Coeliac Disease Case Finding and Diet Monitoring by Point-of-Care Testing

I.R. Korponay-Szabó; T. Raivio; K. Laurila; J. Opre; R. Király; J.B. Kovács; K. Kaukinen; L. Fésüs; M. Mäki

Disclosures

Aliment Pharmacol Ther. 2005;22(8):729-737. 

In This Article

Summary and Introduction

Background: Immunoglobulin A class transglutaminase autoantibodies are highly predictive markers of active coeliac disease, a disorder difficult to recognize solely on clinical grounds.
Aims: To develop and evaluate a simple rapid test for point-of-care detection of coeliac autoantibodies.
Methods: The novel whole blood test utilizes the patient's endogenous transglutaminase in red blood cells for detection of transglutaminase-specific immunoglobulin A antibodies present in the blood sample, with normal plasma immunoglobulin A detection as positive test control. We evaluated 284 patients under suspicion of coeliac disease and undergoing jejunal biopsy, and 263 coeliac patients on a gluten-free diet, 383 being tested prospectively in a point-of-care setting. Results were compared with histology, conventional serum autoantibody results and dietary adherence.
Results: The rapid test showed 97% sensitivity and 97% specificity for untreated coeliac disease, and identified all immunoglobulin A-deficient samples. Point-of-care testing found new coeliac cases as efficiently as antibody tests in laboratory. Coeliac autoantibodies were detected onsite in 21% of treated patients, while endomysial and transglutaminase antibodies were positive in 20% and 19%, respectively. The positivity rate correlated with dietary lapses and decreased on intensified dietary advice given upon positive point-of-care test results.
Conclusions: Point-of-care testing was accurate in finding new coeliac cases and helped to identify and decrease dietary non-compliance.

Coeliac disease is an autoimmune gastrointestinal disorder induced by ingestion of gluten found in wheat, rye and barley.[1,2] The active disease is characterized by gluten-dependent autoantibodies against endomysium (EMA), a complex connective tissue structure surrounding smooth muscle cells, and more precisely, against the protein type 2 ('tissue') transglutaminase (TG2), the coeliac autoantigen anchored to endomysial collagen by fibronectin.[3,4] Detection of these autoantibodies in the serum is a useful means of identifying new coeliac patients presenting with only mild gastrointestinal symptoms, non-specific general complaints or extraintestinal manifestations, or in populations in general.[1,5,6,7,8] A further important application of serological tests is the regular monitoring of dietary adherence in treated patients, as the autoantibodies disappear from the serum on a strict gluten-free diet.[9] There is thus call for quick, easy-to-perform, economical and widely accessible coeliac antibody tests which can be carried out at the first care-taking level locally.

Currently, coeliac-specific serum antibody tests are centralized in specialized laboratories to ensure appropriate sensitivity and specificity.[9] Testing is costly and the turnaround time of results may be relatively long.

Natural human TG2 protein is also found within the red blood cells,[10] and thus in any diagnostic blood specimens comprising whole blood. This easily available endogenous TG2 antigen has, after liberation by haemolysis, the potential to bind to and thereby detect coeliac autoantibodies present in the same sample without need for purified, external TG2 antigen,[11] serum separation, and possibly even without a laboratory reader. This innovative means of detection thus offers an opportunity for point-of-care testing (POCT), defined as performing a diagnostic procedure in a variety of environments outside the central laboratory.[12]

In the present study, we showed a simple self-TG2-based rapid whole blood test to be accurate in detecting untreated coeliac disease. The performance of the test was further evaluated in point-of-care (POC) settings in finding new cases and monitoring treatment.

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