Erratum

Abstract

An earlier version of the editorial, “Diminutive polyp cancers and the DISCARD strategy: Much ado about nothing or the end of the affair?” by Lai Mun Wang and James E. East (Gastrointest Endosc 2015;82:385-8) was inadvertently published. The correct version is as follows.EditorialThe idea of leaving polyps in situ has been anathema to colonoscopists and patients since endoscopists were first able to safely resect polyps. All lesions were recommended to be resected and sent for pathological evaluation, with surveillance intervals being defined predominantly by the number of adenomatous polyps reported by the pathologist. U.S. guidelines have also emphasized the presence of high-grade dysplasia and villous features as additional pathological risk markers that shorten surveillance intervals1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar; however, this model has been challenged in recent years by an alternative strategy based on new endoscopic technologies such as narrowed spectrum endoscopy (narrow-band imaging, Olympus [Tokyo, Japan]; FICE, Fuji Intelligent Color Enhancement, Fujinon [Tokyo, Japan]; iSCAN, Pentax [Tokyo, Japan]) and confocal laser endomicroscopy, which allow “optical biopsy” of polyps with a high level of accuracy.2Wanders L.K. East J.E. Uitentuis S.E. et al.Diagnostic performance of narrowed spectrum endoscopy, autofluorescence imaging, and confocal laser endomicroscopy for optical diagnosis of colonic polyps: a meta-analysis.Lancet Oncol. 2013; 14: 1337-1347Abstract Full Text Full Text PDF PubMed Scopus (119) Google ScholarThe so-called DISCARD (Detect, InSpect, ChAracterize, Resect, and Discard) strategy represents a paradigm shift in approach to diminutive polyps at colonoscopy whereby the colonoscopist makes a judgment of the likely pathology of the polyp during the procedure, and for adenomatous polyps, resects them but does not send the polyp for pathological examination.3Ignjatovic A. East J.E. Suzuki N. et al.Optical diagnosis of small colorectal polyps at routine colonoscopy (Detect InSpect ChAracterise Resect and Discard; DISCARD trial): a prospective cohort study.Lancet Oncol. 2009; 10: 1171-1178Abstract Full Text Full Text PDF PubMed Scopus (299) Google Scholar Rectosigmoid lesions, if assessed as hyperplastic, may be left in situ. The American Society for Gastrointestinal Endoscopy (ASGE) set standards for the acceptably safe performance of optical biopsy in a Preservation and Incorporation of Valuable Endoscopic Innovations (PIVI) statement in 2011.4Rex D.K. Kahi C. O'Brien M. et al.The American Society for Gastrointestinal Endoscopy PIVI (Preservation and Incorporation of Valuable Endoscopic Innovations) on real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2011; 73: 419-422Abstract Full Text Full Text PDF PubMed Scopus (419) Google Scholar On the basis of available data, both the European Society for Gastrointestinal Endoscopy and the ASGE have now issued guidelines endorsing the use of optical biopsy for “expert” endoscopists in clinical practice as the PIVI criteria appear to be met.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 6Abu Dayyeh B.K. Thosani N. Konda V. et al.ASGE Technology Committee systematic review and meta-analysis assessing the ASGE PIVI thresholds for adopting real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2015; 81: 502-516Abstract Full Text Full Text PDF PubMed Scopus (220) Google ScholarThere is a strong drive to initiate the use of optical biopsy and the associated DISCARD strategy in clinical practice. Pathology can make up to 10% of the cost of a colonoscopy, and 80% of the polyps detected at colonoscopy are diminutive. Therefore, there might be very substantial costs savings for those paying for health care if we abandoned pathology for diminutive polyps, estimated at up to $33 million per year in the United States alone.7Hassan C. Pickhardt P.J. Rex D.K. A resect and discard strategy would improve cost-effectiveness of colorectal cancer screening.Clin Gastroenterol Hepatol. 2010; 8 (869): 865-869Abstract Full Text Full Text PDF PubMed Scopus (201) Google Scholar There are also potential benefits for patients who would be informed of their surveillance interval on the day of the procedure, a “one-stop shop” surveillance experience, rather than waiting for results with attendant anxiety, and avoiding an additional appointment with associated time and administration costs both for clinicians and patients.Nevertheless, there are also risks with adopting the DISCARD strategy for diminutive polyps. Performance among experts appears to meet the PIVI criteria; however, performance among community-based colonoscopists seems less good and insufficient to meet the criteria that the surveillance intervals set with optical biopsy should be ≥90% concordant with those defined by pathology.8Ladabaum U. Fioritto A. Mitani A. et al.Real-time optical biopsy of colon polyps with narrow band imaging in community practice does not yet meet key thresholds for clinical decisions.Gastroenterology. 2013; 144: 81-91Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar We might overuse or underuse surveillance, which might negate cost savings and put patients at risk. Furthermore, not all polyps at colonoscopy are adenomatous or hyperplastic. There is the issue of sessile serrated polyps in the proximal colon, which now contribute to surveillance intervals in guidelines published since the original PIVI statement,1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar as well as juvenile or hamartomatous polyps, which might indicate a familial polyposis syndrome. Diminutive neuroendocrine tumors are not uncommon in the rectum, and without pathology, we would be unable to assess the completeness of resection.Pathological assessment for polyp characterization that is currently essential in determining surveillance intervals is not without its limitation. The issue of pathological