Faecal calprotectin is a surrogate marker of biliary inflammation in primary sclerosing cholangitis associated inflammatory bowel disease.

Objective: Faecal calprotectin (fCAL) is an established marker of intestinal inflammation in inflammatory bowel disease (IBD). Disproportionally high fCAL levels, for the severity of intestinal inflammation, have been previously observed in primary sclerosing cholangitis associated IBD (PSC-IBD). The aim of this study was to test the hypothesis that fCAL is a marker of biliary injury in PSC-IBD. Methods: We used two cohorts: (1) post hoc analysis of a colonoscopic surveillance study allowing correlation of fCAL to endoscopic severity as measured by the ulcerative colitis endoscopic index of severity (UCEIS) in PSC-IBD (n=20) and ulcerative colitis (UC, n=20) and (2) prospective recruitment of patients attending for endoscopic retrograde cholangiopancreatography allowed the correlation of fCAL to biliary calprotectin (n=8). Results: A strong correlation was seen between fCAL and UCEIS in UC (r=0.821, 95% CI (0.585 to 0.929), p<0.0001). In PSC-IBD, the correlation was weaker (r=0.596, 95% CI (0.195 to 0.8260), p=0.006). PSC-IBD patients with endoscopically quiescent colitis (UCEIS: 0-1) had higher fCAL than patients with UC (279 µg/g, IQR (68-601) vs 30 µg/g, IQR (14-107), p=0.015). This was associated with higher risk of biliary complications like need for antibiotics or instrumentation (HR 16.39, 95% CI (2.98 to 90.25)) rather than colitis flares (follow-up: 12 months). Calprotectin measured in faeces correlated positively with biliary calprotectin (r=0.898, p=0.0024). Conclusion: fCAL is a surrogate marker for biliary inflammation in PSC-IBD. Trial registration number: NCT02543021.

Comparative effectiveness of a second-line biologic in patients with ulcerative colitis: vedolizumab followed by an anti-TNF versus anti-TNF followed by vedolizumab.

Background: Sequential drug treatment with biological agents in ulcerative colitis (UC) is becoming increasingly complex. There are few studies comparing head-to-head outcomes in second-line treatments. The study assesses whether using anti-tumour necrosis factor (anti-TNF)-α therapy following the α4ß7 integrin blocker vedolizumab (VDZ) or VDZ after an anti-TNF has more favourable clinical outcomes in UC in a real-world outpatient setting. Methods: Patients with UC who were exposed to first-line anti-TNF (adalimumab or infliximab) or VDZ who subsequently switched to the alternate class between May 2013 and August 2020 were identified by reviewing patient databases at 10 hospitals. Data were collected retrospectively using patient records. Baseline demographics, disease activity indices, biochemical markers, endoscopic Mayo score, colectomy rates, treatment persistence and urgent hospital utilisation composite endpoint (UHUC) rates were examined over a 52-week period. Results: Second-line week 52 treatment persistence was higher in the VDZ group (71/81, 89%) versus the anti-TNF group (15/34, 44%; p=0.0001), as were week 52 colectomy-free survival (VDZ: 77/80, 96%, vs anti-TNF: 26/32, 81%; p=0.009), week 52 UHUC survival (VDZ: 68/84, 81%, vs anti-TNF: 20/34, 59%; p=0.002) and week 52 corticosteroid-free clinical remission (CFCR) rates (VDZ: 22/34, 65%, vs anti-TNF: 4/20, 20%; p=0.001). Conclusion: Compared with second-line anti TNF usage, the VDZ second-line cohort had significantly higher 52-week treatment persistence, UHUC survival, higher colectomy-free survival rates and higher week 52 CFCR. These data suggest that VDZ is an effective biologic in UC as a second-line therapy after anti-TNF exposure. It highlights the effect of biological order on clinically important outcomes.

Clinical course of inflammatory bowel disease and impact on liver disease outcomes in patients with autoimmune sclerosing cholangitis.

