Doug Altman, medical statistician par excellence: What can radiologists learn from his legacy?

This narrative review describes our experience of working with Doug Altman, the most highly cited medical statistician in the world. Doug was particularly interested in diagnostics, and imaging studies in particular. We describe how his insights helped improve our own radiological research studies and we provide advice for other researchers hoping to improve their own research practice.

Meeting the new joint British Society of Gastrointestinal and Abdominal Radiology and Royal College of Radiologists CT colonography standards: a 6-year experience.

AIM: To audit the performance of computed tomography colonography (CTC) at St Mark's Hospital against the joint British Society of Gastrointestinal and Abdominal Radiology (BSGAR) and Royal College of Radiologists (RCR) standards. MATERIALS AND METHODS: A retrospective audit of all CTC studies between January 2012 to December 2017 was performed against the BSGAR/RCR standards along with additional data outwith the guidelines. Evidence was obtained from a central database, radiology information systems (RISs), picture archiving and communication systems (PACSs), and electronic patient records (EPRs). RESULTS: Over the 6 years, 13,143 CTCs were performed and 12,996 (99%) were adequate or better. Of the cases 1,867 had a >6 mm polyp or cancer reported (polyp identification rate [PIR] 14%) and the positive predictive value (PPV) was 93% (1,148/1,240). Median radiation dose was 458 mGy·cm, mean additional acquisition rate was 19% (2,505/13,143), subsequent endoscopy rate was 9% (1,222/13,143) and mean interpretation time for a negative study was 34.6 minutes. Nine perforations occurred (perforation rate of 0.068%) and one was symptomatic (symptomatic perforation rate of 0.008%). For suspected cancers, the same-day endoscopy rate was 27% (96/360) and same-day staging rate was 76% (272/360). Post-imaging colorectal cancer rates (PICRC) was 3.06 per 100 cancers detected and 0.23 per 1,000 CTCs. The service was always rated "good" or higher by patients. CONCLUSION: This audit shows the CTC service at St Mark's Hospital to be safe and of sufficiently high quality to meet the BSGAR/RCR standards with most outcomes equal to or above the aspirational target. Areas for service and individual reader improvement were also identified.

Transperineal retropubic approach in total pelvic exenteration for advanced and recurrent colorectal and anal cancer involving the penile base: technique and outcomes.

BACKGROUND: Complete pathological resection of locally advanced and recurrent anorectal cancer is considered the most important determinant of survival outcome. Involvement of the retropubic space with cancer threatening or involving the penile base poses specific challenges due to the potential for margin involvement and blood loss from the dorsal venous plexus. In the present study we evaluate a new transperineal surgical approach to excision of anterior compartment organs involved or threatened by cancer which facilitates exposure and visualisation of the bulbar urethra and the deep vein of the penis caudal to the retropubic space and penile base. METHODS: A retrospective study was performed on male patients with tumour extension into the penile base treated at our institution using the transperineal surgical approach. Descriptive data for patient demographics, radiology, operative details, postoperative histology, complications and outcomes were collated. RESULTS: Ten male patients with tumour extension into the penile base were identified. Two patients had recurrent anal cancer, 6 had locally advanced primary rectal cancer and 2 had recurrent rectal cancer. All patients had exenterative surgery with excision of the penile base utilising the transperineal approach. All patients had R0 resection. No local recurrence developed after a median follow up period of 15 months. CONCLUSIONS: The transperineal approach to the penile base and retropubic space allows for high rates of R0 resection margin status with direct visualisation of the dorsal venous plexus, thereby minimising blood loss. In our experience, this technique is the preferred approach to excision of cancers threatening and involving the penile base and also for most male patients requiring total pelvic exenteration.

High subcortical sacrectomy: a novel approach to facilitate complete resection of locally advanced and recurrent rectal cancer with high (S1-S2) sacral extension.

