Diagnostic accuracy of a new point-of-care screening assay for celiac disease

AIM: To determine the diagnostic accuracy of a new point-of-care assay detecting anti-deamidated gliadin peptides in celiac disease(CD) patients.METHODS: One-hundred-and-twelve patients(age range: 1.8-79.2 years old) with clinical symptoms suggestive of CD and/or first-degree relatives(FDR) of CD patients(n = 66),and confirmed CD on a gluten-free diet(GFD)(n = 46),were prospectively enrolled in the study at Gastroenterology outpatient clinics for adult patients and from the Gastroenterology Consultation Ward at the Pediatric Department of the University Hospital of Geneva.Written informed consent was obtained from all subjects enrolled.The study received approval from the local ethics committee.The original CD diagnosis had been based on serum-positive IgA anti-tissue transglutaminase enzyme-linked immunosorbent assay(ELISA)(QuantaLite,Inova Diagnostics,San Diego,CA,United States) and on biopsy results.Serum samples from all study participants were tested by the new CD lateral flow immunochromatographic assay(CD-LFIA) device,Simtomax Blood Drop(Augurix SA,BioArk,Monthey,Switzerland) to detect immunoglobulin(Ig)A and IgG antibodies against deamidated gliadin peptides.The diagnostic performance was evaluated using receiver operating characteristic curves with 95%CIs.A cut-off of 2 on the Rann colorimetric scale was used to calculate the device's sensitivity and specificity.RESULTS: CD-LFIA was highly accurate in detecting untreated celiac patients.In the group of patients with CD symptoms and/or FDR,eight new cases of CD were detected by ELISA and biopsy.All of these new cases were also correctly identified by CD-LFIA.The test yielded four false positive and four false negative results.The false positive results were all within the groups with clinical symptoms suggestive of CD and/or FDR,whereas the false negative results were all within the GFD group.The test yeld a sensitivity of 78.9%(95%CI: 54.4-93.9) and specificity of 95.7%(95%CI: 89.4-98.8),and the area under the curve reached 0.893(95%CI: 0.798-0.988).The Kappa coefficient,calculated according to the values obtained by two readers from the same device,was of 0.96(SE: 0.06).When the GFD patients were excluded from the analysis,the area under the curve reached 0.989(95%CI: 0.971-1.000) and the Kappa coefficient,calculated according to the values obtained by two readers from the same device,became 0.96(SE: 0.07).Furthermore,using the Rann scale cut-off of 2 without the GFD patients,sensitivity was 100% and specificity was 93.1%(95%CI: 83.3-98.1).CONCLUSION: The new CD-LFIA rapid screening test shows good diagnostic accuracy,sensitivity and specificity,and may rule out CD in patients with CD-related symptoms.

Clinical utility of quantitative multi-antibody Polycheck immunoassays in the diagnosis of coeliac disease

AIM:To evaluate the clinical utility of multi-antibody strategies in the diagnosis of coeliac disease(CD),the new quantitative Polycheck immunoassays were analysed.METHODS:Polycheck Celiac Panels(PCPs)are immunoenzyme screening assays for the quantitative measurement of coeliac-specific immunoglobulin class G(Ig G)or class A(Ig A)in serum.Lines of relevant antigens are coated together with five Ig G or Ig A standard lines used for the standard curve as positive control.PCP IgA consists of human recombinant human tissue transglutaminase(t TG)and deamidated gliadin peptides(DGP)as targets to detect Ig A antibodies.PCP IgG consists of t TG,DGP and IF(intrinsic factor)antigens to detect antibodies in Ig G class.PCPs were performed on 50 CD patients,including 6 cases with selective Ig A deficiency,and 50 non-coeliac controls.CD diagnosis was performed according to the ESPGHAN recommendations:The presence of specific anti-t TG-Ig A or anti-DGP-Ig G(in the case of Ig A deficiency)antibodies,typical histopathological changes in duodenal mucosa described in Marsh-Oberhüber classification as at least grade 2.The diagnosis of the majority of the control subjects was functional gastrointestinal disorders.The PCP results were compared with reference EliA Celikey.RESULTS:The usage of PCPs led to the correct identification of all CD patients.In our study,PCPs showed 100%agreement with the histopathological results.PCP IgA test showed a 98%concordance and correlated positively(R=0.651,P=0.0014)with Eli A Celikey test.The highest specificity and positive predictive value(both 100%)were observed for the detection of Polycheck anti-t TG-Ig A antibodies.The highest sensitivity and negative predictive value(both 100%)were achieved by Polycheck anti-DGPIg G antibody detection.The best performance(98%sensitivity and negative predictive value,100%specificity and positive predictive value,diagnostic accuracy-AU ROC 99%)was observed for the strategy of using both PCP IgA and IgG and determining positive outcomes of the test with two or more coeliac-specific antibodies detected.The majority of coeliac patients had multiple antibodies.All four antibodies were detected in 7(14%)cases,19 children(38%)were positive for three antibodies and 23(46%)were positive for two antibodies.CONCLUSION:The present study showed that detection of coeliac-specific antibodies with multi-antibody PCPs is effective and efficacious in the diagnosis of CD.

Effect of succinic acid deamidation-induced modification on wheat gluten

The effect of succinic acid deamidationinduced modification on wheat gluten was investigated in the present study.The changes of surface hydrophobicity,functional properties,secondary structure,and sensibility of proteolysis of modified samples were determined.The solubility of deamidated proteins increased in the isoelectric region of untreated wheat gluten.The isoelectric point of succinic acid deamidated wheat gluten was shifted to a basic pH and existed in the broad pH regions.Foaming property and molecular flexibility of wheat gluten were improved after the modification.The hydrolysis degree of the hydrolysates in proteolysis with flavorzyme and pancreatin increased after succinic acid deamidation.Moreover,succinic acid deamidation-induced modification resulted in little change in molecular weight and secondary structure of the protein.Thus,succinic acid could facilitate unfolding protein conformation.In addition,it could improve protein-water interactions,surface properties,and sensibility of the proteolysis of the deamidated wheat gluten.