BACKGROUND & AIMS: Autoimmune sclerosing cholangitis (ASC) is a childhood sclerosing cholangitis frequently associated with inflammatory bowel disease (IBD). We describe the IBD phenotype in ASC patients and associated liver disease outcomes. METHODS: Single center retrospective observational review of ASC patients, with a control population of pediatric IBD. Demographic and clinical parameters were obtained. Clinical endpoints were escalation of IBD therapy (biologic or colectomy) and transplant-free survival. RESULTS: In 93 ASC patients (53.8% female) and median follow up of 172 months: 70% had IBD, 25.8% underwent liver transplant. Median age at liver transplant was 21.7 years, at 131 months from ASC diagnosis. There was no association between presence of IBD and transplant-free survival, whilst those requiring second-line immunomodulators for ASC had poorer long-term liver prognosis. During follow-up 22 (33.8%) ASC-IBD required biologic or colectomy. On multivariate analysis ASC was associated with a lower risk of escalation of IBD therapy (HR 0.14, 95% CI 0.05-0.42; P=.001), including biologic therapy (HR 0.21, 95% CI 0.08-0.55, P=.002), but not colectomy on univariate analysis (HR 1.54, 95% CI 0.43-5.44, P=.51). CONCLUSIONS: IBD is common in ASC and during longterm follow up a third of ASC-IBD required escalation of IBD therapy; however ASC-IBD was lower risk compared to IBD alone. IBD does not appear to impact on transplant-free survival in patients with ASC, however second-line immunomodulators for ASC are associated with poorer IBD and liver outcomes.

Mechanical and hydrodynamic analyses of helical strake-like ridges in a glass sponge.

From the discovery of functionally graded laminated composites, to near-structurally optimized diagonally reinforced square lattice structures, the skeletal system of the predominantly deep-sea sponge Euplectella aspergillum has continued to inspire biologists, materials scientists and mechanical engineers. Building on these previous efforts, in the present study, we develop an integrated finite element and fluid dynamics approach for investigating structure-function relationships in the complex maze-like organization of helical ridges that surround the main skeletal tube of this species. From these investigations, we discover that not only do these ridges provide additional mechanical reinforcement, but perhaps more significantly, provide a critical hydrodynamic benefit by effectively suppressing von Kármán vortex shedding and reducing lift forcing fluctuations over a wide range of biologically relevant flow regimes. By comparing the disordered sponge ridge geometry to other more symmetrical strake-based vortex suppression systems commonly employed in infrastructure applications ranging from antennas to underwater gas and oil pipelines, we find that the unique maze-like ridge organization of E. aspergillum can completely suppress vortex shedding rather than delaying their shedding to a more downstream location, thus highlighting their potential benefit in these engineering contexts.

Near-focus narrow-band imaging classification of villous atrophy in suspected celiac disease: development and international validation.

BACKGROUND AND AIMS: There are no agreed-on endoscopic signs for the diagnosis of villous atrophy (VA) in celiac disease (CD), necessitating biopsy sampling for diagnosis. Here we evaluated the role of near-focus narrow-band imaging (NF-NBI) for the assessment of villous architecture in suspected CD with the development and further validation of a novel NF-NBI classification. METHODS: Patients with a clinical indication for duodenal biopsy sampling were prospectively recruited. Six paired NF white-light endoscopy (NF-WLE) and NF-NBI images with matched duodenal biopsy sampling including the bulb were obtained from each patient. Histopathology grading used the Marsh-Oberhuber classification. A modified Delphi process was performed on 498 images and video recordings by 3 endoscopists to define NF-NBI classifiers, resulting in a 3-descriptor classification: villous shape, vascularity, and crypt phenotype. Thirteen blinded endoscopists (5 expert, 8 nonexpert) then undertook a short training module on the proposed classification and evaluated paired NF-WLE-NF-NBI images. RESULTS: One hundred consecutive patients were enrolled (97 completed the study; 66 women; mean age, 51.2 ± 17.3 years). Thirteen endoscopists evaluated 50 paired NF-WLE and NF-NBI images each (24 biopsy-proven VAs). Interobserver agreement among all validators for the diagnosis of villous morphology using the NF-NBI classification was substantial (κ = .71) and moderate (κ = .46) with NF-WLE. Substantial agreement was observed between all 3 NF-NBI classification descriptors and histology (weighted κ = 0.72-.75) compared with NF-WLE to histology (κ = .34). A higher degree of confidence using NF-NBI was observed when assessing the duodenal bulb. CONCLUSIONS: We developed and validated a novel NF-NBI classification to reliably diagnose VA in suspected CD. There was utility for expert and nonexpert endoscopists alike, using readily available equipment and requiring minimal training. (Clinical trial registration number: NCT04349904.).