AIM: R0 resection of locally advanced or recurrent rectal cancer is the key determinant of outcome. Disease extension high on the sacrum has been considered a contraindication to surgery because of associated morbidity and difficulty in achieving complete pathological resection. Total sacrectomy has a high morbidity with poor function. METHOD: We describe a novel technique of high subcortical sacrectomy (HiSS) to facilitate complete resection of disease extending to the upper sacrum at S1 and S2 to avoid high or total sacrectomy or a nonoperative approach to management. Details of patient demographics, radiology, operative details, postoperative histology, length of hospital stay and complications were entered into a prospectively maintained electronic patient database. All patients had had preoperative chemoradiotherapy. RESULTS: During 2013-2014, five patients, including three with advanced primary cancer and two with recurrent rectal cancer, underwent excision using this approach. All patients had an R0 resection. Four patients had a minor postoperative complication (Clavien-Dindo Grades I and II) and one had a major complication (Clavien-Dindo Grade IIIb). There was no mortality at 90 days, and four patients were disease free at a median of 18 months. CONCLUSION: Patients with locally advanced and recurrent rectal cancer involving the upper sacrum may be rendered suitable for potentially curative radical resection with a modified approach to sacral resection. This pilot series suggests that this novel technique results in a high rate of complete pathological resection with acceptable morbidity in patients for whom the alternatives would have been an incomplete resection, a total sacrectomy or nonoperative management.

An analysis of the accuracy of computed tomography colonography when defining anatomy for novel full-thickness colonic excision techniques in early colonic neoplasia.

AIM: Full-thickness laparo-endoscopic excision (FLEX) is a new technique developed for the full-thickness excision of colonic adenomas and, potentially, early cancer, avoiding the need for colectomy. FLEX requires accurate preoperative characterization of three key morphological features of the tumour, including its relation to the mesenteric border, its diameter and the circumferential extent of involvement of the bowel wall. This study evaluated the accuracy of CT colonography (CTC) for the assessment of these features in early colonic tumours. METHOD: Consecutive patients undergoing CTC prior to colonic resection for complex benign polyps or UICC Stage 1 cancer were retrospectively analysed by two specialist gastrointestinal radiologists blinded to the subsequent histopathological findings. The location of the tumour in relation to the mesenteric border, its maximum diameter and the circumferential extent of involvement of the colonic wall were correlated with the histopathological examination of the surgical resection specimen. Pearson's correlation coefficient (r) and Kappa agreement (κ) were used to compare the maximum diameter and the circumferential extent of involvement of the colonic wall. RESULTS: Twenty-eight patients with early colonic neoplasia were included. All had had a surgical segmental resection. Four had a benign adenoma and 24 had a TNM Stage 1 cancer. Histopathological assessment of the resected surgical specimen showed that 21 of the 28 lesions were located on the mesenteric border. The median diameter was 35 (interquartile range 28-42) mm; 13 lesions involved less than one-third of the circumference, 11 between one and two-thirds and four more than two-thirds. CTC correctly identified the location of the lesion in relation to the mesenteric border in all 28 cases. Correlation between CTC and histopathology was good for the assessment of the maximum diameter of the lesion (r = 0.81) and the circumferential extent of involvement of the colonic wall (κ = 0.76). CONCLUSION: CTC can accurately assess the key morphological features for the selection of patients with early colonic neoplasia for full-thickness laparo-endoscopic excision.

Implementation of a new CT colonography service: 5 year experience.

AIM: To describe our experience using a 5 year audit of computed tomography colonography (CTC) practice and identify factors that influence diagnostic performance to guide implementation in other centres. MATERIAL AND METHODS: Consecutive patients referred for CTC at a single institution over a 5 year period were identified, and reporting rates and positive predictive value (PPV) calculated for small polyps, large polyps, and colorectal cancer. Diagnostic performance was compared using the Chi-squared test, and trends over time were examined with logistic regression. The effect of faecal tagging and an intravenous spasmolytic were investigated using Fisher's exact test. RESULTS: In total, 4355 CTC examinations were performed. Overall reporting rates and PPV were 17% and 92%, respectively. Negative predictive value (NPV) for cancer was 99.9%. A significant decrease in reporting rate (p < 0.001) was accompanied by an increase in PPV for small polyps (p = 0.02) following the introduction of faecal tagging. Adequacy rates for CTC improved over time (96% to 99%), with improved adequacy rates when using a spasmolytic, 98% versus 96% without. A significant difference in reporting rates, but not PPV, was found between radiologists. CONCLUSION: Accurate colonic investigation using CTC can be delivered safely to a high-risk patient population at a single centre. Faecal tagging and an intravenous spasmolytic improve diagnostic performance.

Extended lateral pelvic sidewall excision (ELSiE): an approach to optimize complete resection rates in locally advanced or recurrent anorectal cancer involving the pelvic sidewall.

