Elevated Poster Presentation International Celiac Disease Symposium 2026

Feasibility and Diagnostic Performance of a Needle-Free Salivary ADAP Assay for Coeliac Disease Screening (147012)

Cynthia Kanagasundaram 1 , Madeleine Cumming 2 , Dexing Huang 1 , Nazli Somuncuoglu 3 , Amy Russell 3 , Olivia Moscatelli 2 , Joanna Efklides 4 , Alice Becker-Scott 1 , Jesse Ekin 1 , Melinda Hardy 2 , John M. Wentworth 5 , Jason A. Tye-Din 2
  1. Department of Gastroenterology, Royal Melbourne Hospital, Parkville, Victoria, Australia
  2. Immunology Division, The Walter and Eliza Hall Institute, Parkville, VIC, Australia
  3. Walter and Eliza Hall Institute, Parkville, VIC, Australia
  4. Alfred Hospital, Melbourne
  5. Department of Diabetes and Endocrinology, The Royal Melbourne Hospital, Parkville

Introduction: Serum tTG-IgA is the first-line test for coeliac disease (CeD), but symptom-based, clinician-initiated testing detects only a minority of cases. Interest in population-based screening is therefore growing, creating a need for scalable, non-invasive tests. Saliva testing is attractive, although antibody detection has historically been limited by low analyte abundance. We evaluated whether an ultrasensitive antibody-dependent agglutination PCR assay could detect salivary tTG-IgA and identify active CeD in adults.

 

Methods: Unstimulated saliva and matched serum were collected from adults with biopsy-proven CeD, including newly diagnosed active CeD and treated CeD on a gluten-free diet, and from healthy controls. Salivary and serum tTG-IgA were measured using the ADAP assay, which detects antibody-mediated agglutination of tTG-DNA conjugates by PCR. Serum was also assessed using standard chemiluminescent immunoassay (CLIA; Inova QUANTA Flash). Diagnostic accuracy for active CeD was evaluated by ROC analysis. The impact of saliva collection method and 48-hour room-temperature storage, simulating postal transport, was assessed.

 

Results: The cohort included 43 adults (19 active CeD, 12 treated CeD, 12 healthy controls). All active CeD participants were serum tTG-IgA-positive by standard serology. Treated participants had followed a gluten-free diet for a mean of 7.6 years; 10/12 were tTG-IgA-negative. For distinguishing active CeD from treated CeD and controls, salivary ADAP showed 95% sensitivity, 100% specificity, and an AUROC of 0.98. Salivary ADAP correlated strongly with serum ADAP, r=0.72, p<0.0001, while serum CLIA and serum ADAP showed moderate correlation, r=0.46, p=0.0081. Passive drool collected via funnel produced a median 1.96-fold higher salivary tTG-IgA level than absorbent cotton swab-based Salivette collection. Salivary tTG-IgA remained stable after 48-hour room-temperature storage.

 

Conclusions: Salivary tTG-IgA was detectable in active CeD using an ultrasensitive ADAP assay and showed high diagnostic accuracy. Passive collection improved tTG-IgA yield, and room-temperature stability supports remote, at-home sample collection. Larger validation studies are underway.