Nutrient, Fibre, and FODMAP Intakes and Food-related Quality of Life in Patients with Inflammatory Bowel Disease, and Their Relationship with Gastrointestinal Symptoms of Differing Aetiologies.

BACKGROUND AND AIMS: Certain foods are reported as gut symptom triggers in inflammatory bowel disease [IBD], and fructans are shown to worsen non-inflammatory symptoms in inactive IBD, which may result in self-imposed dietary restrictions. The aim of this study was to investigate nutrient and FODMAP intakes, and the relationship between gut symptoms and dietary intake, in IBD. METHODS: Nutrient, fibre, and FODMAP intakes were estimated using 7-day food records in patients with active IBD [Active IBD], inactive IBD with non-inflammatory gut symptoms [Inactive IBD-GI], inactive IBD without gut symptoms [Inactive IBD], and healthy controls. Nutrient intakes, numbers of participants achieving national recommendations, and food-related quality of life [FR-QoL] were compared across study groups. RESULTS: Food diaries were obtained from 232 patients with IBD [65 Active IBD, 86 Inactive IBD-GI, 81 Inactive IBD] and 84 healthy controls. Patients with Active IBD had significantly lower intakes of numerous micronutrients, including iron, folate, and vitamin C, compared with controls. All IBD groups consumed less total fibre [4.5 to 5.8 g/day] than controls [p = 0.001], and total FODMAP and fructan intakes were lower in Active IBD compared with controls. Strikingly, FR-QoL was significantly lower in all IBD groups compared with controls [all p = 0.001]. CONCLUSIONS: This study revealed lower intakes of fibre, FODMAPs, and micronutrients, in addition to poorer FR-QoL, in Active IBD and Inactive IBD-GI with gut symptoms compared with healthy controls. Future research should address dietary restrictions responsible for these differences.

Predictors of adherence to a gluten-free diet in celiac disease: Do knowledge, attitudes, experiences, symptoms, and quality of life play a role?

OBJECTIVES: This study aimed to identify the relationship between adherence to a gluten-free diet (GFD) and demographic characteristics, knowledge, attitudes, and beliefs regarding celiac disease (CD) and GFD, experiences of following a GFD, symptoms, and quality of life (QoL). METHODS: Patients with CD were recruited from outpatient clinics. Adherence to GFD was assessed using the CD adherence test (CDAT) and GFD score (GFD-S). Knowledge, attitudes, experiences, symptoms, and QoL were assessed using existing questionnaires. A multivariate logistic regression was performed. RESULTS: Overall, 116 patients with CD were included (48 ± 16 y; 70% female). Based on the CDAT, 58 patients (50%) were adequate adherers, but 86 patients (74%) were adequate adherers according to GFD-S. When adherence was measured using the CDAT, being female was associated with lower odds of adherence (odds ratio [OR]: 0.36; P = 0.028), and better emotional wellbeing was associated with higher odds of adherence (OR: 1.19; P < 0.001). When adherence was measured using GFD-S, membership in a support group (OR: 6.17; P = 0.002), stronger beliefs about the chronicity of CD (OR: 1.15; P = 0.059), and weaker beliefs on accident/chance causing CD (OR: 1.94; P = 0.05) were associated with greater odds of adherence. Difficulties when eating with family/friends (OR: 0.98; P = 0.005) and weaker beliefs on immunity causing CD (OR: 0.77; P = 0.031) were associated with lower odds of adherence. CONCLUSIONS: The association between gender, attending support groups, attitudes, experiences, and QoL with adherence to a GFD should be considered by health care professionals managing patients with CD.