BACKGROUND: Complete pathological resection of locally advanced or recurrent rectal and anal cancer is regarded as one of the most important determinants of oncological outcome. Disease in the lateral pelvic sidewall has been considered a contraindication for pelvic exenteration surgery owing to the significant likelihood of incomplete resection. METHODS: We describe a novel technique (ELSiE) to resect disease involving the lateral pelvic sidewall. Patient demographics, post-operative histology, length of hospital stay and complications were collected from prospectively maintained electronic patient database. RESULTS: During 2011-2013, six patients underwent pelvic exenteration surgery with the ELSiE approach. All patients had R0 resection. Three patients required sciatic nerve excision. Four patients developed post-operative complications although no major complications occurred. CONCLUSIONS: Patients with locally advanced and recurrent cancer involving the lateral pelvic sidewall may be rendered suitable for potentially curative radical resection with a modification in the approach to the lateral pelvic sidewall. Our pilot series seems to indicate that our novel technique (ELSiE) is feasible, safe and yields high rates of complete pathological resection.

Requirement for postoperative imaging in an enhanced recovery programme.

AIM: Enhanced recovery after surgery (ERAS) produces benefits to patients by reducing the length of hospital stay and morbidity. Its effect on nursing and physiotherapy workload has been studied, but the demand upon radiology is unclear. We aimed to determine radiology use to understand possible hidden expenditure not included in existing ERAS cost-effectiveness analyses. METHOD: Two-hundred and sixty-five patients from a prospective multidimensional ERAS database were retrospectively assessed for postoperative radiology use. All had undergone colorectal surgery within an established ERAS programme from 2008 to 2009, with all data prospectively recorded. Laparoscopy was offered for all primary colon and rectal resections. All adverse events, including gut dysfunction, surgical site infection and reoperation, were assessed. All radiology within 30 days of surgery was recorded. RESULTS: Radiology data were absent in 12 patients, leaving 253 for analysis. Postoperative radiology was used in 71 (28%) patients, and 41 (16%) had CT of the abdomen and pelvis (A/P) within 30 days of surgery. In 33 (13%) patients this was required during the primary admission, including 30% of patients with any postoperative adverse event. Nine (27%; 3.6% of the whole cohort) of the 33 patients required reoperation. No patient required interventional radiology. The median time to CT (A/P) during primary admission was 5 (interquartile range, 3-8) days. Eight (3%) patients had CT (A/P) after readmission with one reoperation. Forty (16%) patients underwent plain radiology (chest or abdominal) and six (2%) had abdominal ultrasound. Using general estimates of CT and plain radiology total costs, these data suggest an overall radiology cost of over £22,000, amounting to a radiology cost of £90 per ERAS patient. CONCLUSION: Postoperative radiology is required in a significant proportion of ERAS patients, potentially reflecting a low threshold to investigate in the presence of an adverse event. Very few require subsequent intervention. Radiology costs incurred with ERAS should be considered in future economic analyses.

CT colonography in the English Bowel Cancer Screening Programme: national survey of current practice.

AIM: To obtain information regarding the provision of computed tomography colonography (CTC) services to the National Health Service (NHS) Bowel Cancer Screening Programme (BCSP). MATERIALS AND METHODS: Specialist screening practitioners at the 58 BCSP screening centres and lead BCSP radiologists at 110 hospitals performing CTC for the Programme were contacted and completed a semi-structured questionnaire administered by telephone. Responses were collated and descriptive statistics derived. RESULTS: One hundred and seven (98%) SSPs and 103 (94%) radiologists were surveyed. All screening centres had access to CTC at 110 hospital sites. All sites used CTC for failed or contraindicated colonoscopy, 24% used it for patients taking anticoagulants, and 17% for those with fear of colonoscopy. Patient preference was not an indication at any site. Multidetector CT (100%), carbon dioxide insufflators (94%), and CTC software (95%) were almost universal. Ninety-one percent of radiographers and 98% of radiologists were trained in CTC image acquisition and interpretation, respectively. Seventy-five percent of the radiologists were gastrointestinal subspecialists and two-thirds had interpreted more than 300 examinations in clinical practice, although 5% had interpreted fewer than 100. Eighty-one percent of radiologists favoured some form of accreditation for CTC interpretation. CONCLUSIONS: CTC is widely available to the BCSP. Appropriate hardware and software is almost ubiquitous. Most radiographers and radiologists offering CTC to the BCSP have received specific training. Formal service evaluation is patchy. The majority of radiologists would welcome national accreditation for CTC.