accuracy and reproducibility has received some attention as part of the DISCARD story, with reported 10-fold differences in the rate of high-grade dysplasia and villous elements among pathologists looking at the same slide sets, which imply that pathologically defined surveillance intervals might vary significantly. There is also underrecognized awareness that microscopic examination of a polyp is performed routinely at only 3 to 6 hematoxylin and eosin–stained level sections. Additionally, undesirable yet inevitable technical issues of poorly oriented specimens and polypectomy procedure–related crush and cautery tissue artifact are sometimes encountered. Diminutive polyps are often not successfully retrieved, being lost in 13% (402/3060) of diminutive polyps resected at 1 tertiary center.11Komeda Y. Suzuki N. Sarah M. et al.Factors associated with failed polyp retrieval at screening colonoscopy.Gastrointest Endosc. 2013; 77: 395-400Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Therefore, some diminutive polyps and polyp cancers will never reach the pathologist to be assessed. In contrast, optical biopsy is able to make an assessment of all polyps detected in vivo.This leads to the question, “What is the risk of a diminutive polyp cancer?” This is perhaps a 2-part question: what is the risk that there might be cancer in a diminutive polyp and what is the risk of metastatic disease developing after endoscopic resection of a diminutive polyp cancer? The risk of 1 cancer per 3000 diminutive polyps is not formally referenced by Vu et al9Vu H.T. Sayuk G.S. Gupta N. et al.Patient preferences of a resect and discard paradigm.Gastrointest Endosc. 2015; 82: 381-384Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar but is a broadly accepted approximate figure, with Rex et al10Rex D.K. Patel N.J. Vemulapalli K.C. A survey of patient acceptance of resect and discard for diminutive polyps.Gastrointest Endosc. 2015; 82: 376-380Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar citing 13 references to support their less than 1 in 1000 risk; however, this estimate is not evenly distributed across all populations undergoing colonoscopy. The reported incidence of carcinoma in diminutive lesions varies from 0% to 0.6% in 29 case series published from 1979 to 2013.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar In a pooled review of 4 U.S. predominantly screening cohorts of 29,168 patients whose largest polyp was ≤5 mm in size, the cancer rate was 0.04%12Hassan C. Pickhardt P.J. Kim D.H. et al.Systematic review: distribution of advanced neoplasia according to polyp size at screening colonoscopy.Aliment Pharmacol Ther. 2010; 31: 210-217Crossref PubMed Scopus (124) Google Scholar; however, this is in sharp contrast to 2 very large recent European cohorts with respectively more than 100,000 (positive fecal occult blood test result; M. Rutter, personal communication) and 360,000 (screening, surveillance and symptomatic) patients in which the rate of carcinoma in diminutive polyps was 0.1% to 0.4%.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 13Kolligs F.T. Crispin A. Graser A. et al.Risk factors for advanced neoplasia within subcentimetric polyps: implications for diagnostic imaging.Gut. 2013; 62: 863-870Crossref PubMed Scopus (24) Google Scholar This represents up to a 10-fold difference compared with pooled U.S. screening data for diminutive lesions, suggesting that there may be a difference in the rates of carcinoma in diminutive polyps depending on the indication for colonoscopy.Table 1Proportion of diminutive (≤5 mm) adenomas showing submucosal invasion by lesion morphologyAdapted from Oka et al.14Oka S. Tanaka S. Nakadoi K. et al.Endoscopic features and management of diminutive colorectal submucosal invasive carcinoma.Dig Endosc. 2014; 26: 78-83Crossref PubMed Scopus (19) Google ScholarLesion morphologyParis classificationProportion of any sm invasionProportion of sm-deep invasionPolypoidIp, Isp, Is3/6479 (0.05%)1/6479 (0.02%)FlatIIa1/1208 (0.08%)0/1208 (0.0%)DepressedIIc, IIa + IIc11/114 (9.6%)4/114 (3.5%)TotalCombined15/7801 (0.19%)5/7801 (0.06%)sm, Submucosal; sm-deep, invasion ≥1000 μm. Open table in a new tab Will this be enough to convince risk-averse patients and clinicians or will the DISCARD strategy die off due to probability inflation, where even a very small marginal cancer risk seems too large for an individual, leading to the “tragedy of the commons”?15Roman B.R. On marginal health care–probability inflation and the tragedy of the commons.N Engl J Med. 2015; 372: 572-575Crossref PubMed Scopus (2) Google Scholar Even if we were to resect a diminutive polyp cancer and discard it, what is the risk of metastatic disease to the patient? Data are unsurprisingly very limited; however, in the series of Oka et al,14Oka S. Tanaka S. Nakadoi K. et al.Endoscopic features and management of diminutive colorectal submucosal invasive carcinoma.Dig Endosc. 2014; 26: 78-83Crossref PubMed Scopus (19) Google Scholar in 7 diminutive invasive polyp cancers that were operated on, no lymph node metastases were seen.The DISCARD strategy should not be seen by health care payers, pathologists, or patients as a blunt tool to bear down on costs, ignoring risks, but instead as a hair-thin rapier to excise unwarranted cost from our health care systems and at the same time improve patient experience of surveillance colonoscopy. We need comparative effectiveness and outcomes research for the DISCARD strategy versus pathology-based strategies, moving away from diagnostic accuracy and looking at long-term outcomes for patients, if we are to overcome our individual risk aversion.DisclosureDr East has received research funding from Olympus and Cosmo Technologies and is a speaker for Olympus. Dr Wang disclosed no financial relationships relevant to this article. An earlier version of the editorial, “Diminutive polyp cancers and the DISCARD strategy: Much ado about nothing