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Oral Food Challenge

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Oral Food Challenge

Adult OFC for FPIES

The oral food challenge (OFC) is performed to assess resolution of FPIES. It is important to have a shared decision-making process on proceeding with the OFC. It should be discussed with the patient that depending on the severity of the past FPIES reaction, it may be necessary to place a peripheral IV prior to starting the oral food challenge. Additionally, emergency medication will need to be available and placed at the bedside prior to starting the challenge. The medications may include normal saline (IV 20mg/kg), ondansetron (PO, IV, IM 0.15mg/kg/dose; max dose of 16mg/dose) and methylprednisone (IV 1mg/kg). Prior to scheduling the OFC, the patient will be counseled on the duration of the OFC as well as the form and amount of food that will be administered.

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Prior to OFC a patient will need to be assessed for the presence of food specific IgE via skin prick testing with commercial extract or fresh food or serum blood ImmunoCAP immunoassay to assess atypical FPIES and the challenge protocol that should be considered based on the presence or absence of IgE

On the day of the challenge, the patient will be required to be in their baseline state of health and with no presenting illness. Current guidelines proposed in the OFC consensus guidelines (Bird et al 2020) have recommended that an FPIES OFC should be measured by 0.06-0.6 grams of protein per kilogram of body weight. The dose is then maxed out at 3 grams of food protein. This of course has been suggested in pediatric patients. For the adult OFC, Gonzalez et al (JACI Pract 2022) recommend calculating the total dose according to the proposal by the Work Group report on OFC testing (ANW et al JACI 2009; Bird et al JACI 2020) and provide the patient with 25% of the total dose and observe for 2 hours and then if no reaction occurred the patient would be given the remainder 75% and observed for 4 hours. They also recommend that the patient have a baseline complete blood count (CBC) would be obtained prior to the challenge and again at 6 hours after the challenge if the patient has reactivity.

Disease resolution would be defined as passing an OFC without any reaction. Patients are then instructed to resume a serving size of food at least 2-3 times per week to maintain their tolerance.

Oral Food Challenge

An oral food challenge (OFC) for Food Protein-Induced Enterocolitis Syndrome (FPIES) is a procedure completed by a trained nurse and supervised by a physician in a medically supervised setting. Typically, the patient is given three equal doses of the suspected food over the period of an hour. The patient is then monitored for any reactions for at least four hours after the last dose. The nurse and the physician are available at all times to treat any reaction that may occur. Most reactions can be managed in the office; however, if the reaction is severe, the patient may be taken to the Emergency Room via ambulance for further observation and treatment. The plan for your child will be discussed when the challenge is scheduled and again on the day of the procedure.

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Why Undergo Challenge?
An OFC is useful for two purposes: it can confirm a suspected reaction and it can confirm tolerance. In the first scenario, providers may not be able to definitively tell if the symptoms of a reported reaction were 100% consistent with FPIES; maybe there were some atypical features or overlap with another potential diagnosis. In these cases, a confirmatory challenge can be very helpful to make sure the diagnosis fits.

In the second scenario, providers wish to test if your child is ready to re-introduce the food back into the diet. OFC is the ultimate “test” in FPIES and currently the only way to determine tolerance. There is no definitive answer as to when a patient is ready to be challenged. This may depend on the food involved or on the age of the patient. Commonly used “ready” points may be 12-24 months after the last reaction or when the child is between ages 3 to 5 years.

What Happens at a Challenge?

Pre-challenge: Once it is determined that your child is ready for a challenge, most providers will want to have seen your child for an office visit a few weeks or months before the challenge. This visit has multiple purposes:

  • To confirm that there has not been any accidental exposures (either one that resulted in symptoms or a significant exposure that resulted in tolerance that would make undergoing the challenge unnecessary);
  • To make sure that you and your child are fully prepared for the challenge experience;
  • To make sure that your child can/will eat a certain amount of the food;
  • To gauge your comfort in potentially witnessing a reaction and its treatment; and
  • To counsel you and review the challenge plan in advance of conducting the challenge.

