Efficacy of texture and color enhancement imaging for the visibility and diagnostic accuracy of non-polypoid colorectal lesions.

Objective: A newly launched endoscopy system (EVIS X1, CV-1500; Olympus) is equipped with texture and color enhancement imaging (TXI). We aimed to investigate the efficacy of TXI for the visibility and diagnostic accuracy of non-polypoid colorectal lesions. Methods: We examined 100 non-polypoid lesions in 42 patients from the same position, angle, and distance of the view in three modes: white light imaging (WLI), narrow-band imaging (NBI), and TXI. The primary outcome was to compare polyp visibility in the three modes using subjective polyp visibility score and objective color difference values. The secondary outcome was to compare the diagnostic accuracy without magnification. Results: Overall, the visibility score of TXI was significantly higher than that of WLI (3.7 ± 1.1 vs. 3.6 ± 1.1; p = 0.008) and lower than that of NBI (3.7 ± 1.1 vs. 3.8 ± 1.1; p = 0.013). Color difference values of TXI were higher than those of WLI (11.5 ± 6.9 vs. 9.1 ± 5.4; p < 0.001) and lower than those of NBI (11.5 ± 6.9 vs. 13.1 ± 7.7; p = 0.002). No significant differences in TXI and NBI (visibility score: 3.7 ± 1.0 vs. 3.8 ± 1.1; p = 0.833, color difference values: 11.6 ± 7.1 vs. 12.9 ± 8.3; p = 0.099) were observed for neoplastic lesions. Moreover, the diagnostic accuracy of TXI was significantly higher than that of NBI (65.5% vs. 57.6%, p = 0.012) for neoplastic lesions. Conclusions: TXI demonstrated higher visibility than that of WLI and lower than that of NBI. Further investigations are warranted to validate the performance of the TXI mode comprehensively.

Clinical outcomes and learning curve of Tip-in endoscopic mucosal resection for 15-25 mm colorectal neoplasms among non-experts.

BACKGROUND AND AIM: Tip-in endoscopic mucosal resection (EMR) has a high en bloc resection rate for large colorectal neoplasms. However, non-experts' performance in Tip-in EMR has not been investigated. We investigated whether Tip-in EMR can be achieved effectively and safely even by non-experts. METHODS: This retrospective study included consecutive patients who underwent Tip-in EMR for 15-25 mm colorectal nonpedunculated neoplasms at a Japanese tertiary cancer center between January 2014 and December 2020. Baseline characteristics, treatment outcomes, learning curve of non-experts, and risk factors of failing self-achieved en bloc resection were analyzed. RESULTS: A total of 597 lesions were analyzed (438 by experts and 159 by non-experts). The self-achieved en bloc resection (69.8% vs 88.6%, P < 0.001) and self-achieved R0 resection (58.3% vs 76.5%, P < 0.001) rates were significantly lower in non-experts with <10 cases of experience than in experts, but not in non-experts with >10 cases. Adverse event (P = 0.165) and local recurrence (P = 0.892) rates were not significantly different between experts and non-experts. Risk factors of failing self-achieved en bloc resection were non-polypoid morphology (OR 3.4, 95% CI 1.6-7.3, P = 0.001), lesions with an underlying semilunar fold (OR 3.6, 95% CI 1.6-7.3, P < 0.001), positive non-lifting sign (OR 3.1, 95% CI 1.2-8.0, P = 0.023), and non-experts with an experience of ≤10 cases (OR 3.6, 95% CI 2.1-6.3, P < 0.001). CONCLUSION: The clinical outcomes of Tip-in EMR for 15-25 mm lesions performed by non-experts were favorable.

Gel immersion endoscopic mucosal resection for early gastric neoplasms: a multicenter case series study.

Several cases have been reported that suggest the efficacy of gel immersion endoscopic mucosal resection (GI-EMR) for gastric neoplasms. However, no study has evaluated treatment outcomes of GI-EMR for gastric neoplasms. This study aimed to investigate the efficacy and safety of GI-EMR for early gastric neoplasms. Nine patients (17 lesions) undergoing gastric GI-EMR were included, with a median lesion size of 10 mm (interquartile range [IQR] 5-13 mm). All lesions were protruding or flat elevated. The median procedure time was 3 minutes (IQR 2-5) and en bloc resection was achieved in all cases. Among 15 neoplastic lesions, the R0 resection rate was 86.7% (13/15 lesions). Adverse events included immediate bleeding requiring hemostasis in two cases, which was controlled endoscopically. No delayed bleeding or perforation occurred. In conclusion, GI-EMR may be a safe and effective treatment for early, small gastric neoplasms. However, due to the small sample in the present study, further investigation is required regarding the indication for this technique.

