Diagnostic accuracy of a novel point-of-care test for simultaneous detection of anti-transglutaminase IgA and anti-deamidated gliadin IgG antibodies

Abstract

Background: Point-of-care tests (POCTs) may have a role in detecting undiagnosed cases of Celiac disease (CD). We assessed the diagnostic accuracy of a novel POCT, compared with the conventional serological methods, for simultaneous anti-transglutaminase (tTG) IgA and anti-deamidated gliadin (DGP) IgG antibody detection. Furthermore, we evaluated the effect of different biological matrices (whole blood and serum) on test performance.

Methods: Serum and whole blood from celiac or suspected celiac patients who underwent duodenal biopsy were assayed for the presence of anti-tTG IgA and anti-DGP IgG both with the reference standard methods (Thermo Fisher Scientific, Uppsala, Sweden) and with the POCT (PRIMA Lab SA, Balerna, Switzerland).

Results: 266 sera (101 negative and 165 positive) and 60 whole blood samples (34 positive and 26 negative) were included in the study. POCT for anti-DGP IgG showed a sensitivity of 84.3% and a specificity of 90.1%, with positive (PPV) and negative predictive values (NPV) of 91.07% and 82.73%. POCT for anti-tTG IgA showed a sensitivity of 98.31% and a specificity of 98.02%, with a PPV and NPV of 98.31% and 98.02%. Test accuracies were 86.94% and 98.17%, respectively. The agreement of the results between the two different matrices showed a strong correlation rate: 95% for anti-DGP IgG and 100% for anti-tTG IgA.

Conclusion: The anti-tTG IgA/anti-DGP IgG-based POCT showed good diagnostic accuracy with comparable sensitivities and specificities to reference standard methods in detecting CD in symptomatic patients and could be considered as a mass screening test before referring to conventional serology.

Keywords: anti-deamidated gliadin antibodies; anti-transglutaminase antibodies; case-finding test; celiac disease; early diagnosis; lateral-flow immunochromatography assays; point-of-care testing; screening test.

FIGURE 1

Design of the study and recruitment of patient samples. CD: Celiac disease; FI: fluoroenzyme immunoassays; DB: duodenal biopsy; anti‐DGP IgG: anti‐deamidated gliadin Immunoglobulin G; anti‐tTG IgA: anti‐tissue transglutaminase Immunoglobulin A.

FIGURE 2

Schematic representation of test structure. From left to right the three test lines: the anti‐DGP IgG (T1 line), the anti‐tTG IgA (T2 line) and the control line (C line).

FIGURE 3

Schematic representation of the possible results obtained with the POCT for the simultaneous detection of anti‐DGP IgG and anti‐tTG IgA. Anti‐DGP IgG: anti‐deamidated gliadin Immunoglobulin G; anti‐tTG IgA: anti‐tissue transglutaminase Immunoglobulin A.