Sheila E. Crowe, MD, FACG

Transcription

1 1A: Upper Gut Celiac Disease: When to Look and How? Sheila E. Crowe, MD, FACG Learning Objectives At the end of this presentation, the successful learner should be able to: Identify the many groups of individuals at risk of celiac disease. Determine appropriate methods to evaluate and diagnose individuals at risk of having celiac disease. Develop an approach to investigating patients already on a gluten-free diet without a prior diagnosis of celiac disease. Evaluate patients who fail treatment for celiac disease (non-responsive celiac disease). Overview of Celiac Disease Celiac disease, also referred to as gluten-sensitive enteropathy or the less preferred term of celiac sprue, is a chronic disorder that is readily recognized when it presents in its classical form with diarrhea, bloating, flatulence, weight loss, and evidence of malabsorption. Withdrawal of immunogenic grains including wheat, rye and barley from the diet of affected patients results in a rapid clinical improvement and a slower return of small bowel histology to normal. Over the past two decades, it has become increasingly evident that celiac disease can present in many other ways including non-specific gastrointestinal complaints, anemia, recurrent miscarriages, neuropsychiatric disorders and osteopenic bone disease. In addition, celiac disease may complicate other disorders, particularly autoimmune endocrine and connective tissue diseases. Celiac disease is a unique disorder representing both a form of food allergy and an autoimmune disease. Until relatively recently, celiac disease was thought to be rare and primarily a disease of childhood, even a disease which one could grow out of. It is thought that the prevalence of celiac disease in genetically susceptible populations including those in the United States is as high as approximately 1:100 (1%). It is now recognized that celiac disease is common, affecting both adults and children, and is a lifelong condition that is treated almost exclusively by dietary measures. Most patients present in adult life and the average age of diagnosis is in the fifth decade of life. Clinical Presentations (Tables 1 and 2) The classical presentation of celiac disease includes diarrhea, failure to thrive or weight loss, abdominal distention, flatulence, and fatigue. However, there are many less dramatic or classical presentations of celiac disease that respond equally well to the institution of a gluten-free diet (Table 1). These include iron-deficiency anemia, folate deficiency, dermatitis herpetiformis, osteopenic bone disease, as well as relatively non-specific gastrointestinal (GI) symptoms. Studies as well as anecdotal experience indicate that many patients remain undiagnosed for years in spite of unexplained symptoms or abnormal blood tests. Celiac disease is increased in frequency in various autoimmune conditions (Table 2) including insulin-dependent diabetes mellitus, autoimmune thyroid disease, ulcerative colitis, primary biliary cirrhosis, primary sclerosing cholangitis, and Sjogren s syndrome. A significant number of studies have examined the incidence of celiac disease in populations of patients with type I diabetes mellitus (3 to 8%) yet relatively few patients were diagnosed prior to conducting screening tests for celiac disease. In addition to the recognized autoimmune hepatobiliary diseases associated with celiac disease, elevated transaminases are associated with celiac disease and typically respond to a gluten-free diet. A variety of gynecologic and obstetrical presentations are associated with celiac disease including delayed menarche, infertility, miscarriages, intrauterine growth retardation and low birth weight. Neuropsychiatric disorders that have been associated with celiac disease range from peripheral neuropathy, ataxia, schizophrenia, to cognitive deficits and hyperactivity-attention deficit disorder. A number of other conditions are associated with celiac disease including Turner s syndrome, Down s syndrome, IgA deficiency, and IgA nephropathy (Table 2). Pathogenesis including Genetic Factors Inappropriate T-cell responses to ingested gluten in genetically predisposed individuals result in the intestinal injury that characterizes celiac disease. Prolamins (gliadin in wheat, secalin in rye, and hordein in barley, collectively referred to as gluten) have been identified as the component of those grains capable of inducing damage in celiacs. Most recent studies suggest that avenin in oats does not induce immunoreactivity although there are reports to suggest that some T cells may react to oat-derived peptides. Genetic factors are suggested by the 70% concordance rate in identical twins and a prevalence of 10-15% in first-degree relatives. HLA studies indicate that most celiacs possess the extended haplotype, DR3-DQ2 or less often, DR5/7-DQ2. The DQ2 alpha/beta heterodimer is encoded by the alleles DQA1*0501, DQB1*0201. Some celiac patients have DR4- DQ8 encoded by the DQA1*0301, DQB1*0302 alleles. Since 12 1A: Upper Gut