Evaluating false-positive detection in a computer-aided detection system for colonoscopy.

BACKGROUND AND AIM: Computer-aided detection (CADe) systems can efficiently detect polyps during colonoscopy. However, false-positive (FP) activation is a major limitation of CADe. We aimed to compare the rate and causes of FP using CADe before and after an update designed to reduce FP. METHODS: We analyzed CADe-assisted colonoscopy videos recorded between July 2022 and October 2022. The number and causes of FPs and excessive time spent by the endoscopist on FP (ET) were compared pre- and post-update using 1:1 propensity score matching. RESULTS: During the study period, 191 colonoscopy videos (94 and 97 in the pre- and post-update groups, respectively) were recorded. Propensity score matching resulted in 146 videos (73 in each group). The mean number of FPs and median ET per colonoscopy were significantly lower in the post-update group than those in the pre-update group (4.2 ± 3.7 vs 18.1 ± 11.1; P < 0.001 and 0 vs 16 s; P < 0.001, respectively). Mucosal tags, bubbles, and folds had the strongest association with decreased FP post-update (pre-update vs post-update: 4.3 ± 3.6 vs 0.4 ± 0.8, 0.32 ± 0.70 vs 0.04 ± 0.20, and 8.6 ± 6.7 vs 1.6 ± 1.7, respectively). There was no significant decrease in the true positive rate (post-update vs pre-update: 95.0% vs 99.2%; P = 0.09) or the adenoma detection rate (post-update vs pre-update: 52.1% vs 49.3%; P = 0.87). CONCLUSIONS: The updated CADe can reduce FP without impairing polyp detection. A reduction in FP may help relieve the burden on endoscopists.

Evaluating the usefulness of considering the size and morphological type of type B2 vessel area based on Japan Esophageal Society classification in estimating tumor invasion depth in superficial esophageal squamous cell carcinomas: study protocol for a prospective observational study (Japan BEES study).

BACKGROUND: Accurate evaluation of tumor invasion depth is essential to determine the appropriate treatment strategy for patients with superficial esophageal cancer. The pretreatment tumor depth diagnosis currently relies on the magnifying endoscopic classification established by the Japan Esophageal Society (JES). However, the diagnostic accuracy of tumors involving the muscularis mucosa (MM) or those invading the upper third of the submucosal layer (SM1), which correspond to Type B2 vessels in the JES classification, remains insufficient. Previous retrospective studies have reported improved accuracy by considering additional findings, such as the size and macroscopic type of the Type B2 vessel area, in evaluating tumor invasion depth. Therefore, this study aimed to investigate whether incorporating the size and/or macroscopic type of the Type B2 vessel area improves the diagnostic accuracy of preoperative tumor invasion depth prediction based on the JES classification. METHODS: This multicenter prospective observational study will include patients diagnosed with MM/SM1 esophageal squamous cell carcinoma based on the Type B2 vessels of the JES classification. The tumor invasion depth will be evaluated using both the standard JES classification (standard-depth evaluation) and the JES classification with additional findings (hypothetical-depth evaluation) for the same set of patients. Data from both endoscopic depth evaluations will be electronically collected and stored in a cloud-based database before endoscopic resection or esophagectomy. This study's primary endpoint is accuracy, defined as the proportion of cases in which the preoperative depth diagnosis matched the histological depth diagnosis after resection. Outcomes of standard- and hypothetical-depth evaluation will be compared. DISCUSSION: Collecting reliable prospective data on the JES classification, explicitly concerning the B2 vessel category, has the potential to provide valuable insights. Incorporating additional findings into the in-depth evaluation process may guide clinical decision-making and promote evidence-based medicine practices in managing superficial esophageal cancer. TRIAL REGISTRATION: This trial was registered in the Clinical Trials Registry of the University Hospital Medical Information Network (UMIN-CTR) under the identifier UMIN000051145, registered on 23/5/2023.

