Looking for Celiac Disease: Diagnostic Accuracy of 2 Commercial Assays

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Looking for Celiac Disease: Diagnostic Accuracy of 2 Commercial Assays
Background: Early diagnosis and treatment with gluten-free diet reduces mortality and the prevalence of associated disorders in celiac disease (CD). A simple "in the office" test of anti-transglutaminase antibodies might be of great help in first-line screening for CD.
Aims: We evaluated the sensitivity and specificity of two commercial kits based, respectively, on rapid detection of IgA-IgG anti-human-transglutaminase antibodies (anti-h-tTG) in serum and IgA anti-h-tTG antibody in one drop of whole blood. These assays were compared to a well-established enzyme-linked immunosorbent assay technique.
Methods: Serum samples were analyzed from 114 biopsy-confirmed celiacs, 120 healthy controls, 20 first-degree relatives of celiacs, and 75 diseased controls. The whole blood samples were analyzed from 51 biopsy-confirmed celiacs and 100 controls.
Results: The serum-based test was positive in all 114 celiacs (sensitivity 100%). Among the controls there were seven healthy blood donors, one first-degree relative, and three diseased controls who tested positive (specificity 94.9%). The blood drop-based assay testing IgA antibodies was positive in 46 of 51 (sensitivity 90.2%), and since three of the five patients testing negative had total IgA deficiency, the sensitivity value can be increased to 95.8%. All 100 controls tested negative (specificity 100%).
Conclusions: The commercial kits described here produce high values of sensitivity and specificity, offering the general practitioner who suspects a possible case of CD the real possibility to look for anti-h-tTG antibodies in his own medical office during a standard visit at a satisfyingly low cost.

Celiac disease (CD) is a gluten-dependent autoimmune disease, estimated to occur in 1% of the population. In pediatric and adult case-finding studies, general physicians have found that the prevalence of CD increases to 12–23% among patients with anemia, to 9% among children with Down syndrome, to 7% among first-degree relatives of CD patients, to 7.6% with isolate stature growth defect, to 5% among patients with autoimmune diseases, and to 1.8% among patients suffering from chronic fatigue. The later the diagnosis of CD, the more likelihood of serious illness and excess mortality. Early diagnosis and treatment with gluten-free diet, on the other hand, reduces mortality and the prevalence of CD-associated disorders. Although definitive diagnosis of CD is still based on certain characteristic histological changes in the jejunal intestine, serological tests for CD screening based on detection of anti-human-transglutaminase antibodies (anti-h-tTG) are cheaper and less invasive, with excellent sensitivity (98%) and specificity (95%). Given the high prevalence of the disease and the implications of missing it (or detecting it late), two prototypes of simple immunoassays were developed as a first step toward speeding up CD diagnosis in the physician's office. Here we present two commercial test kits, based, respectively, on detection of IgA-IgG anti-h-tTG antibodies in serum (Stick CD1, Operon S.A., Saragoza, Spain) and IgA anti-h-tTG antibodies in one drop of whole blood (Biocardâ„¢ Celiac Disease Stick, Ani Biotech Oy, Vantaa, Finland), both performable in 5 min. We prospectively evaluated the sensitivity and specificity of these assays, and interobserver variability in the interpretation of results compared with a well-established enzyme-linked immunosorbent assay (ELISA) technique for the diagnosis of CD.

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