***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 Screening for colorectal cancer with sigmoidoscopy benefits from the fact that distal findings predict the risk of advanced proximal neoplasms ( APNs ) . This study was aim ed at comparing the existing strategies of postsigmoidoscopy referral to colonoscopy in terms of accuracy and re sources needed . METHODS Asymptomatic individuals aged 50 - 69 years were eligible for a r and omized controlled trial design ed to compare colonoscopy and fecal immunochemical test . Sigmoidoscopy yield was estimated from results obtained in the colonoscopy arm according to three sets of criteria of colonoscopy referral ( from those proposed in the UK Flexible Sigmoidoscopy , Screening for COlon REctum [ SCORE ] , and Norwegian Colorectal Cancer Prevention [ NORCCAP ] trials ) . Advanced neoplasm detection rate , sensitivity , specificity , and number of individuals needed to refer for colonoscopy to detect one APN were calculated . Logistic regression  analysis was performed to identify distal findings associated with APN . All statistical tests were two-sided . RESULTS APN was found in 255 of 5059 ( 5.0 % ) individuals . Fulfillment of UK ( 6.2 % ) , SCORE ( 12.0 % ) , and NORCCAP ( 17.9 % ) criteria varied statistically significantly ( P < .001 ) . The NORCCAP strategy obtained the highest sensitivity for APN detection ( 36.9 % ) , and the UK approach reached the highest specificity ( 94.6 % ) . The number of individuals needed to refer for colonoscopy to detect one APN was 6 ( 95 % confidence interval [ CI ] = 4 to 7 ) , 8 ( 95 % CI = 6 to 9 ) , and 10 ( 95 % CI = 8 to 12 ) when the UK , SCORE , and NORCCAP criteria were used , respectively . The logistic regression analysis identified distal adenoma ≥10 mm ( odds ratio = 3.77 ; 95 % CI = 2.52 to 5.65 ) as the strongest independent predictor of APN . CONCLUSIONS Whereas the NORCCAP criteria achieved the highest sensitivity for APN detection , the UK recommendations benefited from the lowest number of individuals needed to refer for colonoscopy Objective The role of serrated polyps ( SPs ) as colorectal cancer precursor is increasingly recognised . However , the true prevalence SPs is largely unknown . We aim ed to evaluate the detection rate of SPs subtypes as well as serrated polyposis syndrome ( SPS ) among European screening cohorts . Methods Prospect ively collected screening cohorts of ≥1000 individuals were eligible for inclusion .  Colonoscopies performed before 2009 and /or in individuals aged below 50 were excluded  . Rate of SPs was assessed , categorised for histology , location and size . Age – sex – st and ardised number needed to screen ( NNS ) to detect SPs were calculated . Rate of SPS was assessed in cohorts with known colonoscopy follow-up data . Clinical ly relevant SPs ( regarded as a separate entity ) were defined as SPs ≥10 mm and /or SPs > 5 mm in the proximal colon . Results Three faecal occult blood test ( FOBT ) screening cohorts and two primary colonoscopy screening cohorts ( range 1.426–205.949 individuals ) were included . Rate of SPs ranged between 15.1 % and 27.2 % ( median 19.5 % ) , of sessile serrated polyps between 2.2 % and 4.8 % ( median 3.3 % ) and of clinical ly relevant SPs between 2.1 % and 7.8 % ( median 4.6 % ) . Rate of SPs was similar in FOBT-based cohorts as in colonoscopy screening cohorts . No apparent association between the rate of SP and gender or age was shown . Rate of SPS ranged from 0 % to 0.5 % , which increased to 0.4 % to 0.8 % after follow-up colonoscopy . Conclusions The detection rate of SPs is variable among screening cohorts , and st and ards for reporting , detection and histopathological assessment should be established . The median rate , as found in this study , may contribute to define uniform minimum st and ards for males and females between 50 and 75 years of age Summary Background Colorectal cancer is the third most common cancer worldwide . Previous analyses have only reported follow-up after flexible sigmoidoscopy for a maximum of 12 years . We aim ed to examine colorectal cancer incidence and mortality after a single flexible sigmoidoscopy screening and 17 years of follow-up . Methods In this multicentre r and omised trial ( UK Flexible Sigmoidoscopy Screening Trial ) , done between Nov 14 , 1994 , and March 30 , 1999 , 170 432 eligible men and women , who had indicated on a previous question naire that they would probably attend screening if invited , were r and omly assigned ( 1:2 ) to an intervention group ( offered flexible sigmoidoscopy screening ) or a control group ( not contacted ) . R and omisation was done central ly in blocks of 12 , and stratified by trial centre , general practice , and household type . The nature of the intervention did not allow the staff to be masked to arm of the trial ; however , r and omisation was done in batches so that the control group and participants not yet r and omised were unaware of their allocation status . The primary outcomes were incidence and mortality of colorectal cancer . Hazard ratios ( HRs ) and 95 % CIs for colorectal cancer incidence and mortality were estimated for intention-to-treat and per- protocol analyses . The trial is registered with IS RCT N , number 28352761 . Findings Our cohort analysis included 170 034 people : 112 936 in the control group and 57 098 in the intervention group , 40 621 ( 71 % ) of whom were screened and 16 477 ( 29 % ) were not screened . During screening and a median of 17·1 years ' follow-up , colorectal cancer was diagnosed in 1230 individuals in the intervention group and 3253 in the control group , and 353 individuals in the intervention group versus 996 individuals in the control group died from colorectal cancer . In intention-to-treat analyses , colorectal cancer incidence was reduced by 26 % ( HR 0·74 [ 95 % CI 0·70–0·80 ] ; p<0·0001 ) in the intervention group versus the control group and colorectal cancer mortality was reduced by 30 % ( 0·70 [ 0·62–0·79 ] ; p<0·0001 ) in the intervention group versus the control group . In per- protocol analyses , adjusted for non-compliance , colorectal cancer incidence and mortality were 35 % ( HR 0·65 [ 95 % CI 0·59–0·71 ] ) and 41 % ( 0·59 [ 0·49–0·70 ] ) lower in the screened group . Interpretation A single flexible sigmoidoscopy continues to provide substantial protection from colorectal cancer diagnosis and death , with protection lasting at least 17 years . Funding National Institute for Health Research Efficacy and Mechanism Evaluation Context Several immunochemical fecal occult blood tests ( FOBTs ) that use different antibodies against human blood components are available . Contribution This study compared characteristics of 6 qualitative immunochemical FOBTs and 1 guaiac-based FOBT to identify adenomas among adults who attended screening colonoscopy .  The FOBTs had widely varying performance characteristics . Sensitivity and specificity for detecting advanced adenomas ranged from 25 % to 72 % and 70 % to 97 % , respectively , for the immunochemical tests and were 9 % and 96 % , respectively , for the guaiac test . Caution One-day stool sample s were used , and stool was frozen before testing . Implication Qualitative immunochemical FOBTs have varying performance characteristics for detecting precancerous colorectal lesions . The Editors Colorectal cancer ( CRC ) is the third most common cancer in the world ( 1 ) , with about 1 million new cases and more than 500000 deaths per year . Because most cases of CRC are sporadic and develop from removable precancerous lesions ( adenomas ) and curable early- stage cancer ( 2 ) , screening for CRC has high potential for reducing morbidity and mortality . R and omized , controlled trials have demonstrated reduced mortality with guaiac-based fecal occult blood testing ( FOBT ) followed by colonoscopy or sigmoidoscopy if the FOBT result is positive ( 3 ) . However , guaiac-based FOBT , which detects the pseudoperoxidase activity of heme or hemoglobin , has important limitations . It is not specific for human hemoglobin , and false-positive and false-negative results can result from certain compounds or medications in foods ( for example , red meat or vitamin C ) ( 4 ) that should be avoided during the days before testing . Another important limitation is the low diagnostic performance for precursors to CRC . An advantage of guaiac-based FOBT is the simple analysis , which can easily be done at the physician 's office , even though reliable interpretation of test results requires training ( 5 , 6 ) . Immunochemical FOBTs that use specific antibodies against human blood components overcome the problem of diet or medication restriction . Unlike quantitative immunochemical FOBTs , qualitative immunochemical FOBTs that mostly use immunochromatographic technology also allow simple , office-based analysis . However , there are differences among qualitative immunochemical FOBTs . For example , the antibodies used and the different detection limits may influence the diagnostic performance , especially with respect to detection of precursor lesions . We aim ed to determine and compare performance characteristics of different qualitative immunochemical FOBTs for the detection of colorectal adenomas in a large sample of women and men undergoing screening colonoscopy .  