DIY productive failure: boosting performance in a large undergraduate biology course.

Students in first-year university courses often focus on mimicking application of taught procedures and fail to gain adequate conceptual understanding. One potential approach to support meaningful learning is Productive Failure (PF). In PF, the conventional instruction process is reversed so that learners attempt to solve challenging problems ahead of receiving explicit instruction. While students often fail to produce satisfactory solutions (hence "Failure"), these attempts help learners encode key features and learn better from subsequent instruction (hence "Productive"). Effectiveness of PF was shown mainly in the context of statistical and intuitive concepts, and lessons that are designed and taught by learning scientists. We describe a quasi-experiment that evaluates the impact of PF in a large-enrollment introductory university-level biology course when designed and implemented by the course instructors. One course-section (295 students) learned two topics using PF; another section (279 students) learned the same topics using an active learning approach, which is the standard in this course. Performance was assessed on the subsequent midterm exam, after all students had ample opportunities for practice and feedback, and after some time has elapsed. PF students scored nearly five percentage-points higher on the relevant topics in the subsequent midterm exam. The effect was especially strong for low-performing students. Improvement on the final exam was only visible for low-performing students. We describe the intervention and its potential to transform large introductory university courses.

A Randomized Crossover Trial of Conventional vs Virtual Chromoendoscopy for Colitis Surveillance: Dysplasia Detection, Feasibility, and Patient Acceptability (CONVINCE).

BACKGROUND: Chromoendoscopy (CE) is the recommended surveillance technique for colitis, but uptake has been limited and the literature provides scant information on patient experience (PE); imperative to adherence to surveillance programmes. Virtual CE (VCE) by Fujinon Intelligent Colour Enhancement digitally reconstructs mucosal images in real time, without the technical challenges of CE. We performed a multifaceted randomized crossover trial (RCT) to evaluate study feasibility and obtain preliminary comparative procedural and PE data. METHODS: Patients were randomized to undergo either CE with indigo carmine or VCE as the first procedure. After 3-8 weeks, participants underwent colonoscopy with the second technique. Patient recruitment/retention, missed dysplasia, prediction of dysplasia, and contamination (memory/sampling of the first procedure) were recorded. PE was assessed by validated questionnaires, and pain was assessed using a visual analog scale (mm). RESULTS: Sixty patients were recruited, and 48 patients (first procedure: 23 VCE, 25 CE) completed the trial (retention 80%) with no episodes of contamination. Eleven dysplastic lesions were detected in n = 7/48 (14.5%). VCE missed 1 lesion, and CE missed 2 lesions in n = 2 (data of VCE vs CE, respectively, for dysplasia diagnostic accuracy: 93.94% [85.2%-98.32%] vs 76.9% [66.9%-98.2%]; examination time [minutes]: 14 +/- 4 vs 20 +/- 7 (95% confidence interval, 3.5 to 8; P < 0.001); pain (mm): 27.4 +/- 17.5 vs 34.7 +/- 18; patient preference: 67% [n = 31] vs 33% [n = 15] in n = 46; P < 0.001). CONCLUSIONS: This is the first RCT to include validated PE in a colitis surveillance program. VCE is safe, technically easier, quicker, and more comfortable test, with dysplasia detection at least as good as that of CE, overcoming many barriers to the wider adoption of CE. This trial may serve as a successful foundation for a a multicenter trial to confirm the value of VCE for colitis surveillance.

Golimumab: early experience and medium-term outcomes from two UK tertiary IBD centres.