A novel low-power pure-cut hot snare polypectomy for 10-14 mm colorectal adenomas: An ex vivo and a clinical prospective feasibility study (SHARP trial).

BACKGROUND AND AIM: Hot snare polypectomy using blend or coagulation current is widely used; however, it causes deeper tissue heat injury, leading to adverse events. We hypothesized that hot polypectomy using low-power pure cut current (PureCut, effect 1 10 W) could reduce deeper tissue heat injury. We conducted animal experiments to evaluate the deeper tissue heat injury and conducted a prospective clinical study to examine its cutting ability. METHODS: In a porcine rectum, hot polypectomy using Blend current (EndoCut, effect 3 40 W) and low-power pure cut current was performed. The deepest part of heat destruction and thickness of the non-burned submucosal layer were evaluated histologically. Based on the results, we performed low-power pure cut current hot polypectomy for 10-14 mm adenoma. The primary endpoint was complete resection defined as one-piece resection with negative for adenoma in quadrant biopsies from the defect margin. RESULTS: In experiments, all low-power pure-cut resections were limited within the submucosal layer whereas blend current resections coagulated the muscular layer in 13% (3/23). The remaining submucosal layer was thicker in low-power pure cut current than in blend current resections. In the clinical study, low-power pure-cut hot polypectomy removed all 100 enrolled polyps. For 98 pathologically neoplastic polyps, complete resection was achieved in 84 (85.7%, 95% confidence interval, 77-92%). The lower limit of the 95% confidence interval was not more than 15% below the pre-defined threshold of 86.6%. No severe adverse events occurred. CONCLUSIONS: A novel low-power pure-cut hot polypectomy may be feasible for adenoma measuring 10-14 mm. (UMIN000037678).

A covalent fragment-based strategy targeting a novel cysteine to inhibit activity of mutant EGFR kinase.

Several generations of ATP-competitive anti-cancer drugs that inhibit the activity of the intracellular kinase domain of the epidermal growth factor receptor (EGFR) have been developed over the past twenty years. The first-generation of drugs such as gefitinib bind reversibly and were followed by a second-generation such as dacomitinib that harbor an acrylamide moiety that forms a covalent bond with C797 in the ATP binding pocket. Resistance emerges through mutation of the T790 gatekeeper residue to methionine, which introduces steric hindrance to drug binding and increases the Km for ATP. A third generation of drugs, such as osimertinib were developed which were effective against T790M EGFR in which an acrylamide moiety forms a covalent bond with C797, although resistance has emerged by mutation to S797. A fragment-based screen to identify new starting points for an EGFR inhibitor serendipitously identified a fragment that reacted with C775, a previously unexploited residue in the ATP binding pocket for a covalent inhibitor to target. A number of acrylamide containing fragments were identified that selectively reacted with C775. One of these acrylamides was optimized to a highly selective inhibitor with sub-1 µM activity, that is active against T790M, C797S mutant EGFR independent of ATP concentration, providing a potential new strategy for pan-EGFR mutant inhibition.

A multicenter validation study for determining the condition of nonanatomical or minor anatomical hepatectomies satisfying technical difficulty of current high-level hepatectomy certificated by the Japanese Society of Hepato-Biliary-Pancreatic Surgery.

BACKGROUND: The current high-level hepatectomy (HLH) is certified by the Japanese Society of Hepato-Biliary-Pancreatic Surgery (JSHBPS), comprising only anatomical hepatectomies above Couinaud's segmentectomy. This multicenter study aimed to identify the conditions of non-HLH that satisfy equivalent technical difficulties to HLH. METHODS: Between 2018 and 2021, 595 first open hepatectomies without biliary reconstruction (374 HLHs and 221 non-HLHs) were performed in the five institutions. Non-HLHs belonging to at least one of the three conditions; depth of hepatectomy ≥5 cm, number of resections ≥3 locations and at least one location with a depth of hepatectomy ≥3 cm, and hepatectomy involving the paracaval portion of the caudate lobe was proposed as the candidate for difficult non-HLH. The technical difficulty was estimated by the operative time and blood loss. RESULTS: Difficult non-HLHs were neither associated with shorter operative time (373 min vs. 354 min, p = .184) nor lesser blood loss than those with HLHs (503 mL vs. 436 mL, p = .126). Postoperative complications such as Clavien-Dindo classification grade III or more were not significant between the two groups (18.6% vs. 13.4%, p = 0212). CONCLUSIONS: Difficult non-HLHs were associated with no lesser technical difficulty than those with HLH.

