Change to Pathlab Coeliac Disease Algorithm – No upfront total IgA testing
Pathlab utilises anti-tTG IgA as the primary screening test for coeliac disease. This is traditionally accompanied by a total IgA test to confirm the patient is not IgA-deficient (IgA undetectable, <0.05 g/L) as this causes false negative anti-tTG results. Anti-DGP IgG is automatically added by the laboratory when total IgA is found to be <0.05 g/L, this is a more reliable test in the absence of IgA.
We have evaluated a more efficient alternative to testing total IgA on all samples which reliably indicates IgA-deficiency. This means the total IgA level will only be tested on those samples suspected of being IgA-deficient. This algorithm is already in place in Canterbury Health Laboratories and follows published studies.
Our extensive evaluation has confirmed the appropriateness of such a strategy.
From November 11th 2025 Pathlab will cease initial total IgA testing on all coeliac requests. Total IgA will be added selectively by the laboratory based on the initial anti-tTG IgA result. The result used to make this decision will not be reported. Anti-DGP IgG will continue to be added automatically if the IgA result is <0.05 g/L.