CT colonography standards.

Computed tomography (CT) colonography is the established successor to the barium enema for the detection of colonic neoplasia due to superior performance and patient experience. Consequently, CT colonography is widely disseminated across Western populations and increasingly provided by both subspecialist and general radiologists alike. As a result, CT colonography is now part of the core training curriculum for radiology in the UK. However, study data shows wide performance gaps between centres and between individuals of differing experience, which is perhaps unsurprising given the complexity of the CT colonography technique and interpretation. This article summarizes the background, evolution and recommendations of the CT colonography standards document (Appendix) developed by the International CT Colonography Standards Collaboration, which included highly experienced radiologists, radiographers, gastroenterologists, and screening experts. These standards are intended to guide and support radiology teams across the world by promoting methods for improving the quality of CT colonography technique and the patient experience.

CT colonography training for radiographers--a formal evaluation.

AIMS: To evaluate the efficacy of a new intensive "hands-on" course designed to train small teams of radiographers in computed tomography colonography (CTC) technique and initial interpretation for patient triage. MATERIALS AND METHODS: The course comprised small-group lectures, active participation in the daily CTC service with practical technique and image interpretation training by experienced radiologists and radiographers. Evaluation was by assessment of knowledge using randomized sets of multiple choice questions (MCQ; pre/post-course), practical technique using checklists and expert global scores, and interpretation performance outcomes using randomized pre/post-course test datasets (five validated CTC examinations each). Paired t-tests were used to investigate change in performance for MCQ score and interpretation accuracy. RESULTS: Thirteen courses with 49 participants were evaluated over 2 years. Practical skills were high, with mean (SD) checklist scores of 14/15 (0.85) and global scores of 26/30 (2.3). MCQ scores increased significantly from a mean of 59% pre-course to 69% post-course, p<0.001. Correct classification of CTC examination improved significantly from a mean of 55% pre-course to 71% post-course, p<0.001. Cancer and large polyp (>10mm) detection rates also improved significantly from 49% to 60%, p=0.002. CONCLUSION: Structured training in CTC can significantly improve knowledge and interpretation skills of radiographers, while assessing safe procedural performance. Implementation of similar programmes nationally may help reduce performance gaps between centres.

CT colonography: accuracy of initial interpretation by radiographers in routine clinical practice.

AIM: To investigate performance of computed-assisted detection (CAD)-assisted radiographers interpreting computed tomography colonography (CTC) in routine practice. MATERIALS AND METHODS: Three hundred and three consecutive symptomatic patients underwent CTC. Examinations were double-read by trained radiographers using primary two-dimensional/three-dimensional (2D/3D) analysis supplemented by "second reader" CAD. Radiographers recorded colonic neoplasia, interpretation times, and patient management strategy code (S0, inadequate; S1, normal; S2, 6-9 mm polyp; S3, > or = 10 mm polyp; S4, cancer; S5, diverticular stricture) for each examination. Strategies were compared to the reference standard using kappa statistic, interpretation times using paired t-test, learning curves using logistic regression and Pearson's correlation coefficient. RESULTS: Of 303 examinations, 69 (23%) were abnormal. CAD-assisted radiographers detected 17/17 (100%) cancers, 21/28 (72%) polyps > or = 10 mm and 42/60 (70%) 6-9 mm polyps. The overall agreement between radiographers and the reference management strategy was good (kappa 0.72; CI: 0.65, 0.78) with agreement for S1 strategy in 189/211 (90%) exams; S2 in 19/27 (70%); S3 in 12/19 (63%); S4 in 17/17 (100%); S5 in 5/6 (83%). The mean interpretation time was 17 min (SD = 11) compared with 8 min (SD = 3.5) for radiologists. There was no learning curve for recording correct strategies (OR 0.88; p = 0.12) but a significant reduction in interpretation times, mean 14 and 31 min (last/first 50 exams; -0.46; p < 0.001). CONCLUSION: Routine CTC interpretation by radiographers is effective for initial triage of patients with cancer, but independent reporting is currently not recommended.

Flat colon polyps: what should radiologists know?