2 Table 1: Presentations of celiac disease classical celiac disease of childhood Late onset GI symptoms Often mistaken for IBS Can be non-specific Extraintestinal presentations Dermatitis herpetiformis Iron deficiency Folate deficiency Osteopenic bone disease Chronic fatigue Neuropsychiatric manifestations Short stature Infertility Obstetrical complications Asymptomatic celiac disease Often in relatives Latent celiac disease over one-third of the U.S. population has these haplotypes, this suggests that additional susceptibility genes are required for the development of celiac disease. Antigen presenting cells bearing these HLA haplotypes present gliadin peptides to intestinal mucosal T cells, which mediate the immune response resulting in intestinal damage through cytokines such as IL-15 and interferon gamma. The deamidating activity of tissue transglutaminase (ttg, also known as transglutaminase 2, TG2) modifies gliadin to become the dominant alpha-gliadin T-cell epitope. Diagnostic Tests Serological Tests A variety of tests are available that can be used in celiac disease for diagnosis and screening. Antigliadin antibodies (AGA) measured by enzyme-linked immunosorbent assays are reasonably sensitive although not highly specific tests for the presence of celiac disease. False positive AGA have been reported in other conditions including small bowel bacterial overgrowth and various other GI conditions as well as in healthy individuals. This is particularly true for IgG AGA which has a high false positive rate. IgA AGA is more specific but its sensitivity (~80%) is not high. AGA antibodies are no longer recommended for adults in the detection of celiac disease given their lower sensitivity and specificity compared to antibodies to tissue transglutaminase (ttg). The most specific antibody found in the sera of untreated celiac patients is the endomysial antibody (EMA). This IgA antibody reacts with the endomysial lining of microfibrils and is assayed by immunofluorescence using monkey esophagus Table 2: Conditions associated with celiac disease autoimmune endocrine disorders Insulin-dependent diabetes mellitus Autoimmune thyroid disease Autoimmune adrenal disease Autoimmune connective tissue disorders Sjogren s syndrome Rheumatoid arthritis Systemic lupus erythematosis Hepatobiliary conditions Primary sclerosing cholangitis Primary biliary cirrhosis Autoimmune cholangitis Elevated transaminases Other gastrointestinal disorders Lymphocytic gastritis Microscopic colitis Miscellaneous conditions IgA deficiency IgA nephropathy Down s syndrome Turner s syndrome or cultured human umbilical vein cells as the substrate. Tissue transglutaminase is the antigen to which EMA reacts and sensitive immunoassays using human recombinant ttg are in widespread use. The sensitivity of anti-hr ttg IgA assays varies between 89 to 98% and is also very specific. Given the cost and limited availability of EMA testing, ttg IgA testing is the recommended test for screening for celiac disease. Recently, it has been shown that IgA and IgG antibodies to deamidated gliadin peptides (DGP) are also useful in the detection of celiac disease. Deamidation of gliadin by the ttg enzyme creates a more immunogenic form of gliadin and thus antibodies to DGP reflect active celiac disease. However, a recent meta-analysis suggests that ttg IgA remains a better test than the DGP antibody assays. Antibody tests should not replace intestinal morphology for making a diagnosis of celiac disease but in those unable or unwilling to undergo endoscopy, the presence of a positive EMA or high titer IgA ttg is most suggestive of the diagnosis of celiac disease. These antibody assays are useful in monitoring compliance since levels will decrease on a glutenfree diet and increase after the ingestion of gluten. ttg or EMA can also play a role in the timing of endoscopy and biopsy during a gluten challenge used in diagnosing patients who had been on a gluten-free diet without an initial proven diagnosis of celiac disease. Another potential role for the antibody tests is in screening higher risk individuals including 1A: Upper Gut 13