or the end of the affair?” by Lai Mun Wang and James E. East (Gastrointest Endosc 2015;82:385-8) was inadvertently published. The correct version is as follows.EditorialThe idea of leaving polyps in situ has been anathema to colonoscopists and patients since endoscopists were first able to safely resect polyps. All lesions were recommended to be resected and sent for pathological evaluation, with surveillance intervals being defined predominantly by the number of adenomatous polyps reported by the pathologist. U.S. guidelines have also emphasized the presence of high-grade dysplasia and villous features as additional pathological risk markers that shorten surveillance intervals1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar; however, this model has been challenged in recent years by an alternative strategy based on new endoscopic technologies such as narrowed spectrum endoscopy (narrow-band imaging, Olympus [Tokyo, Japan]; FICE, Fuji Intelligent Color Enhancement, Fujinon [Tokyo, Japan]; iSCAN, Pentax [Tokyo, Japan]) and confocal laser endomicroscopy, which allow “optical biopsy” of polyps with a high level of accuracy.2Wanders L.K. East J.E. Uitentuis S.E. et al.Diagnostic performance of narrowed spectrum endoscopy, autofluorescence imaging, and confocal laser endomicroscopy for optical diagnosis of colonic polyps: a meta-analysis.Lancet Oncol. 2013; 14: 1337-1347Abstract Full Text Full Text PDF PubMed Scopus (119) Google ScholarThe so-called DISCARD (Detect, InSpect, ChAracterize, Resect, and Discard) strategy represents a paradigm shift in approach to diminutive polyps at colonoscopy whereby the colonoscopist makes a judgment of the likely pathology of the polyp during the procedure, and for adenomatous polyps, resects them but does not send the polyp for pathological examination.3Ignjatovic A. East J.E. Suzuki N. et al.Optical diagnosis of small colorectal polyps at routine colonoscopy (Detect InSpect ChAracterise Resect and Discard; DISCARD trial): a prospective cohort study.Lancet Oncol. 2009; 10: 1171-1178Abstract Full Text Full Text PDF PubMed Scopus (299) Google Scholar Rectosigmoid lesions, if assessed as hyperplastic, may be left in situ. The American Society for Gastrointestinal Endoscopy (ASGE) set standards for the acceptably safe performance of optical biopsy in a Preservation and Incorporation of Valuable Endoscopic Innovations (PIVI) statement in 2011.4Rex D.K. Kahi C. O'Brien M. et al.The American Society for Gastrointestinal Endoscopy PIVI (Preservation and Incorporation of Valuable Endoscopic Innovations) on real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2011; 73: 419-422Abstract Full Text Full Text PDF PubMed Scopus (419) Google Scholar On the basis of available data, both the European Society for Gastrointestinal Endoscopy and the ASGE have now issued guidelines endorsing the use of optical biopsy for “expert” endoscopists in clinical practice as the PIVI criteria appear to be met.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 6Abu Dayyeh B.K. Thosani N. Konda V. et al.ASGE Technology Committee systematic review and meta-analysis assessing the ASGE PIVI thresholds for adopting real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2015; 81: 502-516Abstract Full Text Full Text PDF PubMed Scopus (220) Google ScholarThere is a strong drive to initiate the use of optical biopsy and the associated DISCARD strategy in clinical practice. Pathology can make up to 10% of the cost of a colonoscopy, and 80% of the polyps detected at colonoscopy are diminutive. Therefore, there might be very substantial costs savings for those paying for health care if we abandoned pathology for diminutive polyps, estimated at up to $33 million per year in the United States alone.7Hassan C. Pickhardt P.J. Rex D.K. A resect and discard strategy would improve cost-effectiveness of colorectal cancer screening.Clin Gastroenterol Hepatol. 2010; 8 (869): 865-869Abstract Full Text Full Text PDF PubMed Scopus (201) Google Scholar There are also potential benefits for patients who would be informed of their surveillance interval on the day of the procedure, a “one-stop shop” surveillance experience, rather than waiting for results with attendant anxiety, and avoiding an additional appointment with associated time and administration costs both for clinicians and patients.Nevertheless, there are also risks with adopting the DISCARD strategy for diminutive polyps. Performance among experts appears to meet the PIVI criteria; however, performance among community-based colonoscopists seems less good and insufficient to meet the criteria that the surveillance intervals set with optical biopsy should be ≥90% concordant with those defined by pathology.8Ladabaum U. Fioritto A. Mitani A. et al.Real-time optical biopsy of colon polyps with narrow band imaging in community practice does not yet meet key thresholds for clinical decisions.Gastroenterology. 2013; 144: 81-91Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar We might overuse or underuse surveillance, which might negate cost savings and put patients at risk. Furthermore, not all polyps at colonoscopy are adenomatous or hyperplastic. There is the issue of sessile serrated polyps in the proximal colon, which now contribute to surveillance intervals in guidelines published since the original PIVI statement,1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar as well as juvenile or hamartomatous polyps, which might indicate a familial polyposis syndrome. Diminutive neuroendocrine tumors are not uncommon in the rectum, and without pathology, we would be unable to assess the completeness of resection.Pathological assessment for polyp characterization that is currently essential in determining surveillance intervals is not without its limitation. The issue of pathological accuracy and reproducibility has received some attention as part of the DISCARD story, with reported 10-fold differences in the rate of high-grade dysplasia and villous elements among pathologists looking at the same slide sets, which imply that pathologically defined surveillance intervals might vary significantly. There is also underrecognized awareness that microscopic examination of a polyp is performed routinely at only 3 to 6 hematoxylin and eosin–stained level sections. Additionally, undesirable yet inevitable technical issues of poorly oriented specimens and polypectomy procedure–related crush and cautery tissue artifact are sometimes encountered. Diminutive polyps are often not successfully retrieved, being lost in 13% (402/3060) of diminutive polyps resected at 1 tertiary center.11Komeda Y. Suzuki N. Sarah M. et al.Factors associated with failed polyp retrieval at screening colonoscopy.Gastrointest Endosc. 