A point-of-care test for deamidated gliadin peptide antibodies was as sensitive as standard serology in detecting celiac disease, according to a single-center prospective study.
The results suggest that the new test could be used as a rapid serologic assay in outpatient care, which could save costs by reducing office visits and negating the need for duodenal biopsy in some patients, said Dr. Peter Mooney of Royal Hallamshire Hospital in Sheffield, England, and his associates. “Endoscopy is performed in both primary and secondary care in the United States, and the use of this point-of-care test before all procedures has the potential to reduce the numbers of missed cases at endoscopy significantly,” the investigators said.
Celiac disease affects about 0.2%-1.2% of the global population, and about three to four cases go undetected for every case that is diagnosed. Part of the problem is that endoscopists often do not recognize signs of celiac disease and therefore miss the chance to perform duodenal biopsy, the investigators said. A previous algorithm for when to perform duodenal biopsy detected 100% of cases of celiac disease, but relied on serology, which often is not available in clinical practice, the researchers noted (Clin. Gastroenterol. Hepatol. 2015 Jan. 2 [doi: 10.1016/j.cgh.2015.01.010]).
Therefore, they prospectively compared three point-of-care, finger prick–based assays for biomarkers of celiac disease to standard serology and duodenal biopsy. The study groups included 55 endoscopy patients who had tested positive for endomysial antibody and were considered at high risk for celiac disease, and a separate group of 508 patients who were undergoing endoscopy for any reason.
The rapid assay for deamidated gliadin peptide antibodies was the most sensitive of the point-of-case tests, detecting 63 of 68 previously undiagnosed cases of celiac disease (92.7%; 95% confidence interval, 83%-97.3%), the researchers reported. This sensitivity was very similar to that for standard serology for anti-tissue transglutaminase antibodies (91.2, 95% confidence interval, 81.1%-96.4%), they said. Among the five patients with false-negative results, one was positive for antibodies to both tissue transglutaminase and endomysial antibodies, one was positive only for endomysial antibodies, and three had seronegative celiac disease that was confirmed by a compatible human leukocyte antigen genotype. Notably, four of the five cases that the deamidated gliadin peptide antibody test failed to detect had symptoms such as weight loss, chronic diarrhea, and anemia, meaning that they would have been very likely to be detected by an algorithm that incorporated both rapid assay results and clinical findings, the investigators emphasized.
The deamidated gliadin peptide antibody assay costs about $28 per test and is not yet available in the United States, said the researchers. Using the rapid assay as a point-of-care diagnostic test for celiac disease would save about $9,500 per 1,000 endoscopies, but would miss about 7% of cases, they added. “The prevalence of celiac disease in our cohort was 13%, and represents referral bias to a tertiary celiac center,” they said. “In lower-prevalence populations, such as the 2% of 4% expected for all-comers to endoscopy, the positive predictive value inevitably will decrease and this will have an impact on cost savings.” But negative predictive value also would improve when testing lower-prevalence populations, and negative predictive value is crucial when screening in order to avoid missing true cases of the disease, they emphasized.
Tillotts Pharma makes the deamidated gliadin peptide antibody test and funded the study. One coauthor reported having received relevant research support from Tillotts Pharma, BHR Pharmaceuticals, and Coeliac UK. The other investigators reported having no conflicts of interest.