3 Table 3: Settings in which there is an increased risk of celiac disease 1st degree relatives of patients with celiac disease (10-15%) 2nd degree relatives of patients with celiac disease ( %) Type I DM (2-5% adults, 3-8% children) Autoimmune thyroid disease (3%) Symptomatic iron deficiency anemia (10-15%) Asymptomatic iron deficiency anemia (2-9%) Microscopic colitis (15-27%) IBS (3.4%) Osteoporosis (1-3%) Elevated transaminases (1.5-9%) Autoimmune hepatitis (3-6%) Primary biliary cirrhosis (0-6%) Down s syndrome (3-12%) Chronic fatigue syndrome (2%) Unexplained infertility (2-4%) relatives of celiac patients (ideally those who are known to be HLA DQ2 or DQ8 positive) and those with autoimmune conditions including Type I diabetics. (See Table 3 for a list of settings in which there is a higher likelihood of celiac disease). The optimal antibody or panel of antibodies depends in part on the prevalence in the population being screened but in general, ttg IgA is recommended in the initial assessment. Intestinal biopsy specimens should be obtained in all individuals with elevated EMA or ttg antibodies wherever possible. Until recently, a total IgA level was often checked in conjunction with a ttg IgA level to exclude IgA deficiency as a cause for a false negative screening test. IgA deficiency is suggested by a very low titer ttg IgA level and a total IgA level does not need to be routinely ordered. However, if the normal range for IgA ttg is narrow (i.e., between 0 and 3) versus a wider range (such as 0-20) then it is difficult to identify results that indicate IgA deficiency. Endoscopy Findings and Histopathology Intestinal biopsies remain the only means by which a diagnosis of celiac disease can be made since all serological tests have a false positive rate with recent studies suggesting specificity of 98% for ttg IgA. However, low titer antibody levels are more likely to be a false positive result. In most instances, biopsies from the duodenum using a standard upper GI endoscope are sufficient to make the diagnosis. Since celiac disease can be patchy, it is recommended that 4-6 biopsies are obtained with at least one biopsy from the duodenal bulb as recent studies in both children and adults indicate that biopsies from the bulb increase the diagnostic yield of histology. Targeting biopies from endoscopically abnormal mucosa including areas of scalloping of folds or fissuring of mucosa between the folds is recommended. However, while these endoscopic features have a high positive predictive value for detecting celiac disease, the sensitivity of these findings is not high. Thus, the absence of endoscopic findings should not preclude procurement of biopsies in anyone in whom celiac disease is being considered. The diagnosis of celiac disease still requires a characteristic appearance on histological examination of mucosal biopsy specimens obtained from the small intestine. These findings include varying degrees of villous atrophy, a change in the normal columnar appearance of the absorptive epithelium with crypt hyperplasia and increased numbers of IEL and lamina propria mononuclear cells. More minor degrees of histopathology may be missed on routine examination since the earliest changes are an increase in IEL. These features are not specific for celiac disease in that some or all of the histological findings can be found in tropical sprue, small intestinal bacterial overgrowth, viral gastroenteritis, intestinal lymphoma, and severe acid-induced injury associated with a gastrinoma. Newer endoscopic technology including higher resolution imaging and chromendoscopy can be helpful in differentiating abnormal mucosa with fissuring, notching or scalloping and loss of villi from areas of more normal appearing mucosa. However, endoscopic findings are not sensitive although they are more specific for the diagnosis of celiac disease. With the availability of improved serologic testing, a second set of biopsies to confirm histological improvement or complete healing on a gluten-free diet is not necessary in most instances. A second endoscopy with biopsies