Diagnosis of Cow Milk Protein Allergy − Current Methods and Their Diagnostic Value
Cow milk protein allergy (CMPA) is among the most common pediatric food allergies. In case of early reaction, the child should be immediately referred to an allergist; for delayed symptoms, an elimination-exposure test can be performed under the guidance of a pediatrician.
Diagnostic Options for CMPA
The initial diagnosis of cow milk protein allergy typically relies on a precise medical history. In cases of early reaction, where CMPA symptoms appear within 2 hours of ingesting cow milk, the child should be immediately referred to an allergist. For delayed symptoms that occur 2 hours to 3 days after consuming cow milk, an elimination-exposure test can be carried out under the supervision of a pediatrician. Children with early symptoms of CMPA, which commonly involve IgE reactions, experience respiratory, skin, and gastrointestinal issues. Delayed symptoms of CMPA (generally non-IgE mediated reactions) usually manifest as skin problems such as eczema, gastrointestinal issues, and general symptoms like food refusal or failure to thrive.
Importance of Suitable Infant Nutrition
In addition to early diagnosis, providing appropriate infant nutrition is crucial for children with CMPA to quickly and effectively relieve allergy symptoms. An extensively hydrolyzed infant formula based on casein with the probiotic strain Lactobacillus rhamnosus GG (LGG) and a unique peptide profile is a suitable choice. This formula is observed to relieve infantile colic in 90% of infants, reduce atopic dermatitis symptoms, and eliminate traces of blood from stool within 4 weeks.
Elimination-Exposure Test
The diagnostic elimination-exposure test involves withdrawing milk or regular milk-based infant formula and adhering to a dairy-free diet. Milk can be replaced with either extensively hydrolyzed milk protein (eHF), which does not induce allergic reactions, or amino acid formulas (AAF) that do not contain even residual amounts of milk protein.
If CMPA occurs in breastfed children, it is essential to strictly eliminate milk and dairy products from the mother's diet. Reexposure to cow milk should occur again through breast milk. The recommended duration for the elimination diet is 4 weeks. During this period, children with CMPA should experience a significant reduction in cow milk protein allergy symptoms. Upon reintroducing milk or milk-based infant formula into the child's diet, the original issues should reappear.
Procedure in the Allergist's Office
Allergist-led diagnosis of CMPA involves a blood test to determine IgE antibodies against cow milk, known as sIgE. The positivity threshold is set at 0.35 kU/l. Higher values increase the likelihood of a CMPA diagnosis. Measuring sIgE levels is significant in IgE-mediated reactions as it helps monitor the patient’s progress. The speed of developing tolerance to cow milk can be predicted based on sIgE dynamics. Determining other antibodies besides sIgE is currently not recommended because IgG or IgA antibodies against milk are not diagnostically valuable for CMPA.
The allergist should also conduct skin prick tests, applying milk to the skin and penetrating the outer layer. The reaction is read after 15 minutes, with a positivity threshold set at 3 mm for the resulting wheal. Another potential diagnostic method for CMPA is the atopy patch test, where the reaction to a patch with milk in a test chamber applied for 48 hours on the back is observed. However, these tests are not available at all allergist facilities and have low sensitivity.
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Sources:
1. Nutramigen LGG – Much More than Allergy Symptom Relief. Ewopharma, 2018.
2. Bělohlávková S. Cow Milk Protein Allergy – Diagnosis. Ewopharma, 2018.
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