of subjects with the condition BACKGROUND There is growing evidence that faecal-occult-blood ( FOB ) screening may reduce colorectal cancer ( CRC ) mortality , but this reduction in CRC mortality has not been shown in an unselected population -based r and omised controlled trial . The aim of this study was to assess the effect of FOB screening on CRC mortality in such a setting . METHODS Between February , 1981 , and January , 1991 , 152,850 people aged 45 - 74 years who lived in the Nottingham area of the UK were recruited to our study . Participants were r and omly allocated FOB screening ( 76,466 ) or no screening ( controls ; 76,384 ) . Controls were not told about the study and received no intervention . Screening-group participants were sent a Haemoccult FOB test kit with instructions from their family doctor . FOB tests were not rehydrated and dietary restrictions were imposed only for retesting borderline results . Individuals with negative FOB tests at the first screening , together with those who tested positive but in whom no neoplasia was found on colonoscopy , were invited to take part in further screening every 2 years . Screening was stopped in February , 1995 , by which time screening-group participants had been offered FOB tests between three and six times . Screening-group participants who had a positive test were offered full colonoscopy . All participants were followed up until June , 1995 . The primary outcome measure was CRC mortality . FINDINGS Of the 152,850 individuals recruited to the study , 2599 could not be traced or had emigrated and were excluded from the analysis . Thus , there were 75,253 participants in the screening group and 74,998 controls . 44,838 ( 59.6 % ) screening-group participants completed at least one screening . 28,720 ( 38.2 % ) of these individuals completed all the FOB tests they were offered and 16,118 ( 21.4 % ) completed at least one screening but not all the tests they were offered . 30,415 ( 40.4 % ) did not complete any test . Of 893 cancers ( 20 % stage A ) diagnosed in  screening-group participants ( CRC incidence of 1.49 per 1000 person-years ) , 236 ( 26.4 % ) were detected by FOB screening , 249 ( 27.9 % ) presented after a negative FOB test or investigation , and 400 ( 44.8 % ) presented in non-responders . The incidence of cancer in the control group ( 856 cases , 11 % stage A ) was 1.44 per 1000 person-years . Median follow-up was 7.8 years ( range 4.5 - 14.5 ) . 360 people died from CRC in the screening group compared with 420 in the control group-a 15 % reduction in cumulative CRC mortality in the screening group ( odds ratio=0.85 [ 95 % ; CI 0.74 - 0.98 ] , p = 0.026 ) . INTERPRETATION Our findings together with evidence from other trials suggest that consideration should be given to a national programme of FOB screening to reduce CRC mortality in the general population Colorectal cancer ( CRC ) is a major health concern and a leading cause of cancer death in the Western world . The estimated lifetime risk of CRC is 5 % to 6 % , the incidence rate increases sharply after the age of 50 . Approximately 75 % of new cases occur in individuals at average risk [ 1 , 2 ] . Worldwide , it is estimated that there will be over one million new CRC cases in the year 2001 ( personal communication ) , and the annual ageadjusted incidence rate is 57 per 100 000 . Survival is directly related to the extent of disease at the time of diagnosis . Those diagnosed at an advanced stage have an estimated 5-year survival rate of 7 % , in contrast with a survival rate of 92 % for individuals detected at an early stage , since advanced CRC is largely refractory to conventional therapy and is one of the least curable malignancies [ 3 ] . Despite continuing advances in diagnosis and therapy , long-term survival has not improved significantly over the last four decades , and almost 50 % of CRC patients will eventually die of their disease [ 1 , 2 ] . This situation m and ates improvement in the early detection of this surgically curable disease and preventative interventions to reduce the incidence of the disease and its downstream morbidities and mortality . Indeed , given our underst and ing of the pathogenesis of CRC , current screening technologies , and effective preventative interventions , CRC should be highly preventable . Colorectal cancer has become an important issue for physicians and the general population in the last decade , ever since preventative medicine became a key issue in health care . Indeed , CRC is preventable in up to 90 % of cases [ 4 , 5 ] . CRC fulfils the criteria a disease must have for mass screening . Indeed , intestinal tumorigenesis is exceptionally suited for screening , since the adenoma – carcinoma sequence allows the detection and removal of pre-malignant lesions , and it is well established that patients who are maintained free of adenomas by endoscopic polypectomy are generally kept cancer free [ 4 , 6 , 7 ] . A study using Markov chain analysis has found that CRC decreases the life expectancy calculated for the entire US population by 292 days at age 50–54 years and by 70 days at age 70–74 years [ 8 ] . At the same time , an important controversial issue is the optimal screening approach for the averagerisk population at the age of 50 years . Endoscopic screening is undoubtedly the most effective screening method , but its potential disadvantages , such as invasiveness and cost , should be considered . The simplest and most evaluated screening method available for CRC is the fecal occult blood test ( FOBT ) . This periodic stool testing is considered a lowpriced , non-invasive test that requires no cathartic preparation . It can be performed on mailed specimens without a health center visit , and may reflect the full length of the colon . On the other h and , it is a less sensitive method , since many cancers and the large majority of pre-malignant adenomas do not bleed and are therefore missed . Furthermore , high falsepositive rates , due to dietary peroxidases and meat , or frequent and trivial sources of occult bleeding , lead to unnecessary colonoscopies that drive up programmatic costs . The first national screening program with FOBT was introduced in 1977 in Germany . The evaluation of this program was limited because of confidentiality problems . Case – control studies have yielded conflicting results regarding the effectiveness of FOBT as a screening modality [ 9 ] . The rationale for the use of FOBT screening programs is based on three major long-term r and omized trials . Overall , those trials using annual FOBT have reported a 15 % to 33 % reduction in CRC related death ( for review , see reference 10 ) . The Minnesota prospect i ve case – controlled study [ 11 ] is the study that is most cited . It included 46 000 subjects and showed a reduction in CRC mortality , after 13–18 years of follow-up , of 33 % for annual FOBT examination . Biennial testing result 
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Diagnostic case – control studies generally reported higher sensitivities .
Conclusions Immudia HemSp appeared to be the most accurate immunochemical FOBT , however , there was no clear evidence to suggest whether guaiac or immunochemical FOBTs performed better , either from direct or indirect comparisons .