***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: Abstract Screening for fecal occult blood by means of guaiac tests has an unsatisfactory sensitivity for the detection of colorectal neoplasms . The immunological determination of human hemoglobin in feces has a higher sensitivity and specificity , but hemoglobin is de grade d during its transport through the gastrointestinal tract . We compared the hemoglobin test to a newly developed immuno-chemiluminometric ( ILMA ) assay for quantifying the hemoglobin-haptoglobin complex in feces which shows high stability against degradation . From each of 621 patients with gastrointestinal complaints before scheduled colonoscopy  we collected two 1-ml sample s from a single stool ; there were no dietary restrictions . The sensitivity for detecting colorectal carcinomas proved 87 % with hemoglobin . With the hemoglobin-haptoglobin complex it was 87 % at a cutoff level of 1.5 µg/g feces , 83 % at 2.0 µg/g feces , and 78 % at 2.5 and 3.0 µg/g feces . The sensitivity for detecting large adenomatous polyps was 54 % with hemoglobin , 76 % with the hemoglobin-haptoglobin complex at a cutoff point of 1.5 µg/g feces , 73 % with the hemoglobin-haptoglobin complex at 2.0 and 2.5 µg/g feces , and 65 % with the hemoglobin-haptoglobin complex at 3.0 µg/g feces . The optimal cutoff point for the hemoglobin-haptoglobin complex was estimated to be 2.0 µg/g stool . The specificity for hemoglobin ( 99 % ) was significantly higher than that for the hemoglobin-haptoglobin complex at 2.0 µg/g feces ( 96 % ) . Immunological determination of the hemoglobin-haptoglobin complex in feces has a comparable sensitivity as the fecal hemoglobin assay for colorectal carcinomas and a significantly higher sensitivity for adenomatous polyps but a significantly lower specificity . Its use for colorectal cancer prevention is currently being evaluated in a screening study This article is one of a series of statements discussing the use of gastrointestinal endoscopy in common clinical situations . The St and ards of Practice Committee of the American Society for Gastrointestinal Endoscopy prepared this text . In preparing this guideline , a MEDLINE literature search was performed , and additional references were obtained from the bibliographies of the identified articles and from recommendations of expert consultants . When little or no data exist from well design ed prospect i ve trials , emphasis is given to results from large series and reports from recognized experts . Guidelines for appropriate use of endoscopy  are based on a critical review of the available data and expert consensus . Further controlled clinical studies are needed to clarify aspects of this statement , and revision may be necessary as new data appear . Clinical consideration may justify a course of action at variance to these recommendations . This guideline replaces and supplements our previous document on colorectal cancer screening and surveillance BACKGROUND Rectal bleeding is common , but it is still unclear which patients require investigation to exclude serious pathology , although it is known that colectoral cancer is very rare under the age of 40 years . Few studies have examined all patients presenting to their primary health physician rather than screening whole population s. AIM The aim of this study was to investigate the view that all patients over the age of 40 who present to their general practitioner with rectal bleeding should undergo investigation by colonoscopy to rule out serious pathology , regardless of symptomatology . METHOD A prospect i ve study was carried out of 99 consecutive patients over 40 years presenting with rectal bleeding to 17 general practice s in Newcastle upon Tyne . RESULTS Serious pathology was detected by colonoscopy in 44.4 % of patients . The diagnoses were : colorectal carcinoma , eight cases ( two Dukes ' grade A , two Dukes ' grade B , four Dukes ' grade C ) ; one or more polyps , 25 cases ( in 17 cases at least one polyp was 5 mm or greater in diameter ) ; inflammatory bowel disease , 11 cases . In the remaining 55 patients , bleeding was associated with diverticular disease ( 16 cases ) and haemorrhoids ( 28 cases ) . No cause was found in 11 patients . This high rate of pathology may be partly caused by selection of cases for referral by the general practitioner , despite efforts to minimize this . Three symptoms as elicited by the colonoscopist were found to be significantly associated with serious