Diagnostic accuracy of a new point-of-care screening assay for celiac disease(1)
The initial diagnosis of CD is made by serological testing and confirmed either by histopathologic examination of small-bowel biopsy or further blood tests, depending on the serum concentration of anti-tissue transglutaminase (tTG) autoantibodies. The detection of antibodies against deamidated gliadin peptides (DGP) has demonstrated very high sensitivity, as well as a diagnostic accuracy that is at least equivalent to the established serological assays.
The device runs with samples representative of the various diagnoses. Each sample was tested by two independent user-operators blinded to the subject’s histories and laboratory findings and each of whom performed the CD-LFIA interpretations twice on two independent devices.
A total of 112 patients (71 females, 36 males; no sex information was available for five patients) with a mean age of 24.6 years old (median 13.9 years; range: 1.8-79.2 years) were analyzed. The CD prevalence in this study was 12.1%. The overall agreement between the CD-LFIA test and the ELISA laboratory test results is shown. CD-LFIA tests showed four false-positive results, all in the FDR and CD symptoms group. All of the ELISA laboratory test results were below the cut-off value and the Rann scores were between 2 and 3, just near the cut-off value. There were also four false-negative results obtained by the CD-LFIA device, all of which were from the CD GFD group. The serological IgA-tTG level of these patients was near the cut-off values.
The AUCs for each CD-LFIA device used and for each user-operator were 0.869 (95%CI: 0.764-0.975) and 0.893 (95%CI: 0.798-0.988), indicating excellent diagnostic performance of the test. Exclusion of the CD GFD patients from the ROC analysis brought the AUC up to 0.989 (95%CI: 0.971-1.000), depending on the device and user-operator.
The results showed that a sensitivity for the CD-LFIA device of 78.9% (95%CI: 54.4-93.9) and a specificity of 95.7% (95%CI: 89.4-98.8), as compared to the serological IgA-tTG levels detected by the ELISA laboratory tests. When the CD GFD patients were excluded and the Rann cut-off of 2 was used, the sensitivity was 100% (95%CI: 63.1-100) and the specificity remained nearly unchanged at 93.1% (95%CI: 83.3-98.1) (Table 1). The LR+ became 14.5 (95%CI: 5.8-49.0) and the LR- became 0.00 (95%CI: 0.00-0.39), respectively.
Besides the improved detection methods, other etiological factors appear to have contributed to the increased prevalence, and, similar to other autoimmune conditions, these may include different environmental factors, such as gluten, antigens in breast milk, or from other pathogenic infections. The device has a good discriminative ability between patients with CD and those without CD.