What is the workup for a patient who experiences diarrhea after consuming wheat or eggs?

Diagnostic Workup for Wheat and Egg-Related Diarrhea

The appropriate workup for a patient experiencing diarrhea after consuming wheat or eggs should include testing for food allergies, celiac disease, and eosinophilic esophagitis, with food elimination and challenge testing being the gold standard for diagnosis.

Initial Assessment

History Elements to Focus On

• Timing of symptoms in relation to food consumption
• Consistency and frequency of diarrhea
• Associated symptoms (abdominal pain, bloating, nausea)
• Other foods that may trigger symptoms
• Family history of food allergies or celiac disease
• History of atopic conditions (eczema, asthma, allergic rhinitis)

Laboratory Testing

1. Celiac disease screening:

   • Tissue transglutaminase antibodies (tTG-IgA)
   • Total IgA level (to rule out IgA deficiency)
   • Consider deamidated gliadin peptide antibodies (DGP IgG) if IgA deficient 1

2. Food allergy testing:

   • Food-specific IgE testing for wheat and egg
   • Skin prick testing for immediate hypersensitivity reactions
   • Consider patch testing for non-IgE mediated reactions 2

3. Additional tests:

   • Complete blood count with differential (to assess for eosinophilia)
   • Stool studies to rule out infectious causes
   • Fecal calprotectin (to assess for inflammatory bowel disease)

Diagnostic Algorithm

Step 1: Rule Out Celiac Disease

Celiac disease must be ruled out before initiating any elimination diet, as patients need to be consuming gluten for accurate testing 3.

Step 2: Consider Food Allergy Types

Determine if symptoms suggest:

• IgE-mediated allergy (rapid onset, potential anaphylaxis)
• Non-IgE mediated allergy (delayed symptoms, primarily GI manifestations)
• Mixed IgE/non-IgE reactions (as seen in eosinophilic esophagitis) 2

Step 3: Elimination Diet and Challenge Testing

The gold standard for diagnosing food allergies is elimination followed by controlled challenge:

1. Elimination phase:

   • Remove suspected trigger foods (wheat and eggs) for 2-4 weeks
   • Monitor for symptom improvement
   • Consider dietitian support to ensure nutritional adequacy 1

2. Challenge phase:

   • Reintroduce one food at a time under medical supervision
   • Start with low doses and gradually increase
   • Monitor for return of symptoms
   • Document timing and nature of reactions 4

For suspected eosinophilic esophagitis, endoscopy with biopsy may be required during both elimination and challenge phases to assess histological response 1.

Special Considerations

Non-Celiac Wheat Sensitivity

If celiac testing is negative but symptoms persist with wheat consumption, consider non-celiac wheat sensitivity (NCWS) 3. This diagnosis is made by exclusion after ruling out celiac disease and wheat allergy.

Exercise-Induced Wheat Allergy

Some patients may experience symptoms only when wheat consumption is followed by exercise. This can mask the connection between wheat and symptoms 5.

Food Intolerance vs. Allergy

Distinguish between true food allergies (immune-mediated) and food intolerances (non-immune mechanisms):

• Lactose intolerance may coexist and complicate the picture
• FODMAPs in wheat may cause symptoms independent of gluten or wheat proteins 3

Management Approach

Based on diagnostic findings, management may include:

1. For confirmed food allergies:

   • Complete elimination of trigger foods
   • Education on hidden sources of allergens
   • Emergency action plan if IgE-mediated 1

2. For eosinophilic esophagitis:

   • Targeted elimination diet based on identified triggers
   • Step-up approach starting with 2 food elimination (milk +/- wheat or egg)
   • Consider endoscopic monitoring of response 1

3. For non-celiac wheat sensitivity:

   • Gluten/wheat restriction with periodic reassessment
   • Consider low-FODMAP diet trial if symptoms persist 3

Common Pitfalls to Avoid

1. Premature dietary restriction: Don't recommend elimination diets before proper testing for celiac disease, as this can lead to false-negative results.

2. Assuming cross-reactivity: Clinical cross-reactivity with other foods in the same group is unpredictable 2.

3. Overlooking mixed mechanisms: Some patients may have both IgE and non-IgE mediated components to their food allergy 2.

4. Inadequate follow-up: Regular reassessment is needed, as food allergies and sensitivities can change over time, particularly in children 1.

5. Missing infectious causes: Always consider infectious etiologies of diarrhea before attributing symptoms solely to food allergies 1.

Remember that proper diagnosis is essential to avoid unnecessary dietary restrictions that may impact quality of life and nutritional status.