OBJECTIVE: To gain an understanding of the effectiveness of golimumab in a 'real-world' setting. DESIGN: Retrospective cohort study using prospectively maintained clinical records. SETTING: Two UK tertiary IBD centres. PATIENTS: Patients with ulcerative colitis (UC) were given golimumab at Guy's & St Thomas and King's College Hospitals between September 2014 and December 2016. INTERVENTION: Golimumab, a subcutaneously administered antitumour necrosis factor agent. MAIN OUTCOME MEASURES: Clinical disease activity was assessed at baseline and at the first clinical review following induction therapy using the Simple Clinical Colitis Activity Index (SCCAI). Response was defined as an SCCAI reduction of 3 points or more. Remission was defined as an SCCAI of less than 3. RESULTS: Fifty-seven patients with UC completed golimumab induction therapy. Paired preinduction and postinduction SCCAI values were available for 31 patients and fell significantly from 7 (2-19) to 3 (0-11) (p<0.001). To these 31, an additional 13 patients who did not have paired SCCAI data but stopped treatment due to documented 'non-response' in the opinion of their supervising clinician, were added. Among this combined cohort, 23/44 (52%) had a clinical response, 15/44 (34%) achieved remission and 13/44 (30%) achieved corticosteroid-free remission.Faecal calprotectin and CRP fell (FC: pre-induction: 1096 (15-4800) µg/g, post-induction: 114 (11-4800) µg/g, p = 0.011; n = 20; CRP: pre-induction: 4 (1-59) mg/L, post-induction: 2 (1-34) mg/L, p = 0.01 for n = 43). Post-induction endoscopy was carried out in 23 patients and a mucosal healing (Mayo 0 or 1) rate of 35% was observed. CONCLUSIONS: Our experience mirrors previously reported real-world cohorts and demonstrates similar outcomes to those observed in randomised controlled trials. These data demonstrate a meaningful reduction in clinical, biochemical and endoscopic disease activity as well as a steroid-sparing effect in patients with previously refractory disease.

Outcomes of Endoscopic Resections of Large Laterally Spreading Colorectal Lesions in Inflammatory Bowel Disease: a Single United Kingdom Center Experience.

Background: The SCENIC consensus statement recommends endoscopic resection of all visible dysplasia in inflammatory bowel disease, but patients with large or complex lesions may still be advised to have colectomy. This article presents outcomes for large nonpolypoid resections associated with colitis at our institution. Methods: Data including demographics, clinical history, lesion characteristics, method of resection, and postresection surveillance were collected prospectively in patients with visible lesions within colitic mucosa from January 2011 to November 2016. Resection techniques included endoscopic mucosal resection , endoscopic submucosal dissection (ESD), and hybrid ESD. Surveillance with magnification chromoendoscopy was performed at 3 months, 1-year postresection, and annually thereafter. Results: Fifteen lesions satisfied the inclusion criteria in 15 patients. Mean lesion size was 48.3+/-21.7 (20-90) mm. All lesions were non-polypoid with distinct margins and no ulceration. 73% lesions were scarred of which 64% had undergone prior instrumentation. En bloc resection was achieved in n=6. Presumed endoscopic diagnosis was confirmed histopathologically in all resected lesions. One case of perforation and another with bleeding were both managed endoscopically. Median follow-up was 28 months (12-35) with no recurrence. Conclusion: This cohort series demonstrates that endoscopic resection of large non-polypoid lesions associated with colitis is feasible and safe using an array of resection methods supporting the role of advanced endoscopic therapeutics for the management of colitis associated dysplasia in a western tertiary endoscopic center.

Vedolizumab: early experience and medium-term outcomes from two UK tertiary IBD centres.