disease : blood mixed with stool ( P < 0.001 ) ; change in bowel habit ( P < 0.005 ) ; and the presence of abdominal pain ( P < 0.025 ) . However , symptoms elicited on primary presentation were less helpful and symptoms changed significantly between consultation with the general practitioner and colonoscopy . CONCLUSION All patients over the age of 40 years presenting with rectal bleeding should be referred for flexible sigmoidoscopy or colonoscopy . Symptoms are unhelpful in deciding who requires investigation Hemoccult faecal occult blood testing is widely advocated as a screening test for colorectal cancer but few studies have shown its correlation with conventional methods of investigation for colorectal disease . In a prospect i ve study of 802 symptomatic patients with suspected colorectal disease there was good patient compliance ( 92.5 % ) and a high specificity for colorectal cancer ( 85.4 % ) . The false positive rate was 8.6 % ( 12 of 140 patients with positive results ) , and while the test result was positive in 22 of 26 colonic cancers the false negative rate for rectal cancer ( 45.4 % ) should not detract from its value as a screening test if proper digital anorectal and proctosigmoidoscopic examination are widely practised . A positive Hemoccult test result is a useful indicator for the need to proceed to full colorectal investigation , including colonoscopy A combination guaiac and immunological test Fecatwin/Feca EIA for the detection of faecal occult blood was used in the investigation of 535 symptomatic patients in order to assess the value of this combined test in the detection of colorectal neoplasia . The addition of the immunological part of the test led to an improvement in specificity for colorectal cancer from 80 % to 91 % and an increase in the positive predictive value of the test for colorectal cancer from 14 % to 24 % . However , there was a fall in sensitivity from 75 % to 67 % . There was no substantial advantage in the addition of the immunological part of the test to justify the extra laboratory workload incurred Over a 3‐year period , all patients referred for barium enema examination  had a double‐contrast barium enema and flexible sigmoidoscopy performed on the same day . A total of 462 joint examinations were performed . Abnormalities were found in 193 patients by the use of barium enema , 164 patients by using sigmoidoscopy and 294 by the use of both methods of investigation .  Sigmoidoscopy was superior to barium enema in the detection of polyps and inflammatory bowel disease but barium enema was more sensitive for diverticular disease . The presenting symptoms had no predictive value in distinguishing carcinoma , polyps and diverticular disease . Diverticular disease did not reduce the sensitivity of barium enema examination to polyps in the sigmoid colon . Fibreoptic sigmoidoscopy immediately before barium enema was well tolerated by patients . The investigations were complementary in the diagnosis of colonic polyps , inflammatory bowel disease and diverticular disease Objective . A diagnostic strategy implemented in Denmark in 2002 recommends selective use of colonoscopy in out patients without known colorectal cancer ( CRC ) risk factors who are referred with symptoms consistent with possible CRC . Selection of patients for colonoscopy was based on the presenting symptom(s ) and findings at the initial examination ( flexible sigmoidoscopy/faecal occult blood test ) . The aim of this study was to evaluate the strategy by assessing the prevalence of patients with diagnosed CRC , the frequency of patients with missed CRC , the adherence to the strategy and the number of examinations performed . Material and methods . We prospect ively studied patients aged 40 years and older without known risk factors for CRC , referred to two surgical outpatient clinics during a period of 15–16 months .  