Desmin immunostaining is effective for improving interobserver variability in the depth assessment of the submucosal invasion of colorectal cancers.

Tumor depth evaluation is essential for pathological tumor staging because it affects clinical management as an independent risk factor for lymph node metastasis in colorectal cancers. However, poor interobserver variability of invasion depth has been reported. This study aimed to clarify the effectiveness of desmin immunostaining in the histological diagnosis of colorectal cancer. Overall, 63 sets of slides of colorectal cancer stained with hematoxylin and eosin (H&E) and desmin were prepared and independently reviewed by four examiners. After reviewing the desmin-stained slides, the interobserver variability of H&E slides alone was significantly improved for all examiners. For the assessment of Tis vs. T1, the sensitivity and accuracy were significantly improved for all examiners by combining H&E and desmin immunostaining. For the diagnosis of T1b vs. Tis or T1a, specificity and accuracy were significantly improved by adding desmin immunostaining. Ancillary desmin staining to assess submucosal invasion in colorectal cancers significantly improved interobserver agreement, led to efficient screening of T1 cancers, and reduced excessive T1b diagnoses. The combination of desmin immunostaining and H&E staining is highly recommended for diagnosing invasive colorectal cancer.

Local recurrence risk of esophageal squamous cell carcinoma due to intralesional damage during endoscopic submucosal dissection.

BACKGROUND AND AIM: It is unclear whether additional treatment should be considered given the recurrence risk after endoscopic submucosal dissection (ESD) for esophageal squamous cell carcinoma (ESCC) when the vertical margin is positive or unclear (VM1/VMX) due to intralesional damage. This study aimed to elucidate the local recurrence risk of ESCC caused by intralesional damage during ESD. METHODS: Among consecutive patients with pT1a ESCCs initially treated by ESD at our institution between January 2006 and December 2018, ESCCs diagnosed as VM1/VMX were retrospectively reviewed. Exclusion criteria were piecemeal resection and any additional treatment after ESD. Intralesional damage included the following three types: a macroscopic hole inside the lesion, an incision from the lateral margin of the specimen into the lesion, and crushing injury or burn effect into the deepest area of the lesion without an obvious hole. The local recurrence rate after ESD was primarily analyzed. RESULTS: Of 1174 pT1a ESCCs initially treated using ESD, 22 lesions were histopathologically diagnosed as VM1/VMX due to intralesional damage (1.9%; 95% confidence interval [CI], 1.2-2.8%). At a median follow-up period of 60.0 (interquartile range, 15.0-84.0) months, no local recurrence was observed (0.0%; 95% CI, 0.0-13.3%) among 21 lesions finally evaluated. CONCLUSIONS: The impact of intralesional damage during ESD for ESCC on local recurrence might be negligible. Follow-up without additional treatment may be acceptable even if intralesional damage occurs and results in VM1/VMX after ESD for pT1a ESCCs.

Optimization of endoscopic ultrasound-guided tissue sample acquisition for commercially available comprehensive genome profiling.

BACKGROUND AND AIM: Optimal tumor samples are crucial for successful analysis using commercially available comprehensive genomic profiling (CACGP). However, samples acquired by endoscopic ultrasound-guided tissue acquisition (EUS-TA) are occasionally insufficient, and no consensus on the optimal number of needle passes required for CACGP exists. This study aimed to explore the optimal number of needle passes required for EUS-TA to procure an ideal sample fulfilling the prerequisite criteria of CACGPs. METHODS: Patients who underwent EUS-TA for solid masses between November 2019 and July 2021 were retrospectively studied. The correlation between the acquisition rate of an ideal sample and the number of needle passes mounted on a microscope slide was evaluated. Additionally, the factors predicting a successful analysis were investigated in patients scheduled for CACGP using EUS-TA-obtained samples during the same period. RESULTS: EUS-TAs using 22- and 19-gauge (G) needles were performed in 336 and 57 patients, respectively. There was a positive correlation between the acquisition rate and the number of passes using a 22-G needle (38.9%, 45.0%, 83.7%, and 100% for 1, 2, 3, and 4 passes, respectively), while no correlation was found with a 19-G needle (84.2%, 83.3%, and 85.0% for 1, 2, and 3 passes, respectively). The analysis success rate in patients with scheduled CACGP was significantly higher with ideal samples than with suboptimal samples (94.1% vs 55.0%, P < 0.01). CONCLUSIONS: The optimal estimated number of needle passes was 4 and 1-2 for 22- and 19-G needles, respectively.