2013; 77: 395-400Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Therefore, some diminutive polyps and polyp cancers will never reach the pathologist to be assessed. In contrast, optical biopsy is able to make an assessment of all polyps detected in vivo.This leads to the question, “What is the risk of a diminutive polyp cancer?” This is perhaps a 2-part question: what is the risk that there might be cancer in a diminutive polyp and what is the risk of metastatic disease developing after endoscopic resection of a diminutive polyp cancer? The risk of 1 cancer per 3000 diminutive polyps is not formally referenced by Vu et al9Vu H.T. Sayuk G.S. Gupta N. et al.Patient preferences of a resect and discard paradigm.Gastrointest Endosc. 2015; 82: 381-384Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar but is a broadly accepted approximate figure, with Rex et al10Rex D.K. Patel N.J. Vemulapalli K.C. A survey of patient acceptance of resect and discard for diminutive polyps.Gastrointest Endosc. 2015; 82: 376-380Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar citing 13 references to support their less than 1 in 1000 risk; however, this estimate is not evenly distributed across all populations undergoing colonoscopy. The reported incidence of carcinoma in diminutive lesions varies from 0% to 0.6% in 29 case series published from 1979 to 2013.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar In a pooled review of 4 U.S. predominantly screening cohorts of 29,168 patients whose largest polyp was ≤5 mm in size, the cancer rate was 0.04%12Hassan C. Pickhardt P.J. Kim D.H. et al.Systematic review: distribution of advanced neoplasia according to polyp size at screening colonoscopy.Aliment Pharmacol Ther. 2010; 31: 210-217Crossref PubMed Scopus (124) Google Scholar; however, this is in sharp contrast to 2 very large recent European cohorts with respectively more than 100,000 (positive fecal occult blood test result; M. Rutter, personal communication) and 360,000 (screening, surveillance and symptomatic) patients in which the rate of carcinoma in diminutive polyps was 0.1% to 0.4%.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 13Kolligs F.T. Crispin A. Graser A. et al.Risk factors for advanced neoplasia within subcentimetric polyps: implications for diagnostic imaging.Gut. 2013; 62: 863-870Crossref PubMed Scopus (24) Google Scholar This represents up to a 10-fold difference compared with pooled U.S. screening data for diminutive lesions, suggesting that there may be a difference in the rates of carcinoma in diminutive polyps depending on the indication for colonoscopy.Table 1Proportion of diminutive (≤5 mm) adenomas showing submucosal invasion by lesion morphologyAdapted from Oka et al.14Oka S. Tanaka S. Nakadoi K. et al.Endoscopic features and management of diminutive colorectal submucosal invasive carcinoma.Dig Endosc. 2014; 26: 78-83Crossref PubMed Scopus (19) Google ScholarLesion morphologyParis classificationProportion of any sm invasionProportion of sm-deep invasionPolypoidIp, Isp, Is3/6479 (0.05%)1/6479 (0.02%)FlatIIa1/1208 (0.08%)0/1208 (0.0%)DepressedIIc, IIa + IIc11/114 (9.6%)4/114 (3.5%)TotalCombined15/7801 (0.19%)5/7801 (0.06%)sm, Submucosal; sm-deep, invasion ≥1000 μm. Open table in a new tab Will this be enough to convince risk-averse patients and clinicians or will the DISCARD strategy die off due to probability inflation, where even a very small marginal cancer risk seems too large for an individual, leading to the “tragedy of the commons”?15Roman B.R. On marginal health care–probability inflation and the tragedy of the commons.N Engl J Med. 2015; 372: 572-575Crossref PubMed Scopus (2) Google Scholar Even if we were to resect a diminutive polyp cancer and discard it, what is the risk of metastatic disease to the patient? Data are unsurprisingly very limited; however, in the series of Oka et al,14Oka S. Tanaka S. Nakadoi K. et al.Endoscopic features and management of diminutive colorectal submucosal invasive carcinoma.Dig Endosc. 2014; 26: 78-83Crossref PubMed Scopus (19) Google Scholar in 7 diminutive invasive polyp cancers that were operated on, no lymph node metastases were seen.The DISCARD strategy should not be seen by health care payers, pathologists, or patients as a blunt tool to bear down on costs, ignoring risks, but instead as a hair-thin rapier to excise unwarranted cost from our health care systems and at the same time improve patient experience of surveillance colonoscopy. We need comparative effectiveness and outcomes research for the DISCARD strategy versus pathology-based strategies, moving away from diagnostic accuracy and looking at long-term outcomes for patients, if we are to overcome our individual risk aversion.DisclosureDr East has received research funding from Olympus and Cosmo Technologies and is a speaker for Olympus. Dr Wang disclosed no financial relationships relevant to this article. The idea of leaving polyps in situ has been anathema to colonoscopists and patients since endoscopists were first able to safely resect polyps. All lesions were recommended to be resected and sent for pathological evaluation, with surveillance