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Recognition and assessment of celiac disease.

Celiac disease is an immune-mediated disorder causing chronic inflammation of the small intestinal mucosa and a range of systemic symptoms, and it is far more common than most clinicians realize. Because of its many, often nonspecific manifestations, the disease is underdiagnosed despite affecting between 0.5% and 1% of the population, with a prevalence that might be twice as high in women as in men.

A recent guideline from the British National Institute for Health and Clinical Excellence (NICE) (May 2009) examines the challenging diagnostic considerations of celiac disease, updating and expanding on a 2004 guideline from the National Institutes of Health (NIH Consens. State. Sci. Statements 2004;21; 1-22).

Candidates for Assessment

The diversity of clinical manifestations of celiac disease makes the initial selection of patients who warrant assessment difficult. Screening should be carried out for any patient with gastrointestinal symptoms that include chronic or intermittent diarrhea, prolonged or unexplained nausea or vomiting, and recurrent abdominal pain, cramping, or distension. Also prompting a work-up are symptoms resulting from gastrointestinal dysfunction, such as failure to thrive in children, prolonged fatigue, sudden or unexpected weight loss, or unexplained iron-deficiency anemia.

Because of increased prevalence rates of celiac disease in patients with many comorbidities, especially autoimmune diseases, clinicians should screen for celiac disease in individuals with dermatitis herpetiformis, irritable bowel syndrome, autoimmune thyroid disease, and type 1 diabetes mellitus. Screening is also recommended for first-degree relatives of celiac disease patients, as the prevalence of the disorder is high in this group at 4%-12%.

Although numerous additional diseases have been associated with celiac disease, the evidence supporting these links is relatively weak, leading to the recommendation to "consider serological testing." These loosely associated diseases include, but are not limited to, Addison's disease, amenorrhea, depression / bipolar disorder, Down syndrome, epilepsy, recurrent miscarriage, lymphoma, Turner syndrome, and autoimmune hepatitis or myocarditis.

Diagnostic Methodology

Confusion has historically existed regarding the optimal diagnostic workup for celiac disease. An initial barrier to diagnostic testing is that the entire workup must be carried out while the patient is consuming a gluten-containing diet. For individuals who have already eliminated dietary gluten because of a presumptive diagnosis of celiac disease, it is necessary to reintroduce the grain antigen into the diet on a daily basis for at least 6 weeks. A gluten-free diet should not be initiated or resumed until the full course of diagnostic testing has been completed.

NICE recommends IgA tissue transglutaminase (tTGA) serology as the first-line test, with IgA endomysial antibody (EMA) as a follow-up if tTGA results are equivocal. If IgA serologies are negative despite high suspicion for the disease, IgA deficiency should be investigated, with subsequent IgG, tTGA, and EMA testing if an IgA deficiency is discovered.

Confirmatory testing is indicated based on the results of the initial tTGA serology. Consultation with a gastroenterologist is required for small bowel endoscopy with biopsy. Multiple biopsy sites are required, as intestinal involvement may be intermittent. The most definitive appearance on biopsy is villous atrophy, with intraepithelial lymphocytes and crypt hyperplasia as associated supportive findings. A negative small intestinal biopsy with positive serologies raises a diagnostic dilemma. Although no firm evidence-based recommendation exists for this situation, reasonable options are a repeat small bowel biopsy in several months, periodic repeat serologies, and the trial of a gluten-free diet.

Historically, other serological testing modalities have been employed in the diagnosis of celiac disease. However, the institute recommends against screening with antigliadin antibody (AGA), as this test is less sensitive and specific than tTGA or EMA. Also not indicated for routine initial work-up is human leukocyte antigen (HLA) DQ2/DQ8 testing. This marker is seen in more than 97% of individuals with celiac disease, compared with approximately 40% of the general population, making its negative predictive value excellent in complex, equivocal diagnostic cases. The absence of HLA DQ2/DQ8 essentially rules out celiac disease, but the use of this genetic test for screening is not indicated.

Consequences of Failed Diagnosis

Several studies cited by both the American and British guidelines indicated a higher risk of several diseases in patients with diagnosed and undiagnosed celiac disease. These included fractures, low birth weight, decreased intrauterine growth, and malignancy (small bowel cancer, Hodgkin's disease, and non-Hodgkin's lymphoma). However, no causative link was found between these conditions and celiac disease, and no improvement in the rates of these comorbidities was found when a gluten-free diet was introduced. Clinical ramifications of these disease relationships remain to be determined.

The Bottom Line

Celiac disease is a common, treatable condition. Serological testing using tTGA, and possibly EMA, should be performed in patients with persistent gastrointestinal symptoms, a family history of celiac disease, or other associated conditions, especially autoimmune diseases. Those individuals with positive blood tests should be referred to a gastroenterologist for a small bowel biopsy to confirm the diagnosis of celiac disease.

All testing must be performed while the patient is consuming a gluten-containing diet to be of diagnostic utility.

References

* Recognition and Assessment of Coeliac Disease. NICE Clinical Guideline 86. National Institute for Health and Clinical Excellence. May 2009.

* NIH Consensus Statement on Celiac Disease. NIH Consens. State. Sci. Statements 2004June 28-30; 21(1): 1-22.

BY NEIL S. SKOLNIK, M.D., AND EVAN E. NEFT, M.D.

DR. SKOLNIK is an associate director of the Family Medicine Residency Program at Abington (Pa.) Memorial Hospital. DR. NEFT is a third-year resident in the program.
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Title Annotation:CLINICAL GUIDELINES FOR FAMILY PHYSICIANS
Author:Skolnik, Neil S.; Neft, Evan E.
Publication:Family Practice News
Article Type:Disease/Disorder overview
Geographic Code:1USA
Date:Aug 1, 2010
Words:897
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