What should happen at the doctor’s:
Diagnosing CMA will take your child’s doctor a bit more than just doing a single test.Your child’s symptoms, medical history and assessment as well as any test results will be considered when deciding if your child has a food allergy.
How you can best prepare yourself for the visit:
When it comes to diagnosing allergies, the child’s medical history may be as important as any diagnostic test results. Information about your medical family history as well as the medical history of your child should be prepared before visiting the doctor.
Additionally, it’s a good idea to prepare questions you might like to ask your doctor, such as:
Which diagnostic tests might your doctor want to perform:
Your child’s doctor should use all of the information mentioned above to decide whether allergy tests are called for. Allergy testing can involve skin or blood tests as well as diagnostic diets. Which type of test your doctor considers to be suitable depends on the type of allergy suspected.
Skin tests are given preference because they are rather quick. When allergic reactions happen very soon after your child has eaten, a positive skin or blood test is more likely, whereas symptoms that appear only after a while are more difficult to prove in the blood. Please note that these kind of allergy tests are just one part of the diagnosis process as wrong positive or wrong negative results may occur. That means that your child can show allergy symptoms in spite of the test saying he or she is not allergic.
Diagnostic diets such as elimination diets or food challenges might be chosen when allergic reactions happen hours or days after the food is eaten.
All these tests have to be performed under medical supervision by a formally-trained allergist doctor or allergist.
With the information from your child’s medical background, symptoms and allergy testing, you and your child’s doctor will be able to develop a plan to manage the symptoms.
National Institute for Health and Clinical Excellence. 2011
|Skin Prick Tests (SPTs or PSTs)||
Skin Prick Tests are especially accurate in testing cow’s milk allergy. Small drops of cow’s milk or suspected other foods are placed on the child’s forearm. A small prick is made through each drop into the skin. If the child’s skin becomes red and itchy, it usually means that he or she is allergic to that particular allergen. This is called a positive reaction. If no reaction is shown in the test, there is still a chance of your child being food allergic. This can happen if your child shows delayed reactions after food intake, a so called non-IgE reaction.
Skin Prick Tests are rather quick. So they are often used as first tests to assess against which foods antibodies are produced. Once the allergens are identified, the doctor may perform more specific tests (e.g. RAST).
|Atopy Patch Test (APT)||With an Atopy Patch Test (APT) late onset symptoms, especially atopic dermatitis and late abdominal symptoms can be tested. APT has the advantage of being able to prove CMA even when prick tests and blood tests are negative. The allergenic food extract is applied on a pad that is taped to the skin of the child’s back and left there for 24 to 72 hours. The ATP tests the reaction of the so called T-Cell (part of the white blood cells which have an important immunity function).|
|Specific IgE tests (formerly known as RAST test)||Specific IgE tests are blood tests that can measure the concentration of specific antibodies in the child’s blood. These antibodies are called IgE. IgE levels in the blood are often higher in children who have allergies or asthma. If RAST is negative, it is still possible that your child has a food allergy, but in this case it is a non-Ige or delayed reaction.|
|An elimination diet can be recommended by your child’s doctor in order to prove that your child reacts to foods such as cow’s milk, eggs, wheat, or soya. With the results gained from this elimination diet, the medical history of your child, blood tests as well as the food and symptom diary your doctor will have something to work on when trying to reach a diagnosis. How to organise such a diet: under the strict supervision of your child’s doctor or dietitian the food suspected to cause the trouble will be eliminated from your baby’s diet for about one to two weeks. It is important that you avoid all foods that contain the relevant trigger, your child’s doctor or dietitian will give you precise instructions on how to do this. To feed your infant adequately during an elimination diet, a special cow’s milk protein free infant formula such as an amino acid-based formula might be prescribed.|
|Food challenges||Your child’s doctor may want to initiate a food challenge if he thinks it is possible that your child has outgrown his or her food allergy. Before starting it, your child’s symptoms should have disappeared or at least been stabilised. What can you expect? In a challenge test, very small amounts of an allergen are taken by mouth. Foods may be masked in various infant formulas, fruit juices, pureed foods or meat patties depending on the age of the child. Food challenges can be performed open (both your doctor and you know what your child is going to be given), single blind (your doctor knows but you don't) or double-blind placebo-controlled, which means that neither your doctor nor yourself know if the child gets the allergenic formula or a placebo one. The kind of food challenge performed on your child will depend on the practice and methodology commonly applied in the children's clinic and on your child’s doctor.|
Caution! Challenge tests should be supervised by a child’s doctor and dietitian and are best conducted in a clinic or hospital setting with qualified personnel and equipment.