intervals being defined predominantly by the number of adenomatous polyps reported by the pathologist. U.S. guidelines have also emphasized the presence of high-grade dysplasia and villous features as additional pathological risk markers that shorten surveillance intervals1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar; however, this model has been challenged in recent years by an alternative strategy based on new endoscopic technologies such as narrowed spectrum endoscopy (narrow-band imaging, Olympus [Tokyo, Japan]; FICE, Fuji Intelligent Color Enhancement, Fujinon [Tokyo, Japan]; iSCAN, Pentax [Tokyo, Japan]) and confocal laser endomicroscopy, which allow “optical biopsy” of polyps with a high level of accuracy.2Wanders L.K. East J.E. Uitentuis S.E. et al.Diagnostic performance of narrowed spectrum endoscopy, autofluorescence imaging, and confocal laser endomicroscopy for optical diagnosis of colonic polyps: a meta-analysis.Lancet Oncol. 2013; 14: 1337-1347Abstract Full Text Full Text PDF PubMed Scopus (119) Google ScholarThe so-called DISCARD (Detect, InSpect, ChAracterize, Resect, and Discard) strategy represents a paradigm shift in approach to diminutive polyps at colonoscopy whereby the colonoscopist makes a judgment of the likely pathology of the polyp during the procedure, and for adenomatous polyps, resects them but does not send the polyp for pathological examination.3Ignjatovic A. East J.E. Suzuki N. et al.Optical diagnosis of small colorectal polyps at routine colonoscopy (Detect InSpect ChAracterise Resect and Discard; DISCARD trial): a prospective cohort study.Lancet Oncol. 2009; 10: 1171-1178Abstract Full Text Full Text PDF PubMed Scopus (299) Google Scholar Rectosigmoid lesions, if assessed as hyperplastic, may be left in situ. The American Society for Gastrointestinal Endoscopy (ASGE) set standards for the acceptably safe performance of optical biopsy in a Preservation and Incorporation of Valuable Endoscopic Innovations (PIVI) statement in 2011.4Rex D.K. Kahi C. O'Brien M. et al.The American Society for Gastrointestinal Endoscopy PIVI (Preservation and Incorporation of Valuable Endoscopic Innovations) on real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2011; 73: 419-422Abstract Full Text Full Text PDF PubMed Scopus (419) Google Scholar On the basis of available data, both the European Society for Gastrointestinal Endoscopy and the ASGE have now issued guidelines endorsing the use of optical biopsy for “expert” endoscopists in clinical practice as the PIVI criteria appear to be met.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 6Abu Dayyeh B.K. Thosani N. Konda V. et al.ASGE Technology Committee systematic review and meta-analysis assessing the ASGE PIVI thresholds for adopting real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2015; 81: 502-516Abstract Full Text Full Text PDF PubMed Scopus (220) Google ScholarThere is a strong drive to initiate the use of optical biopsy and the associated DISCARD strategy in clinical practice. Pathology can make up to 10% of the cost of a colonoscopy, and 80% of the polyps detected at colonoscopy are diminutive. Therefore, there might be very substantial costs savings for those paying for health care if we abandoned pathology for diminutive polyps, estimated at up to $33 million per year in the United States alone.7Hassan C. Pickhardt P.J. Rex D.K. A resect and discard strategy would improve cost-effectiveness of colorectal cancer screening.Clin Gastroenterol Hepatol. 2010; 8 (869): 865-869Abstract Full Text Full Text PDF PubMed Scopus (201) Google Scholar There are also potential benefits for patients who would be informed of their surveillance interval on the day of the procedure, a “one-stop shop” surveillance experience, rather than waiting for results with attendant anxiety, and avoiding an additional appointment with associated time and administration costs both for clinicians and patients.Nevertheless, there are also risks with adopting the DISCARD strategy for diminutive polyps. Performance among experts appears to meet the PIVI criteria; however, performance among community-based colonoscopists seems less good and insufficient to meet the criteria that the surveillance intervals set with optical biopsy should be ≥90% concordant with those defined by pathology.8Ladabaum U. Fioritto A. Mitani A. et al.Real-time optical biopsy of colon polyps with narrow band imaging in community practice does not yet meet key thresholds for clinical decisions.Gastroenterology. 2013; 144: 81-91Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar We might overuse or underuse surveillance, which might negate cost savings and put patients at risk. Furthermore, not all polyps at colonoscopy are adenomatous or hyperplastic. There is the issue of sessile serrated polyps in the proximal colon, which now contribute to surveillance intervals in guidelines published since the original PIVI statement,1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar as well as juvenile or hamartomatous polyps, which might indicate a familial polyposis syndrome. Diminutive neuroendocrine tumors are not uncommon in the rectum, and without pathology, we would be unable to assess the completeness of resection.Pathological assessment for polyp characterization that is currently essential in determining surveillance intervals is not without its limitation. The issue of pathological accuracy and reproducibility has received some attention as part of the DISCARD story, with reported 10-fold differences in the rate of high-grade dysplasia and villous elements among pathologists looking at the same slide sets, which imply that pathologically defined surveillance intervals might vary significantly. There is also underrecognized awareness that microscopic examination of a polyp is performed routinely at only 3 to 6 hematoxylin and eosin–stained level sections. Additionally, undesirable yet inevitable technical issues of poorly oriented specimens and polypectomy procedure–related crush and cautery tissue artifact are sometimes encountered. Diminutive polyps are often not successfully retrieved, being lost in 13% (402/3060) of diminutive polyps resected at 1 tertiary center.11Komeda Y. Suzuki N. Sarah M. et al.Factors associated with failed polyp retrieval at screening colonoscopy.Gastrointest Endosc. 