With the recent publication of international computed tomography (CT) colonography standards, which aim to improve quality of examinations, this review informs radiologists about the significance of flat polyps (adenomas and hyperplastic polyps) in colorectal cancer pathways. We describe flat polyp classification systems and propose how flat polyps should be reported to ensure patient management strategies are based on polyp morphology as well as size. Indeed, consistency when describing flat polyps is of increasing importance given the strengthening links between CT colonography and endoscopy.

Effect of visualization display colour on polyp conspicuity at virtual colonoscopy.

AIM: To investigate the effect of different colour three-dimensional (3D) displays on polyp detection at virtual colonoscopy (VC). METHODS: Five VC trained observers were shown "brief flashes" (lasting 0.2s) of 125 3D endoluminal image snap-shots, repeated for each of six display colours (750 images total). One hundred images contained a single polyp (diameter range 5-42 mm) and 25 contained no polyp ("normal"). Images were reviewed in random order over five reading sessions, readers recording either normality or presence and location of a polyp. Multilevel logistic regression was used to examine any influence of colour on polyp detection stratified according to polyp size (medium 5-9 mm/large >or=10mm). The kappa statistic was used to assess effect of colour on observer agreement. RESULTS: Individual reader polyp detection rates ranged between 75-94%. Compared to the default pink "soft tissue" display, the odds of polyp detection were 0.65 (CI 0.41,1.01) for green, 0.82 (0.53,1.30) for blue, 1 (0.63,1.59) for red, 1.12 (0.7,1.79) for monochrome, and 1.15 for yellow (0.72,1.84). Overall, there was no significant difference between the displays (p=0.11). Including normal cases, there was no overall difference in correct case classification between the six colours (p=0.44). The odds of detecting large versus medium polyps was significantly greater for 3/5 observers; odds ratio (OR) 2.84-10.1, although unaffected by display colour (p=0.3). CONCLUSION: The background colour display generally has a minimal effect on polyp detection at VC, although green should be avoided.

CT enterography: review of technique and practical tips.

CT enterography is a new non-invasive imaging technique that offers superior small bowel visualisation compared with standard abdomino-pelvic CT, and provides complementary diagnostic information to capsule endoscopy and MRI enterography. CT enterography is well tolerated by patients and enables accurate, efficient assessment of pathology arising from the small bowel wall or surrounding organs. This article reviews the clinical role of CT enterography, and offers practical tips for optimising technique and accurate interpretation.

Imaging assessment of desmoid tumours in familial adenomatous polyposis: is state-of-the-art 1.5 T MRI better than 64-MDCT?

OBJECTIVE: Desmoid tumour is a common extraintestinal manifestation of patients with familial adenomatous polyposis (FAP) who have undergone prophylactic colectomy. We aimed to determine whether MRI provides equivalent or better assessment of desmoid tumours than CT, the current first-line investigation. METHODS: Following ethics approval and informed consent, FAP patients with known desmoid tumour underwent contrast-enhanced 64-slice multidetector CT (MDCT) and 1.5 T MRI (incorporating T(1) weighted, T(2) weighted, short tau inversion-recovery and T(1) weighted with contrast, axial, sagittal and coronal sequences). The number, site, size, local extent, tumour signal intensity and desmoid-to-aorta enhancement ratio were analysed. RESULTS: MRI identified 23 desmoid tumours in 9 patients: 9 intra-abdominal desmoid (IAD) tumours, 10 abdominal wall desmoid (AWD) tumours and 4 extra-abdominal desmoid (EAD) tumours. CT identified only 21 desmoids; 1 EAD and 1 AWD were not identified. The two modalities were equivalent in terms of defining local extent of desmoid. Five IAD tumours involved the bowel, six caused ureteric compression and none compromised the proximal superior mesenteric artery. There was no difference in median desmoid size: 56.7 cm(2) (range 2-215 cm(2)) on MDCT and 56.3 cm(2) (3-215 cm(2)) on MRI (p=0.985). The mean MRI enhancement ratio, at 1.12 (standard deviation 0.43), was greater than the CT enhancement ratio, which was 0.48 (0.16) (p<0.0001). High signal intensity on T(2) MRI was associated with increased MRI enhancement ratio (p=0.006). CONCLUSIONS: MRI is at least equivalent (and may be superior) to MDCT for the detection of desmoid tumours in FAP. Coupled with the advantage of avoiding radiation, it should be considered as the primary imaging modality for young FAP patients.

Review article: medical, surgical and radiological management of perianal Crohn's fistulas.

