Antibodies to gliadin (wheat protein) have been shown conclusively to be the toxic agent in celiac disease. Originally, a series of multiple intestinal biopsies was required to diagnose celiac and related intestinal diseases. More recently, serologic testing has been strongly suggested for screening patients with suspected gluten-sensitive enteropathy as well as for monitoring dietary compliance. Celiac disease usually begins in infancy soon after introduction of cereals to the diet, but symptoms may disappear spontaneously in later childhood despite continued signs of malabsorption. Strict avoidance of gluten in the diet is recommended to control the disease.
Both IgG and IgA gliadin antibodies are detected in sera of patients with gluten-sensitive enteropathy. IgG antigliadin antibodies seem more sensitive but are less specific than the IgA class antibodies. The best strategy for at-risk populations includes testing for both classes of gliadin antibodies.
Values are given for >2 years of age and are for IgA or IgG.
Negative: <25 U/mL by ELISA
Weakly positive: 25–50 U/mL
Positive: >50 U/mL
Collect a 7-mL blood serum sample in a red-topped tube. Observe standard precautions.
Label the specimen with the patient’s name, date, and test(s) ordered and place in a biohazard bag for transport to the laboratory.
The gliadin antibody assay has a sensitivity of 95% for active, untreated celiac disease when both IgG and IgA are used. The test has an overall specificity of 90%.
A negative IgA result in an untreated patient does not rule out gluten-sensitive enteropathy, especially when associated with elevated levels of IgG gliadin antibodies.
Significant numbers of celiac patients are IgA deficient, which can serve as an explanation for this occurrence.
In treated patients known to express IgA antibodies, the IgA gliadin antibody level represents a better indicator of dietary compliance than the IgG level.
False-positive results (high antibody levels without the corresponding histologic features) are possible; other gastrointestinal disorders, especially Crohn disease, postinfection malabsorption, and food protein intolerance (e.g., cow’s milk), are known to induce circulating antigliadin antibodies.
Results of this assay should be used in conjunction with clinical findings and other serologic tests.
Pretest Patient Care
Explain test purpose and procedure.
Follow guidelines in Chapter 1 for safe, effective informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan if needed based on the test results in light of the patient’s dietary history, including related clinical, laboratory, and histologic data. Positive results are possible in patients with other gastrointestinal disorders.
A biopsy of the proximal small bowel is recommended if the test is positive.
Often, a diagnosis provides some relief since the patient has been experiencing symptoms for many years and now can be treated appropriately.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.