A rad50 germline mutation induces tumorigenesis and ataxia-telangiectasia phenotype in a transparent medaka model.

The MRE11A-RAD50-NBS1 complex activates the ataxia-telangiectasia mutated (ATM) pathway and plays a central role in genome homeostasis. The association of RAD50 mutations with disease remains unclear; hence, we adopted a medaka rad50 mutant to demonstrate the significance of RAD50 mutation in pathogenesis using the medaka as an experimental animal. A 2-base pair deletion in the rad50 gene was introduced into transparent STIII medaka using the CRISPR/Cas9 system. The mutant was analyzed histologically for tumorigenicity and hindbrain quality, as well as for swimming behavior, to compare with existing ATM-, MRE11A-, and NBS1-mutation-related pathology. Our results revealed that the medaka rad50 mutation concurrently reproduced tumorigenesis (8 out of 10 rad50Δ2/+ medaka), had a decrease in median survival time (65.7 ± 1.1 weeks in control vs. 54.2 ± 2.6 weeks in rad50Δ2/+ medaka, p = 0.001, Welch's t-test), exhibited semi-lethality in rad50Δ2/Δ2 medaka and most of the major ataxia-telangiectasia phenotypes, including ataxia (rheotaxis ability was lower in rad50Δ2/+ medaka than in the control, Mann-Whitney U test, p < 0.05), and telangiectasia (6 out of 10 rad50Δ2/+ medaka). The fish model may aid in further understanding the tumorigenesis and phenotype of ataxia-telangiectasia-related RAD50 germline mutations and in developing novel therapeutic strategies against RAD50 molecular disorders.

Clinical course and management of adverse events after endoscopic resection of superficial duodenal epithelial tumors: Multicenter retrospective study.

OBJECTIVES: This study aimed to elucidate the clinical course and management of adverse events (AEs) after endoscopic resection (ER) for superficial duodenal epithelial tumors (SDETs). METHODS: Consecutive patients who underwent ER of SDETs between January 2008 and July 2018 at 18 Japanese institutions were retrospectively enrolled. The study outcomes included the clinical course, management, and risk of surgical conversion with perioperative AEs after ER for SDETs. RESULTS: Of the 226 patients with AEs, the surgical conversion rate was 8.0% (18/226), including 3.7% (4/108), 1.0% (1/99), and 50.0% (12/24) of patients with intraoperative perforation, delayed bleeding, or delayed perforation, respectively. In the multivariate logistic analysis, involvement of the major papilla (odds ratio [OR] 12.788; 95% confidence interval [CI] 2.098-77.961, P = 0.006) and delayed perforation (OR 37.054; 95% CI 10.219-134.366, P < 0.001) were significant risk factors for surgical conversion after AEs. Delayed bleeding occurred from postoperative days 1-14 or more, whereas delayed perforation occurred within 3 days in all cases. CONCLUSIONS: The surgical conversion rate was higher for delayed perforation than those for other AEs after ER of SDETs. Involvement of the major papilla and delayed perforation were significant risk factors for surgical conversion following AEs. In addition, reliable prevention of delayed perforation is required for 3 days after duodenal ER to prevent the need for surgical interventions.

Efficacy and Safety of Gel Immersion Endoscopic Mucosal Resection for Non-Pedunculated Colorectal Polyps.