BACKGROUND: Crohn's anal fistulas are common and cause considerable morbidity. Their management is often difficult; medical and surgical treatments rarely lead to true healing with frequent recurrence and complications. AIM: To examine medical treatments previously and currently used, surgical techniques and the important role of optimal imaging. METHODS: We conducted a literature search in the Pub Med database using Crohn's, Anal Fistula, Surgery, Imaging and Medical Treatment as search terms. RESULTS: Antibiotics and immunosuppressants have a role, but slow initial response, side effects and relatively low remission rates of up to around a third with frequent recurrence limit their value. Long-term infliximab produces clinical remission in 36-58% of patients with combined medical and surgical management achieving optimal outcomes. Traditional and newer surgical procedures often have a high rate of recurrence with a significant risk of temporary or, in up to 10% of cases, permanent stomas, incontinence and unhealed or slowly healing wounds in 30%. CONCLUSIONS: Management of Crohn's anal fistulas remains challenging. Established principles are to drain infection, use setons as required, aggressively manage active proctitis, give antibiotics, immunosuppressants and employ anti-TNFα therapy, and they demand significant co-operation between gastroenterologists and surgeons.

Prospective assessment of the effect on quality of life of anti-tumour necrosis factor therapy for perineal Crohn's fistulas.

BACKGROUND: Anti-tumour necrosis factor (TNF) therapy effectively treats Crohn's perineal fistulas (CPF); the effect on health-related quality of life (HRQoL) remains unknown. AIMS: To evaluate the effect of anti-TNF therapy on the HRQoL of patients with CPF in daily clinical practice. METHODS: Prospective evaluation of clinical and magnetic resonance imaging (MRI) responses, disease activity (Perianal Disease Activity Index - PDAI), and HRQoL assessment [Inflammatory Bowel Disease Questionnaire (IBDQ)] in patients receiving anti-TNF therapy for CPF treated up to 12 months. RESULTS: In all, 26 patients with CPF were treated (mean age 39 years; 19 infliximab, 7 adalimumab). At baseline, 85% patients had impaired IBDQ scores (mean 137; 'normal' >170). At 12 months, mean increases in IBDQ score for infliximab and adalimumab treated patients were 40 and 41 points respectively (P < 0.05). There were significant improvements in all IBDQ subscores (bowel, emotional, systemic, social) at 12 months (all P < or = 0.003). Fourteen patients (74%) on infliximab and six on adalimumab (86%) achieved IBDQ score > or =170. Mean increase in IBDQ score was 50, 34 and 16 points in patients with clinical fistula closure (P < 0.001), clinical response (P = 0.002) and no response (n = 1) respectively. IBDQ score increased for patients with MRI healing (P < 0.001) and MRI improvement (P = 0.016), but not for those with no MRI change (n = 2). IBDQ correlated significantly with PDAI at baseline and at 12 months. CONCLUSION: Anti-TNF therapy improves HRQoL in patients with CPF at 12 months and this improvement is most pronounced in patients with clinical and MRI healing.

Computer-aided detection for CT colonography: incremental benefit of observer training.

The purpose of this study was to investigate the incremental effect of focused training on observer performance when using computer-assisted detection (CAD) software to interpret CT colonography (CTC). Six radiologists who were relatively inexperienced with CTC interpretation underwent 1 day of focused training before reading 20 patient datasets with the assistance of CAD software (ColonCAR 1.3, Medicsight PLC). Sensitivity, specificity and interpretation times were determined and compared with previous performance when reading the same datasets but without the benefit of focused training, using the binomial exact test and Wilcoxon's signed rank test. Per-polyp sensitivity improved after training by 18% overall (95% confidence interval (CI): 14-24%, p<0.001) and was greatest for polyps of 6-9 mm (26%, 95% CI: 18-34%, p<0.001). Absolute sensitivity was 23% (9-36%), 51% (33-71%) and 74% (44-100%) for polyps of or=10 mm, respectively. Specificity fell significantly after focused training (median of 5.5 false positives per 20 datasets (interquartile range (IQR): 4-6) post-training vs median of 2.5 (IQR: 1-5) pre-training, p = 0.03). Interpretation time also increased significantly after training (from a median of 9.3 min (IQR: 9.3-14.5 min) to a median of 17.1 min (IQR: 15.4-19.4 min), p = 0.03). In conclusion, one day of training increases observer polyp sensitivity when using CAD for CTC at the expense of increased reporting time and reduction in specificity.