A rapid, point-of-care test for deamidated gliadin peptide antibody (DGP) identifies patients with celiac disease with similar levels of sensitivity and specificity as standard serologic analysis of antibodies to tissue transglutaminase (anti-tTG). Use of this test before endoscopy could identify the best candidates for duodenal biopsy analysis, leading to cost savings and reducing unnecessary biopsy procedures, researchers report in the July issue of Clinical Gastroenterology and Hepatology.
Celiac disease is under-diagnosed. Many patients are examined by endoscopy, but celiac disease is missed or not detected. Researchers have recommended collecting biopsy samples from high-risk individuals (with symptoms of diarrhea, weight loss, or anemia) and also patients with positive results from tests for anti-tTG, during endoscopy.
However, in practice, serology test results are not always available at the time of endoscopy. An accurate point-of-care test is needed to identify patients likely to have celiac disease before endoscopy, so biopsies can be collected from the best candidates.
Peter D. Mooney et al evaluated the accuracy of finger prick–based point-of-care tests in the detection of celiac disease and developed an algorithm for diagnosis.
They performed a prospective study of 2 groups of patients with celiac disease evaluated in the UK. In the first part of the study, 55 patients at high risk of celiac disease who tested positive for endomysial antibody were evaluated using the Biocard test (BHR Pharmaceuticals) and the Celiac Quick Test (Biohit Healthcare UK), which measure anti-tTG, and the Simtomax test (Tillotts Pharma, see figure), which measures DGP.
In the second part of the study, 508 consecutive patients who underwent an endoscopy examination for any indication received the DGP test, and also were evaluated using a diagnostic algorithm that incorporates results from the DGP test and data on symptoms. Point-of-care tests were performed at the time of endoscopy; results were compared those from histologic analyses of duodenal biopsy specimens from all patients.
In the first part of the study, the DGP test identified patients with celiac disease with 94.4% sensitivity, the Celiac Quick Test identified patients with 77.8% sensitivity, and the Biocard test identified patients with 72.2% sensitivity.
In the second part of the study, the DGP test identified patients with celiac disease with 92.7% sensitivity, 85.2% specificity, a positive predictive value of 49.2%, and a negative predictive value of 98.7%.
Measurement of serum anti-tTG identified patients with celiac disease with 91.2% sensitivity, 87.5% specificity, a positive predictive value of 53.0%, and a negative predictive value of 98.5%. The authors’ algorithm identified patients with celiac disease with 98.5% sensitivity. They state that its use could reduce duodenal biopsies by 35%.
Mooney et al conclude that the DGP test is a useful, office-based tool for rapid identification of patients at risk for celiac disease who should undergo biopsy analysis. The test could produce significant cost savings—patients found to have celiac could immediately be placed on gluten-free diets, and be subjected to fewer office visits and procedures. An earlier start on a gluten-free diet can reduce complications of celiac disease such as osteoporosis, anemia, and lymphoma. Patients with negative test results would not undergo unnecessary biopsy analyses.
The authors wrote that in lower-prevalence populations, such as the 2% to 4% expected for all endoscopy patients, the positive predictive value will decrease and affect cost savings. However, the negative predictive value will improve in lower-prevalence populations,which is crucial for a screening test.
Thirteen percent of patients in the study cohort were found to have celiac disease; this value was high because the study was performed at a tertiary celiac center.
The authors state that although the DGP test performed well their population, further studies are required in lower-prevalence populations, such as an open-access setting, to assess the true effects of rapid testing before endoscopy.