2013; 77: 395-400Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Therefore, some diminutive polyps and polyp cancers will never reach the pathologist to be assessed. In contrast, optical biopsy is able to make an assessment of all polyps detected in vivo.This leads to the question, “What is the risk of a diminutive polyp cancer?” This is perhaps a 2-part question: what is the risk that there might be cancer in a diminutive polyp and what is the risk of metastatic disease developing after endoscopic resection of a diminutive polyp cancer? The risk of 1 cancer per 3000 diminutive polyps is not formally referenced by Vu et al9Vu H.T. Sayuk G.S. Gupta N. et al.Patient preferences of a resect and discard paradigm.Gastrointest Endosc. 2015; 82: 381-384Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar but is a broadly accepted approximate figure, with Rex et al10Rex D.K. Patel N.J. Vemulapalli K.C. A survey of patient acceptance of resect and discard for diminutive polyps.Gastrointest Endosc. 2015; 82: 376-380Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar citing 13 references to support their less than 1 in 1000 risk; however, this estimate is not evenly distributed across all populations undergoing colonoscopy. The reported incidence of carcinoma in diminutive lesions varies from 0% to 0.6% in 29 case series published from 1979 to 2013.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar In a pooled review of 4 U.S. predominantly screening cohorts of 29,168 patients whose largest polyp was ≤5 mm in size, the cancer rate was 0.04%12Hassan C. Pickhardt P.J. Kim D.H. et al.Systematic review: distribution of advanced neoplasia according to polyp size at screening colonoscopy.Aliment Pharmacol Ther. 2010; 31: 210-217Crossref PubMed Scopus (124) Google Scholar; however, this is in sharp contrast to 2 very large recent European cohorts with respectively more than 100,000 (positive fecal occult blood test result; M. Rutter, personal communication) and 360,000 (screening, surveillance and symptomatic) patients in which the rate of carcinoma in diminutive polyps was 0.1% to 0.4%.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 13Kolligs F.T. Crispin A. Graser A. et al.Risk factors for advanced neoplasia within subcentimetric polyps: implications for diagnostic imaging.Gut. 2013; 62: 863-870Crossref PubMed Scopus (24) Google Scholar This represents up to a 10-fold difference compared with pooled U.S. screening data for diminutive lesions, suggesting that there may be a difference in the rates of carcinoma in diminutive polyps depending on the indication for colonoscopy.Table 1Proportion of diminutive (≤5 mm) adenomas showing submucosal invasion by lesion morphologyAdapted from Oka et al.14Oka S. Tanaka S. Nakadoi K. et al.Endoscopic features and management of diminutive colorectal submucosal invasive carcinoma.Dig Endosc. 2014; 26: 78-83Crossref PubMed Scopus (19) Google ScholarLesion morphologyParis classificationProportion of any sm invasionProportion of sm-deep invasionPolypoidIp, Isp, Is3/6479 (0.05%)1/6479 (0.02%)FlatIIa1/1208 (0.08%)0/1208 (0.0%)DepressedIIc, IIa + IIc11/114 (9.6%)4/114 (3.5%)TotalCombined15/7801 (0.19%)5/7801 (0.06%)sm, Submucosal; sm-deep, invasion ≥1000 μm. Open table in a new tab Will this be enough to convince risk-averse patients and clinicians or will the DISCARD strategy die off due to probability inflation, where even a very small marginal cancer risk seems too large for an individual, leading to the “tragedy of the commons”?15Roman B.R. On marginal health care–probability inflation and the tragedy of the commons.N Engl J Med. 2015; 372: 572-575Crossref PubMed Scopus (2) Google Scholar Even if we were to resect a diminutive polyp cancer and discard it, what is the risk of metastatic disease to the patient? Data are unsurprisingly very limited; however, in the series of Oka et al,14Oka S. Tanaka S. Nakadoi K. et al.Endoscopic features and management of diminutive colorectal submucosal invasive carcinoma.Dig Endosc. 2014; 26: 78-83Crossref PubMed Scopus (19) Google Scholar in 7 diminutive invasive polyp cancers that were operated on, no lymph node metastases were seen.The DISCARD strategy should not be seen by health care payers, pathologists, or patients as a blunt tool to bear down on costs, ignoring risks, but instead as a hair-thin rapier to excise unwarranted cost from our health care systems and at the same time improve patient experience of surveillance colonoscopy. We need comparative effectiveness and outcomes research for the DISCARD strategy versus pathology-based strategies, moving away from diagnostic accuracy and looking at long-term outcomes for patients, if we are to overcome our individual risk aversion.DisclosureDr East has received research funding from Olympus and Cosmo Technologies and is a speaker for Olympus. Dr Wang disclosed no financial relationships relevant to this article. The idea of leaving polyps in situ has been anathema to colonoscopists and patients since endoscopists were first able to safely resect polyps. All lesions were recommended to be resected and sent for pathological evaluation, with surveillance intervals being defined predominantly by the number of adenomatous polyps reported by the pathologist. U.S. guidelines have also emphasized the presence of high-grade dysplasia and villous features as additional pathological risk markers that shorten surveillance intervals1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar; however, this model has been challenged in recent years by an alternative strategy based on new endoscopic technologies such as narrowed spectrum endoscopy (narrow-band imaging, Olympus [Tokyo, Japan]; FICE, Fuji Intelligent Color Enhancement, Fujinon [Tokyo, Japan]; iSCAN, Pentax [Tokyo, Japan]) and confocal laser endomicroscopy, which allow “optical biopsy” of polyps with a high level of accuracy.2Wanders L.K. East J.E. Uitentuis S.E. et al.Diagnostic performance of narrowed spectrum endoscopy, autofluorescence imaging, and confocal laser endomicroscopy for optical diagnosis of colonic polyps: a meta-analysis.Lancet Oncol. 