OBJECTIVE: To gain an understanding of the efficacy of vedolizumab in a 'real-world' setting. DESIGN: Retrospective cohort study using prospectively maintained clinical records. SETTING: Two UK tertiary inflammatory bowel disease (IBD) centres. PATIENTS: Patients with IBD commenced on vedolizumab at Guy's & St Thomas' and King's College Hospitals during November 2014-November 2015. INTERVENTION: Vedolizumab, a monoclonal antibody to α-4 ß-7 integrins that selectively inhibit leucocyte migration into the gut. MAIN OUTCOME MEASURES: Clinical disease activity was assessed at baseline, weeks 14 and 30 using Harvey-Bradshaw Index (HBI) for Crohn's disease (CD) and Simple Clinical Colitis Activity Index (SCCAI) for ulcerative colitis (UC). Response was defined as HBI or SCCAI reduction ≥3. Remission was defined as HBI <5 or SCCAI <3. Continuous data are summarised as medians, followed by range. RESULTS: Fifty patients were included: 27 CD, 20 UC and 3 IBD-U (included in the UC group for analysis). At baseline visit, the median HBI was 8 (1-16) and SCCAI was 6 (0-15). At week 14, these values had fallen to 5 (0-15) (p=0.117) and 4 (0-10) (p=0.005), respectively. Additionally, week 30 data were available for 19 patients (9 CD, 10 UC). The clinical disease activity scores at that point were HBI 2 (0-7) (p=0.039) and SCCAI 2 (0-10) (p=0.023). At baseline, 37 (74%) of the 50 patients had clinically active disease. Of the patients with active disease, 22 (59%) responded and 14 (38%) achieved remission at week 14. CONCLUSIONS: Our early experience with vedolizumab demonstrates a clear benefit in terms of disease control as well as a steroid-sparing effect in a cohort, which included patients with complex and previously refractory disease.

Early change in faecal calprotectin predicts primary non-response to anti-TNFα therapy in Crohn's disease.

OBJECTIVE: The early identification of primary non-response to anti-TNFα therapy facilitates the timely management of patients with Crohn's disease (CD). A recent, pilot study to detect prognostic markers of early response to anti-TNFα therapy identified the two genes coding for the calprotectin subunits (S100A8, S100A9) to be among the most highly expressed gene transcripts in non-responders. This study tests the hypothesis that measurements of faecal calprotectin (FCAL) pre- and post-anti-TNFα induction can predict primary non-response. METHODS: Retrospective study of 32 CD patients treated over a two-year period. Outcomes were assessed at 6 months based on clinical activity scores and the use of corticosteroids: (a) remission: Harvey-Bradshaw index (HBI) < 5, off corticosteroids >2 months; (b) response: drop in HBI >3, off corticosteroids; (c) non-response: ΔFCAL (and ΔCRP, respectively) was calculated as (FCAL post-induction - FCAL pre-induction) × 100/FCAL pre induction. RESULTS: At 6 months, 23 (72%) patients had responded (median (interquartile range) HBI: 4 (3-5), FCAL: 55 (27-146)), 17 (73%) of whom were in remission [HBI: 3 (2.5-4) and FCAL: 42 (16-115)]. There was a significant difference in the ΔFCAL from baseline to post-induction in the three groups (p < 0.0001). Comparing non-responders to combined response and remission groups, the AUC of ΔFCAL to predict outcome at 6 months was 0.97. Using ROC analysis, a Δ70% returned a sensitivity and specificity of 99% and 96%, respectively (likelihood ratio, LR= 23). ΔCRP did not predict 6 months outcomes. CONCLUSIONS: A drop in FCAL <70% after induction predicts primary non-response to anti-TNFα in CD.

Spontaneous cerebrospinal fluid leak following a pilates class: a case report.

INTRODUCTION: A spinal cerebrospinal fluid leak is the most common cause of spontaneous intracranial hypotension which is an uncommon but increasingly recognized cause of headache. This article describes the first reported case of pilates being associated with a spontaneous spinal cerebrospinal fluid leak whilst also highlighting the key information about spontaneous cerebrospinal fluid leaks that will be useful to the general clinician. CASE PRESENTATION: We present the case of a 42-year-old Caucasian woman who developed a low-pressure headache following a pilates class. A computed tomography scan of her head demonstrated bilateral chronic subdural hematomas and cerebellar descent. Magnetic resonance imaging of her spine revealed the presence of extensive extradural cerebrospinal fluid collections. She responded to conservative management and repeat neuroimaging after symptom resolution revealed no abnormalities. CONCLUSIONS: Awareness and early recognition of spontaneous intracranial hypotension is important to prevent unnecessary investigations and delay in treatment. Pilates may be a risk factor for the development of a spontaneous cerebrospinal fluid leak.

HLA-DQA1-HLA-DRB1 variants confer susceptibility to pancreatitis induced by thiopurine immunosuppressants.