Examinations , findings at the examinations , the final diagnoses and date of discharge were recorded . Missed CRCs were identified by follow-up in hospital discharge registries . Results . CRC was diagnosed in 126 ( 5.3 % ; 95 % CI : 4.5–6.3 % ) of the 2361 patients included during the diagnostic work-up . Two additional cancers identified at follow-up were both missed during colonoscopy ( 1.5 % ; 95 % CI : 0.2–5.4 % ) . The adherence to the strategy was 75.7 % , and 125 of the 126 patients with a CRC were examined in conformity with the recommended strategy . Almost 60 % of the patients underwent colonoscopy and almost 50 % underwent both flexible sigmoidoscopy and colonoscopy . Conclusions . The diagnostic strategy is an acceptable alternative to initial colonoscopy , with a low probability of missing a CRC ; however , a considerable proportion of the patients undergo colonoscopy and multiple examinations Although most cases of rectal bleeding are due to local conditions , this symptom is a major sign of colorectal cancer . Little research exists on whether to refer a patient with  rectal bleeding  for further evaluation.1 - 3 We therefore studied the diagnostic value of  rectal bleeding  in relation to a subsequent diagnosis of colorectal cancer . In Belgium , a network of sentinel practice s , covering 1 % of the population , registers epidemiological data .4 The methods used to estimate the denominator ( in patient years ) have been published.4 We analysed data on all patients with colorectal cancer diagnosed in 1993–4 to evaluate sensitivity ( retrospective study ) . We chose  rectal bleeding  as the reason for visiting a general practitioner before colorectal cancer was diagnosed as the main outcome measure . To obtain a positive predictive value ( prospect i ve part of study ) , we included all patients presenting with rectal bleeding in 1993 - 4 . Our reference st and ard was colorectal cancer diagnosed AIM To estimate the prevalence of colorectal cancer ( CRC ) in patients with long lasting colonic symptoms undergoing total colonoscopy ;  and to establish clinical features predicting its occurrence . METHODS This prospect i ve study was carried out in Imam Hospital , Tabriz University of medical sciences , Iran . Continuous patients with long lasting lower gastrointestinal tract symptoms who had the criteria of a colonoscopy were included . The endoscopist visualized the caecum documented by a photo and /or a specimen from terminal ileum . RESULTS Four hundred and eighty consecutive symptomatic patients [ mean age ( SD ) : 42.73 ( 16.21 ) ] were included . The prevalence of colorectal neoplasia  was 15.3 % ( 34 subjects ) and 37.7 % ( 181 subjects ) had a completely normal colon .  Adenomatous polyps were detected in 56 ( 11.7 % ) patients , in 12.3 % of men and 10.9 % of women . The mean age of the patients with a polyp was significantly higher than the others ( 49.53 + /- 14.16 vs 41.85 + /- 16.26 , P = 0.001 ) . Most of the adenomatous polyps were left sided and tubular ; only 22.5 % of polyps were more than 10 mm . Cancer was detected in 16 ( 3.6 % ) of our study population , which was mostly right sided ( 57.2 % ) . The mean age of patients with cancer  was significantly higher than the others ( 60.25 + /- 8.26 vs 42.13 + /- 16.08 , P < 0.005 ) and higher than patients with polyps [ 60.25 ( 8.26 ) vs 49.53 ( 1.91 ) ( P < 0.0005 ) ] . None of the symptoms ( diarrhea , abdominal pain , rectal bleeding , constipation , altering diarrhea and constipation , history of cancer , known irritable bowel disease , history of polyp and fissure or family history of cancer ) were predictors for cancer or polyps , but the age of the patient and unexplained anemia independently predicted cancer . CONCLUSION Less advanced patterns and smaller sizes of adenomas in Iran is compatible with other data from Asia and the Middle East , but in contrast to western countries . Prevalence of colonic neoplasia in our community seems to be lower than that in western population . Colonic symptoms are not predictors for polyps or cancer but unexplained anemia and elder age can predict CRC Objectives : To determine the impact of novel invitation strategies on population participation in faecal immunochemical test (FIT)-based  colorectal cancer ( CRC ) screening . Setting A community screening programme in Adelaide , South Australia . Methods : In total , 2400 people aged 50–74 years were r and omly allocated to one of four CRC screening invitation strategies : ( a ) Control : st and ard invitation-to-screen letter explaining risk of CRC and the concept , value and method of screening ; ( b ) Risk : invitation with additional messages related to CRC risk ; ( c ) Advocacy : invitation with additional messages related to advocacy for screening from previous screening programme 
    Output:
    
None of these six tests was ( sufficiently ) studied in primary care .
Conclusions Although combinations of symptom and results of immunochemical faeces tests showed good diagnostic performance for colorectal cancer , evidence from primary care is lacking .