2013; 14: 1337-1347Abstract Full Text Full Text PDF PubMed Scopus (119) Google Scholar The so-called DISCARD (Detect, InSpect, ChAracterize, Resect, and Discard) strategy represents a paradigm shift in approach to diminutive polyps at colonoscopy whereby the colonoscopist makes a judgment of the likely pathology of the polyp during the procedure, and for adenomatous polyps, resects them but does not send the polyp for pathological examination.3Ignjatovic A. East J.E. Suzuki N. et al.Optical diagnosis of small colorectal polyps at routine colonoscopy (Detect InSpect ChAracterise Resect and Discard; DISCARD trial): a prospective cohort study.Lancet Oncol. 2009; 10: 1171-1178Abstract Full Text Full Text PDF PubMed Scopus (299) Google Scholar Rectosigmoid lesions, if assessed as hyperplastic, may be left in situ. The American Society for Gastrointestinal Endoscopy (ASGE) set standards for the acceptably safe performance of optical biopsy in a Preservation and Incorporation of Valuable Endoscopic Innovations (PIVI) statement in 2011.4Rex D.K. Kahi C. O'Brien M. et al.The American Society for Gastrointestinal Endoscopy PIVI (Preservation and Incorporation of Valuable Endoscopic Innovations) on real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2011; 73: 419-422Abstract Full Text Full Text PDF PubMed Scopus (419) Google Scholar On the basis of available data, both the European Society for Gastrointestinal Endoscopy and the ASGE have now issued guidelines endorsing the use of optical biopsy for “expert” endoscopists in clinical practice as the PIVI criteria appear to be met.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 6Abu Dayyeh B.K. Thosani N. Konda V. et al.ASGE Technology Committee systematic review and meta-analysis assessing the ASGE PIVI thresholds for adopting real-time endoscopic assessment of the histology of diminutive colorectal polyps.Gastrointest Endosc. 2015; 81: 502-516Abstract Full Text Full Text PDF PubMed Scopus (220) Google Scholar There is a strong drive to initiate the use of optical biopsy and the associated DISCARD strategy in clinical practice. Pathology can make up to 10% of the cost of a colonoscopy, and 80% of the polyps detected at colonoscopy are diminutive. Therefore, there might be very substantial costs savings for those paying for health care if we abandoned pathology for diminutive polyps, estimated at up to $33 million per year in the United States alone.7Hassan C. Pickhardt P.J. Rex D.K. A resect and discard strategy would improve cost-effectiveness of colorectal cancer screening.Clin Gastroenterol Hepatol. 2010; 8 (869): 865-869Abstract Full Text Full Text PDF PubMed Scopus (201) Google Scholar There are also potential benefits for patients who would be informed of their surveillance interval on the day of the procedure, a “one-stop shop” surveillance experience, rather than waiting for results with attendant anxiety, and avoiding an additional appointment with associated time and administration costs both for clinicians and patients. Nevertheless, there are also risks with adopting the DISCARD strategy for diminutive polyps. Performance among experts appears to meet the PIVI criteria; however, performance among community-based colonoscopists seems less good and insufficient to meet the criteria that the surveillance intervals set with optical biopsy should be ≥90% concordant with those defined by pathology.8Ladabaum U. Fioritto A. Mitani A. et al.Real-time optical biopsy of colon polyps with narrow band imaging in community practice does not yet meet key thresholds for clinical decisions.Gastroenterology. 2013; 144: 81-91Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar We might overuse or underuse surveillance, which might negate cost savings and put patients at risk. Furthermore, not all polyps at colonoscopy are adenomatous or hyperplastic. There is the issue of sessile serrated polyps in the proximal colon, which now contribute to surveillance intervals in guidelines published since the original PIVI statement,1Lieberman D.A. Rex D.K. Winawer S.J. et al.Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer.Gastroenterology. 2012; 143: 844-857Abstract Full Text Full Text PDF PubMed Scopus (1404) Google Scholar as well as juvenile or hamartomatous polyps, which might indicate a familial polyposis syndrome. Diminutive neuroendocrine tumors are not uncommon in the rectum, and without pathology, we would be unable to assess the completeness of resection. Pathological assessment for polyp characterization that is currently essential in determining surveillance intervals is not without its limitation. The issue of pathological accuracy and reproducibility has received some attention as part of the DISCARD story, with reported 10-fold differences in the rate of high-grade dysplasia and villous elements among pathologists looking at the same slide sets, which imply that pathologically defined surveillance intervals might vary significantly. There is also underrecognized awareness that microscopic examination of a polyp is performed routinely at only 3 to 6 hematoxylin and eosin–stained level sections. Additionally, undesirable yet inevitable technical issues of poorly oriented specimens and polypectomy procedure–related crush and cautery tissue artifact are sometimes encountered. Diminutive polyps are often not successfully retrieved, being lost in 13% (402/3060) of diminutive polyps resected at 1 tertiary center.11Komeda Y. Suzuki N. Sarah M. et al.Factors associated with failed polyp retrieval at screening colonoscopy.Gastrointest Endosc. 