At this visit, a thorough explanation of the challenge procedure and process should be reviewed and an opportunity to review and answer any questions you may have should be offered. Larger centers may have an additional follow-up call before the challenge from a team member to go over the logistics of the procedure and to make sure your child is not sick the week of the challenge. A sick child should not be challenged as it may increase the chance of reaction or produce confusion if symptoms occur that could be related to both the illness and underlying FPIES. This is also when the conduct of the challenge is discussed—advising that your child should eat a very light meal, that no outside food (generally) will be allowed during the challenge, and what to bring to entertain and comfort your child during the procedure.

Choice of Venue: A challenge can be conducted either in the doctor’s office/clinic or in the hospital. In the hospital, this is generally done as a day admission or short-stay observation and must be pre-arranged. In the office setting/clinic, this is also pre-arranged, but integrated into the normal clinic day. Some centers have a dedicated room or hospital units for these types of procedures. Other locations use a regular patient office room or hospital bed, or the OFC may be done in a clinical research center. The decision of venue choice may be based on your provider’s preference (in accordance with your wishes) and the availability of a non-office setting, but these options all provide a safe environment for your child. Setting up hospital-based procedures is much easier for certain providers to coordinate than for others. Challenges for FPIES can and are safe to conduct in the office.

Arrival: On arrival, full vital signs are taken, including weight. This is important because your child’s accurate weight helps determine the dose of food used. An IV may be placed as a precaution should there be a reaction, depending on the provider doing the challenge, the customs of the clinic/center where the challenge is being conducted, or your child’s personal circumstances. Not all providers will place an IV in advance, however, and some may elect to do so only if and when necessary. The provider supervising the procedure will examine your child and get your consent for the procedure. Full risks and benefits of the procedure should be explained, including the risk that the child may fail (meaning react) to the challenge and what potential treatments may be required.

The Procedure: There is a range of how much food to feed a child in a challenge. Commonly in the U.S., the dose may range between 0.15 to 0.3 grams of protein per kilogram of body weight (a kilogram is approximately 2.2 pounds). However, the range for the dose may span from 0.06 to 0.6 grams per kilogram. This will be determined by your physician. When possible, the most realistic serving size and vehicle for the food are chosen (e.g., a cup of milk or soy milk, a portion of oatmeal or rice, etc.). There are published tables of food protein contents that are used to aid in this process. The dose is calculated, and then the food item is carefully weighed and portioned.

The total dose is then typically divided into three equal portions. Each portion is fed at 20 minute intervals, with vital signs being monitored at each stage. Then, after the full portion has been eaten, the child is observed for upwards of 4-6 hours to make sure that no reaction occurs. The delayed nature of FPIES makes it necessary to watch the child for that long, given a 2 to 6 hour window in which a reaction is most likely to occur.

Keep in mind that the process described above is the recommended method according to the 2009 AAAAI Workgroup Report on Oral Food Challenges. However, some physicians may use different dosing strategies or observation times based on the patient’s history or their office/hospital’s policies.

If Your Child Reacts: While stressful, conducting challenges with a medical team’s supervision is done so that the focus remains on patient safety. While this may be a rather frightening thought, keep in mind that the challenge is being done in the provider’s office or hospital to protect your child. Allergists are trained at treating reactions and will have a plan mapped out in advance. IV fluid and an anti-nausea medication called Zofran have been documented to work well in treating a reaction, and these can both be administered at the clinic or hospital. Providers are present to closely monitor your child’s symptoms in the event of a reaction. All parties are aware that a challenge could result in a reaction, and this is why your child is closely monitored during the procedure.

The Aftermath: If your child is free of symptoms after the 4 to 6 hour observation period, a final exam will be performed, a last set of vital signs will be taken, and your child will be discharged home. It is normal that your child may be tired, hungry, irritable, or simply overwhelmed by the end of the day. Generally, parents are instructed to continue to observe the child at home for any late reactions, but if your child remains without symptoms, he/she can begin to eat this item on a regular basis.

There are many styles of how to integrate the food back into the diet. Your physician will discuss and outline a specific plan for your situation. In general, most providers urge caution and supervision at home with the next few trials of the challenge food, given that a small percentage may not react on the first re-exposure. After a few days of tolerance, your child should be able to safely eat this food. It is important to follow the instructions from your physician regarding the re-feeding plan and continue to re-feed your child to fully integrate the challenge food back into the diet.

Provided by the I-FPIES Medical Advisory Board

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