Underwater endoscopic mucosal resection (UEMR) has become a popular endoscopic resection method for large colorectal neoplasms. However, visualization can be poor during UEMR due to the presence of intestinal fluid. Gel immersion endoscopic mucosal resection (GIEMR), using a specially developed gel (Viscoclear®, Otsuka Pharmaceutical Factory, Tokushima, Japan), can improve the visual field. However, reports of GIEMR for colorectal polyps are limited. Herein, we evaluated the short-term outcomes of GIEMR for non-pedunculated colorectal neoplasms (NPCRN). This single-center, retrospective, and observational study includes 25 lesions in 20 patients with NPCRN who underwent GIEMR between January and October 2022. The short-term outcomes and adverse events were evaluated. The lesion locations were as follows: right colon, 18 lesions; left colon, 7 lesions; and rectum, none. The median tumor diameter was 15 (IQR, 10-18) mm. Histological classification was as follows: sessile serrated lesion, 9 cases; adenoma, 12 cases; and intramucosal adenocarcinoma, 4 cases. The overall en bloc resection rates and R0 resection rates were 80% (20/25) and 72% (18/25). For NPCRN in 10-19 mm, the en bloc resection rate was 75% (12/16), with an R0 resection rate of 69% (11/16). No post-polypectomy bleeding, perforation, or post-coagulation syndrome were observed. The findings of our study provide preliminary evidence of the efficacy and safety of GIEMR for NPCRN. Therefore, GIEMR may be a promising novel endoscopic resection method for NPCRN.

Characteristics of synchronous and metachronous duodenal tumors and association with colorectal cancer: a supplementary analysis.

BACKGROUND: We previously reported outcomes of endoscopic resection for duodenal tumors in a large cohort. This study investigated the frequency and characteristics of synchronous and metachronous lesions, and their association with colorectal advanced adenoma (CAA) and colorectal cancer (CRC). METHODS: Patients underwent duodenal endoscopic resection during January 2008 to December 2018. Background and characteristics, incidence of synchronous and metachronous lesions, and incidence of CAA and CRC were investigated. Patients without synchronous lesions were classified as the single group, and those with synchronous lesions as the synchronous group. Patients were also classified as the metachronous and non-metachronous groups. The characteristics among the groups were compared. RESULTS: We included 2658 patients with 2881 duodenal tumors: 2472 (93.0%) patients had single, 186 (7.0%) had synchronous, and 54 (2.0%) had metachronous lesions. The 5-year cumulative incidence of metachronous lesions was 4.1%. In total, 208 (7.8%) had CAA and 127 (4.8%) patients had CRC, and colonoscopy was performed in 936 (35.2%) patients. The incidence of CAA in the synchronous groups tended to be higher compared with that in the single groups (11.8% vs 7.5%, adjusted risk ratio 1.56), and the incidence of CRC in the metachronous groups tended to be higher compared with that in the non-metachronous groups (13.0% vs 4.6%, adjusted risk ratio 2.75), but there was no difference after adjusting for colonoscopy. CONCLUSIONS: This study showed the incidence of synchronous and metachronous duodenal lesions. There was no significant difference in incidence of CAA and CRC among each group, but further studies are warranted.

Endoscopic causes and characteristics of missed gastric cancers after endoscopic submucosal dissection.

BACKGROUND AND AIMS: Because endoscopic submucosal dissection (ESD) for early gastric cancer (EGC) preserves the entire stomach, missed gastric cancers (MGCs) are often found in the remaining gastric mucosa. However, the endoscopic causes of MGCs remain unclear. Therefore, we aimed to elucidate the endoscopic causes and characteristics of MGCs after ESD. METHODS: From January 2009 to December 2018, all patients undergoing ESD for initially detected EGC were enrolled. According to a review of EGD images before ESD, we identified the endoscopic causes (perceptual, exposure, sampling errors, and inadequate preparation) and characteristics of MGC in each endoscopic cause. RESULTS: Of 2208 patients who underwent ESD for initial EGC, 82 patients (3.7%) had 100 MGCs. The breakdown of endoscopic causes of MGCs was as follows: 69 (69%) perceptual errors, 23 (23%) exposure errors, 7 (7%) sampling errors, and 1 (1%) inadequate preparation. Logistic regression analysis showed that the risk factors for perceptual error were male sex (odds ratio [OR], 2.45; 95% confidence interval [CI], 1.16-5.18), isochromatic coloration (OR, 3.17; 95% CI, 1.47-6.84), greater curvature (OR, 2.31; 95% CI, 1.121-4.40), and lesion size ≤12 mm (OR, 1.74; 95% CI, 1.07-2.84). The sites of exposure errors were around the incisura angularis (11 [48%]), posterior wall of the gastric body (6 [26%]), and antrum (5 [21%]). CONCLUSIONS: We identified MGCs in 4 categories and clarified their characteristics. Quality improvements in EGD observation, with attention to the risks of perceptual and site of exposure errors, can potentially prevent missing EGCs.