Introduction
The latest European guidelines endorse a no-biopsy approach for diagnosing coeliac disease in selected patients with markedly elevated IgA anti-tissue transglutaminase (tTG) antibody levels, provided that serological results are reliable and meet defined criteria. Nevertheless, the application of this strategy depends on the standardization, accuracy, and consistency of serological assays across laboratories. In this nationwide survey, we therefore aimed to assess the availability and inter-laboratory variability of coeliac disease testing throughout Italy.
Methods
We conducted a comprehensive email and telephone survey of laboratory managers from public hospitals across the Italian national territory, as well as a sample of 18 private centres nationwide. Data collected included assay types, reporting methods, upper limit of normal (ULN) thresholds, turnaround times, total IgA testing, and the availability of anti-endomysial antibodies (EMA), IgG anti-tTG, Deamidated Gliadin Peptide (DPG) IgG and DPG IgA.
Results
A total of 291 public hospitals and 18 private laboratories across Italy were approached, with responses obtained from 19 out of 20 regions. The overall response rate was 48% (n=148). Only 36% of the laboratories routinely measured total IgA when IgA anti-tTG was requested. EMA testing was available in 93% of laboratories, IgG anti-tTG in 85%, DGP IgG in 90%, and DGP IgA in 66%. Among responding sites, 61 performed coeliac serology testing in-house, while 87 referred samples to external laboratories. Among centres performing testing, 11 different IgA anti-tTG assays were identified, with eight different cut-offs used, spanning from 3.5 to 30 IU/mL, even among laboratories using the same assay. The median turnaround time for IgA anti-tTG results was 5 days.
Conclusion
Marked variability in coeliac serology testing across Italian laboratories represents an important challenge for the appropriate and consistent application of the no-biopsy approach in clinical practice. Greater national standardisation of serological assays is needed to support its implementation.