should be reserved for patients failing to improve clinically or serologically in spite of adequate dietary treatment. The clinical improvement is rapid while months up to years are usually needed before complete histological resolution is seen. Genetic Testing As discussed above, HLA studies indicate that the most celiacs possess the extended haplotype, DR3-DQ2 or less often, DR5/7-DQ2. Some celiac patients have DR4-DQ8. Nearly all celiacs bear one of these three haplotypes, which has led to the development of new assays for diagnosis and screening. PCR assays to detect a restricted set of HLA antigens (HLA DQ2 and DQ8) are available and can be helpful in defining those at risk of developing celiac disease. Such assays can be performed on cells in a blood sample or a cheek swab. Although the prevalence of these HLA haplotypes is approximately 35-40% of the North American population, celiac disease only occurs in the subset bearing at least one of these two genes. Thus, such testing can be useful in determining who should undergo a gluten challenge and also for screening family members. Family members of a celiac patient who are also HLA DQ2 or DQ8 positive have a 20-30% likelihood of having or developing celiac disease. 14 1A: Upper Gut

4 Strategies for Confirming a Diagnosis in a Subject Already on Dietary Therapy Increasing numbers of patients are labeled as having celiac disease based on serological testing or even clinical presentation alone. A beneficial response to a gluten-free diet (GFD) does not indicate celiac disease as it is not unusual for patients with irritable bowel syndrome and other conditions to benefit from such a diet. One study reported that a positive response to a GFD correctly predicts celiac disease about a third of the time. Individuals who have been diagnosed as having celiac disease without initial biopsy specimens obtained while on a gluten-containing diet should undergo gluten challenge to confirm the diagnosis (Table 4). Firstly, if serology has never been performed, a ttg IgA should be checked in case the patient does have the disease but has not been on adequate therapy. If this is elevated, duodenal biopsies should be obtained. In most instances, serology was negative to begin with or only a very non-specific antibody IgG AGA was elevated. Ideally, HLA screening can be performed initially to determine if the patient is even at risk of celiac disease. Those without susceptibility genes can be counseled that their symptoms are very unlikely to be celiac disease. Most often, such cases have underlying functional bowel disorders or a form of gluten sensitivity without celiac disease, an emerging entity for which specific diagnostic criteria and unifying clinical description does not yet exist. A so-called gluten challenge has been recommended to enhance the sensitivity of detecting celiac disease by serology and intestinal biopsies but given the availability of genetic testing for HLA DQ2 and D8-containing haplotypes that are necessary (but not sufficient) for the development of celiac disease, it is now recommended that patients already on a long-term gluten-free diet have such testing before undergoing a gluten challenge. HLA DQ assays are PCR tests of cells in a blood sample or a cheek swab that assess for the presence of HLA DQ2 and DQ8. A gluten challenge comprises ingestion of the equivalent of 4 slices of bread a day until a patient develops symptoms, positive serological tests and/or other findings suggestive of celiac disease. A lower dose of gluten is initially recommended in case the patient is very sensitive to gluten. Although there are limited studies to guide the practice, most experts would recommend obtaining intestinal biopsies after 6 months on a gluten-containing diet even if the patient remains well, seronegative and without laboratory abnormalities that can occur in celiac disease. If the patient has been gluten-free for many years, a longer challenge may be needed. Table 4: Strategy to diagnose patients on a gluten-free diet without a confirmed diagnosis of celiac disease: A gluten challenge Who to challenge: Patients started on gluten-free diet (GFD) without confirmatory histology Patients with an equivocal diagnosis or equivocal response to GFD What to challenge with: Diet containing gradually increasing amounts of gluten Final amount will vary according to patient sensitivity Minimum of 10 g gluten (2 slices