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Diagnostic Testing Algorithms for Celiac Disease


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Algorithm Breakdown

Slide 13

updated June 2011

The Comprehensive Cascade begins with both total IgA and HLA-DQ typing.  All further testing reflexes automatically within the lab based on the IgA result. This reflexing occurs regardless of the HLA result.

The IgA result is classified as normal, or within the age-adjusted reference range, as low, being still detectable but below the reference range, or as deficient, or undetectable by our nephelometric assay.

All samples with a normal IgA result would automatically reflex to a TTG-IgA antibody.

For all samples testing positive or negative, no further testing would be required. The final report would include the total IgA, TTG-IgA antibody, and HLA results, along with an interpretive comment. However if the TTG-IgA result falls into the equivocal range, then EMA and deamidated gliadin-IgA testing is performed. These results, along with the total IgA, TTG-IgA, and HLA typing results, would be included in the final report.

On the other side of the cascade, those individuals who have no detectable IgA or have a selective IgA deficiency would have TTG and deamidated gliadin testing performed, but only the IgG isotypes. These results would be released as part of the final report.

Finally, for those individuals with low but detectable IgA  TTG and deamidated gliadin, both IgA and IgG isotypes, would be performed. Again, all those serologic results, along with the HLA typing would be included in the final report.

This cascade is designed to perform all testing necessary to identify patients who may have celiac disease and in whom a biopsy would be suggested.  It is not applicable to patients who have been following a gluten-free diet or who have been previously typed for the celiac-associated HLA-DQ alleles.  For individuals who are already known to be DQ2 or DQ8 positive, or for individuals who do not want the HLA typing performed, the serologic cascade may be an option.

Algorithm Breakdown


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