Methods Study Design and Sample The analyses were part of the BliTz study ( Begleitende Evaluierung innovativer Testverfahren zur Darmkrebsfrherkennung ) , an ongoing screening study conducted in cooperation with 20 gastroenterology practice s in southwestern Germany since January 2006 that aims to comparatively evaluate new tests for early detection of CRC . The study includes participants undergoing screening colonoscopya procedure that the German health care system has offered since October 2002 to average-risk persons 55 years or older . In Germany , preliminary consultation for any type of cancer screening is mostly done by general practitioners . For screening colonoscopy , patients are referred to the gastroenterologist only when the decision to have colonoscopy is made . All participants had a preliminary consultation with a gastroenterologist to receive detailed information and advice about screening colonoscopy . They were informed about and invited to participate in the study at that time . After we received written informed consent , we asked patients scheduled for screening colonoscopy to provide a stool sample before bowel preparation . Physicians who did colonoscopy and histologic examination were blinded to FOBT results . After colonoscopy , we collected reports on colonoscopic and histologic findings and extracted information in a st and ardized manner while blinded to the results of stool testing . We did not query patients about adverse events of testing ( such as psychological distress ) . The ethics committee of the University of Heidelberg , Heidelberg , Germany , approved the study . We included patients who provided stool sample s for qualitative immunochemical FOBTs until 13 December 2007 . The Figure shows the numbers of all potentially eligible patients . Figure . Study flow diagram . FOBadv = FOB advanced ( ulti med , Ahrensburg , Germany ) ; FOBplus = Bionexia FOBplus ( DIMA , Gttingen , Germany ) ; Hb/Hp C = Bionexia Hb/Hp Complex ( DIMA ) ; HO = HemOccult ( Beckman Coulter , Krefeld , Germany ) ; immoCare = immoCARE-C ( CAREdiagnostica , Voerde , Germany ) ; PreventID CC = PreventID CC ( Preventis , Bensheim , Germany ) ; QuickVue = QuickVue iFOB ( Quidel , San Diego , California ) . * The exclusion of 44 patients overall was due to missing or noninterpretable test cards . Of 1785 patients undergoing screening colonoscopy who agreed to participate , 111 were excluded because of visible rectal bleeding or preceding positive FOBT result . We excluded 13 patients because of inflammatory bowel disease . These patients usually receive close colonoscopic surveillance and would not be regarded as the target population for primary FOBT screening . We excluded 117 patients because they had undergone colonoscopy in the past 5 years and thus would not be eligible for primary FOBT screening  ( if the previous colonoscopy result was positive , they are recommended for colonoscopic surveillance ; if the result was negative , they are at very low risk for colorectal neoplasia ) . We further excluded participants whose stool sample s were collected after colonoscopy only ( and thus violated the study protocol [ n= 65 ] ) , those with inadequate bowel preparation before colonoscopy ( n= 79 ) , and those with incomplete colonoscopy ( that is , the cecum was not reached , [ n= 22 ] ) . We excluded patients who received a histologically confirmed diagnosis of CRC ( this subgroup comprised only 11 participants by the end of 2007 and would not allow meaningfully precise performance estimates for this end point ) . Sensitivity with respect to CRC will be analyzed separately after 
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RESULTS Cross-sectional analysis of endoscopy and pathology data -bases are consistently showing a trend toward an increase with age of the proportion of adenomas located in the proximal colon .
Both endoscopy and FIT are showing a different level of sensitivity for lesions arising in different colonic segments , depending also on screenees characteristics .
Available evidence is supporting the hypothesis of an increase in the proportion of right-sided adenomas with age , while a similar increase has not been reported for SSP/A , at least among subjects aged 50 or older .
The trend toward a proximalization of colorectal adenomas over time , reported by some authors , likely results from improved diagnostic performances and /or the process of population ageing