Other Tests
Soy-induced GI symptoms are not usually immunoglobulin E (IgE)-mediated; therefore, both skin tests and determination of specific IgE in serum have a low diagnostic value.
Radioallergosorbent assay test (RAST) appears to be of poor predictive value. Many children with positive results do not react to challenge tests.
Prick tests have little predictive value. The acidic subunits of glycinin and beta-conglycinin appear to be present in reduced amounts or absent in some commercial soybean skin test extracts tested by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. As a consequence, these commercial extracts are less sensitive than extracts of soy flour.
Patch testing may provide more clinical relevant informations, particularly in children with eczema.
The role of atopy patch test in children with food allergies (including to soy) presenting with constipation has also been suggested. [21]
The challenge test with soy proteins, after an elimination diet, is the only reliable method of evaluating soy protein intolerance.
Procedures
Endoscopy
During the workup for differential diagnoses, upper or lower GI endoscopies are often performed in patients with soy protein intolerance. However, findings are nonspecific, most commonly minimal, and, at times, even completely unremarkable. Accordingly, and because of the transient nature of the disorder, endoscopies are not considered essential.
Esophagogastroduodenoscopy
Macroscopically, only minimal erythematous changes may be observed.
Microscopically, any area (eg, lower esophagus, gastric body, antrum, duodenum) may or may not show signs of acute inflammation.
In a minority of patients, an infiltrate of eosinophils is observed.
When the clinical presentation is that of a malabsorption syndrome, the duodenal mucosa may have changes (eg, partial villous atrophy, crypt hyperplasia) indistinguishable from those of celiac disease.
Colonoscopy
Macroscopically, changes may vary from minimal erythematous segments, most commonly diffusely involving the distal colon, to severe inflammation with bleeding ulcers and loss of vascular markings.
Microscopically, nonspecific acute inflammatory changes are observed, typically indistinguishable from infectious colitis. Rarely, eosinophils predominate in the lamina propria.
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Typical atopic dermatitis on the face of an infant.