bread) a day Maximum of as much gluten as tolerated Standard is 4 slices whole wheat bread a day How long to challenge: Initial period of 2 to 6 weeks before checking EMA and/or ttg Continue challenge if seronegative and symptom free at 2-6 weeks Recheck serology at 1-3 monthly intervals Monitored challenge stopped at 6 months if seronegative and symptom free When to perform endoscopy and small bowel biopsy: When diarrhea or malabsorptive symptoms develop When EMA and/or ttg become positive At 6 months in some instances of no response to challenge Other considerations: Avoid challenges in patients reporting severe reactions to gluten/wheat After long term GFD, expect a prolonged time to develop a response to gluten Elderly and very young patients are not ideal candidates Many patients do not want to undergo challenge HLA DQ2 and DQ8 screening will help determine whom to challenge Non-responsive Celiac Disease A large number of conditions can contribute to non-responsiveness to a gluten-free diet. However, since intentional or unintentional lack of adherence to a gluten-free diet is the most common cause of failure to respond, it is important to carefully review the diet and any other ingested items including medications to ensure that gluten is completely excluded from the diet. Confirming the diagnosis of celiac disease is also very important especially when the pathology report does not describe the characteristic features of celiac disease, which include increased intraepithelial lymphocytes, varying degrees of villous atrophy and increased chronic inflammatory cells in the lamina propria. An incorrect diagnosis of celiac disease can also result in failure to respond to dietary therapy. 1A: Upper Gut 15

5 Other causes of non-responsive celiac disease include conditions that can complicate or coexist with celiac disease such as microscopic colitis, lactose intolerance, small intestinal bacterial overgrowth, and pancreatic insufficiency. Once it is established that the more common causes of nonresponsive celiac disease have been excluded then evaluation for possible refractory celiac disease and malignancies that can rarely complicate celiac disease (enteropathy associated T cell lymphoma, intestinal adenocarcinoma) can be undertaken. Testing for these conditions include small bowel x-rays, capsule endoscopy, enteroscopy, and CT. References 1. Crowe SE. In the clinic: Celiac disease. Ann Internal Med 2011;154: ITC AGA Institute medical position statement on the diagnosis and management of celiac disease. Gastroenterology 2006;131: AGA Institute technical review on the diagnosis and management of celiac disease. Gastroenterology 2006;131: Statement. NIH Consensus Development Conference on Celiac Disease htm [cited; Available from: gov/cons/118/118cdc_intro.htm.] 5. Rostom A, Dube C, Cranney A, et al. The diagnostic accuracy of serological tests for celiac disease: A systematic review. Gastroenterology 2005,128:S38-S Tursi A, Brandimarte G, Giorgetti GM. Prevalence of antitissue transglutaminase antibodies in different degrees of intestinal damage in celiac disease. J Clin Gastroenterol 2003;36(3): Lewis NR, Scott BB. Meta-analysis: Deamidated gliadin peptide antibody and tissue transglutaminase antibody compared as screening tests for coeliac disease. Aliment Pharmacol Ther 2010;31: Hadithi M, von Blomberg BM, Crusius JB, et al. Accuracy of serologic tests and HLA-DQ typing for diagnosing celiac disease. Ann Intern Med 2007;147: van der Windt DA, Jellema P, Mulder CJ, et al. Diagnostic testing for celiac disease among patients with abdominal symptoms: A systematic review. JAMA 2010;303: Pietzak MM, Schofield TC, McGinniss MJ, Nakamura RM. Stratifying risk for celiac disease in a large at-risk United States population by using HLA alleles. Clin Gastroenterol Hepatol 2009;7: Campanella J, Biagi F, Bianchi PI, et al. Clinical response to gluten withdrawal is not an indicator of coeliac disease. Scand J Gastroenterol 2008;43: Oxentenko AS, Grisolano SW, Murray JA, et al. The insensitivity of endoscopic markers in celiac disease. Am J Gastroenterol 2002;97(4): Shah VH, Rotterdam H, Kotler DP, et al. All that scallops is not celiac disease. Gastrointest Endosc 2000;51(6): Hopper AD, Cross SS, Sanders DS. Patchy villous atrophy in adult patients with suspected gluten-sensitive enteropathy: Is a multiple duodenal biopsy strategy appropriate? Endoscopy 2008;40: A: Upper Gut