2013; 77: 395-400Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Therefore, some diminutive polyps and polyp cancers will never reach the pathologist to be assessed. In contrast, optical biopsy is able to make an assessment of all polyps detected in vivo. This leads to the question, “What is the risk of a diminutive polyp cancer?” This is perhaps a 2-part question: what is the risk that there might be cancer in a diminutive polyp and what is the risk of metastatic disease developing after endoscopic resection of a diminutive polyp cancer? The risk of 1 cancer per 3000 diminutive polyps is not formally referenced by Vu et al9Vu H.T. Sayuk G.S. Gupta N. et al.Patient preferences of a resect and discard paradigm.Gastrointest Endosc. 2015; 82: 381-384Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar but is a broadly accepted approximate figure, with Rex et al10Rex D.K. Patel N.J. Vemulapalli K.C. A survey of patient acceptance of resect and discard for diminutive polyps.Gastrointest Endosc. 2015; 82: 376-380Abstract Full Text Full Text PDF PubMed Scopus (18) Google Scholar citing 13 references to support their less than 1 in 1000 risk; however, this estimate is not evenly distributed across all populations undergoing colonoscopy. The reported incidence of carcinoma in diminutive lesions varies from 0% to 0.6% in 29 case series published from 1979 to 2013.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar In a pooled review of 4 U.S. predominantly screening cohorts of 29,168 patients whose largest polyp was ≤5 mm in size, the cancer rate was 0.04%12Hassan C. Pickhardt P.J. Kim D.H. et al.Systematic review: distribution of advanced neoplasia according to polyp size at screening colonoscopy.Aliment Pharmacol Ther. 2010; 31: 210-217Crossref PubMed Scopus (124) Google Scholar; however, this is in sharp contrast to 2 very large recent European cohorts with respectively more than 100,000 (positive fecal occult blood test result; M. Rutter, personal communication) and 360,000 (screening, surveillance and symptomatic) patients in which the rate of carcinoma in diminutive polyps was 0.1% to 0.4%.5Kaminski M.F. Hassan C. Bisschops R. et al.Advanced imaging for detection and differentiation of colorectal neoplasia: European Society of Gastrointestinal Endoscopy (ESGE) Guideline.Endoscopy. 2014; 46: 435-449Crossref PubMed Scopus (212) Google Scholar, 13Kolligs F.T. Crispin A. Graser A. et al.Risk factors for advanced neoplasia within subcentimetric polyps: implications for diagnostic imaging.Gut. 2013; 62: 863-870Crossref PubMed Scopus (24) Google Scholar This represents up to a 10-fold difference compared with pooled U.S. screening data for diminutive lesions, suggesting that there may be a difference in the rates of carcinoma in diminutive polyps depending on the indication for colonoscopy. sm, Submucosal; sm-deep, invasion ≥1000 μm. Will this be enough to convince risk-averse patients and clinicians or will the DISCARD strategy die off due to probability inflation, where even a very small marginal cancer risk seems too large for an individual, leading to the “tragedy of the commons”?15Roman B.R. On marginal health care–probability inflation and the tragedy of the commons.N Engl J Med. 2015; 372: 572-575Crossref PubMed Scopus (2) Google Scholar Even if we were to resect a diminutive polyp cancer and discard it, what is the risk of metastatic disease to the patient? Data are unsurprisingly very limited; however, in the series of Oka et al,14Oka S. Tanaka S. Nakadoi K. et al.Endoscopic features and management of diminutive colorectal submucosal invasive carcinoma.Dig Endosc. 2014; 26: 78-83Crossref PubMed Scopus (19) Google Scholar in 7 diminutive invasive polyp cancers that were operated on, no lymph node metastases were seen. The DISCARD strategy should not be seen by health care payers, pathologists, or patients as a blunt tool to bear down on costs, ignoring risks, but instead as a hair-thin rapier to excise unwarranted cost from our health care systems and at the same time improve patient experience of surveillance colonoscopy. We need comparative effectiveness and outcomes research for the DISCARD strategy versus pathology-based strategies, moving away from diagnostic accuracy and looking at long-term outcomes for patients, if we are to overcome our individual risk aversion. DisclosureDr East has received research funding from Olympus and Cosmo Technologies and is a speaker for Olympus. Dr Wang disclosed no financial relationships relevant to this article. Dr East has received research funding from Olympus and Cosmo Technologies and is a speaker for Olympus. Dr Wang disclosed no financial relationships relevant to this article. Diminutive polyp cancers and the DISCARD strategy: Much ado about nothing or the end of the affair?Gastrointestinal EndoscopyVol. 82Issue 2PreviewThe idea of leaving polyps in situ has been anathema to colonoscopists and patients since endoscopists were first able to safely resect polyps. All lesions were recommended to be resected and sent for pathological evaluation, with surveillance intervals being defined predominantly by the number of adenomatous polyps reported by the pathologist. U.S. guidelines have also emphasized the presence of high-grade dysplasia and villous features as additional pathological risk markers that shorten surveillance intervals1; however, this model has been challenged in recent years by an alternative strategy based on new endoscopic technologies such as narrowed spectrum endoscopy (narrow-band imaging, Olympus [Tokyo, Japan]; FICE, Fuji Intelligent Color Enhancement, Fujinon [Tokyo, Japan]; iSCAN, Pentax [Tokyo, Japan]) and confocal laser endomicroscopy, which allow “optical biopsy” of polyps with a high level of accuracy. Full-Text PDF