Effective Tuesday, December 17, 2013, the University of Iowa Hospitals and Clinics core clinical chemistry laboratory will institute new assays for the celiac disease-related antibodies.  The two new offerings will be tissue transglutaminase IgA and gliadin (deamidated) IgA antibodies.

IgA antibodies are preferred for tissue transglutaminase and deamidated gliadin antibodies.  The IgG antibodies for these markers have lower sensitivity for celiac disease.  However, tissue transglutaminase and deamidated gliadin IgA antibodies are not reliable in the setting of total IgA deficiency.

The new tests include an automatic determination for whether the total IgA levels are sufficient for measurement of celiac-related IgA antibodies.  If the total IgA level is too low, the IgA testing is cancelled (in Epic will read “LOW IGA” as result) and there is automatic reflex to tissue transglutaminase IgG or gliadin (deamidated) IgG antibodies.  There is no need to separately order total IgA (which will carry additional patient charges) unless there are other clinical reasons for doing so.

Test availability is 24 hours/day, 7 days a week (including holidays), with turn-around time of 2 hours or less upon receipt in the laboratory.  Other details on the tests are as follows:

Test name	Epic #	Specimen*	Reference range (U/mL)
TISSUE TRANSGLUTAMINASE IGA	LAB8013	Red top tube	Neg: < 15 Positive: 15 or greater
TISSUE TRANSGLUTAMINASE IGG	LAB8014	Not directly orderable; performed as reflex if TTG IgA cannot be done due to low total IgA level	Neg: < 15 Positive: 15 or greater
GLIADIN (DEAMIDATED) IGA ANTIBODY	LAB8011	Red top tube	Neg: < 15 Positive: 15 or greater
GLIADIN (DEAMIDATED) IGG ANTIBODY	LAB8012	Not directly orderable; performed as reflex if gliadin IgA cannot be done due to low total IgA level	Neg: < 15 Positive: 15 or greater

*3 mL whole blood or two pediatric microtainers

These changes do not impact ENDOMYSIAL ANTIBODY-IGA (LAB1301) or ENDOMYSIAL ANTIBODY-IGG (LAB1305) performed by indirect immunofluorescence.  These will continue to be offered.

Questions should be directed to Matthew Krasowski, MD, PhD, medical director of the Clinical Chemistry Laboratory (384-9380, matthew-krasowski@uiowa.edu).