Pancreatitis occurs in approximately 4% of patients treated with the thiopurines azathioprine or mercaptopurine. Its development is unpredictable and almost always leads to drug withdrawal. We identified patients with inflammatory bowel disease (IBD) who had developed pancreatitis within 3 months of starting these drugs from 168 sites around the world. After detailed case adjudication, we performed a genome-wide association study on 172 cases and 2,035 controls with IBD. We identified strong evidence of association within the class II HLA region, with the most significant association identified at rs2647087 (odds ratio 2.59, 95% confidence interval 2.07-3.26, P = 2 × 10(-16)). We replicated these findings in an independent set of 78 cases and 472 controls with IBD matched for drug exposure. Fine mapping of the HLA region identified association with the HLA-DQA1*02:01-HLA-DRB1*07:01 haplotype. Patients heterozygous at rs2647087 have a 9% risk of developing pancreatitis after administration of a thiopurine, whereas homozygotes have a 17% risk.

Dense genotyping identifies and localizes multiple common and rare variant association signals in celiac disease.

Using variants from the 1000 Genomes Project pilot European CEU dataset and data from additional resequencing studies, we densely genotyped 183 non-HLA risk loci previously associated with immune-mediated diseases in 12,041 individuals with celiac disease (cases) and 12,228 controls. We identified 13 new celiac disease risk loci reaching genome-wide significance, bringing the number of known loci (including the HLA locus) to 40. We found multiple independent association signals at over one-third of these loci, a finding that is attributable to a combination of common, low-frequency and rare genetic variants. Compared to previously available data such as those from HapMap3, our dense genotyping in a large sample collection provided a higher resolution of the pattern of linkage disequilibrium and suggested localization of many signals to finer scale regions. In particular, 29 of the 54 fine-mapped signals seemed to be localized to single genes and, in some instances, to gene regulatory elements. Altogether, we define the complex genetic architecture of the risk regions of and refine the risk signals for celiac disease, providing the next step toward uncovering the causal mechanisms of the disease.

A meta-analysis of genome-wide association scans identifies IL18RAP, PTPN2, TAGAP, and PUS10 as shared risk loci for Crohn's disease and celiac disease.

Crohn's disease (CD) and celiac disease (CelD) are chronic intestinal inflammatory diseases, involving genetic and environmental factors in their pathogenesis. The two diseases can co-occur within families, and studies suggest that CelD patients have a higher risk to develop CD than the general population. These observations suggest that CD and CelD may share common genetic risk loci. Two such shared loci, IL18RAP and PTPN2, have already been identified independently in these two diseases. The aim of our study was to explicitly identify shared risk loci for these diseases by combining results from genome-wide association study (GWAS) datasets of CD and CelD. Specifically, GWAS results from CelD (768 cases, 1,422 controls) and CD (3,230 cases, 4,829 controls) were combined in a meta-analysis. Nine independent regions had nominal association p-value <1.0 x 10⁻5 in this meta-analysis and showed evidence of association to the individual diseases in the original scans (p-value < 1 x 10⁻² in CelD and < 1 x 10⁻³ in CD). These include the two previously reported shared loci, IL18RAP and PTPN2, with p-values of 3.37 x 10⁻8 and 6.39 x 10⁻9, respectively, in the meta-analysis. The other seven had not been reported as shared loci and thus were tested in additional CelD (3,149 cases and 4,714 controls) and CD (1,835 cases and 1,669 controls) cohorts. Two of these loci, TAGAP and PUS10, showed significant evidence of replication (Bonferroni corrected p-values <0.0071) in the combined CelD and CD replication cohorts and were firmly established as shared risk loci of genome-wide significance, with overall combined p-values of 1.55 x 10⁻¹° and 1.38 x 10⁻¹¹ respectively. Through a meta-analysis of GWAS data from CD and CelD, we have identified four shared risk loci: PTPN2, IL18RAP, TAGAP, and PUS10. The combined analysis of the two datasets provided the power, lacking in the individual GWAS for single diseases, to detect shared loci with a relatively small effect.