The situation you described is not an uncommon one, and most allergists base the types of decisions you must make at some time during their practice. Recognizing this, the Joint Task Force has devoted a section of the most recent Allergen Immunotherapy Parameters (1) to this issue. This entire reference is of course available to you online, but for your convenience, I have copied the most applicable section below.
As you can see, it does address each of your concerns, but oftentimes simply leaves the answer to these questions up to the clinical judgment of the physician involved. For example, each individual physician should make a decision as to whether or not they would continue allergen immunotherapy in a new patient, decide whether or not retesting might be indicated, et cetera. These are individual clinical decisions which are made in cooperation with the patient.
Also, at the end of this section, a suggestion as to how dosages may be altered based upon whether or not the same or a different manufacturer is used. In addition, you can usually obtain information as to how to make such adjustments by contacting the vaccine supplier and asking them what their suggestions are when changes from one supplier to the next are made.
The general principle of course is to maintain safety, and oftentimes that might require you to lower the dose extensively.
Thank you again for your inquiry and we hope this response is helpful to you.
1.Cox L, Nelson H, Lockey R, et al. Allergen immunotherapy: a practice parameter, third update. Journal of Allergy and Clinical Immunology, January 2011; Volume 127 (1), Supplement, page S1-S55.
Transferring allergen immunotherapy care:
Summary Statement 66: If a patient receiving immunotherapy transfers from one physician to another, a decision must be made by the physician to whom the patient has transferred as to whether to continue immunotherapy. D
Summary Statement 67: If immunotherapy is continued, a decision must then be made about whether to continue unchanged the immunotherapy program initiated by the previous physician or to start a new immunotherapy program. Patients can continue to receive the immunotherapy extract prepared by the patient’s previous physician if this is acceptable to the transferring and accepting physicians. D
Patients may transfer from one physician (previous physician) to another (current physician) while receiving allergen immunotherapy. When this occurs, a decision must be made by the current physician about whether to continue immunotherapy and, if so, what allergen immunotherapy extract and schedule should be used: the one that the patient received from the previous physician (ie, an unchanged immunotherapy program) or one to be prepared by the current physician (ie, a new immunotherapy program).
The current physician might choose to prepare a new allergen immunotherapy extract formulation based on the immunotherapy prescription or allergy test results from the previous physician, if the records provide adequate details. If there is inadequate information in the immunotherapy prescription documentation to continue the previous immunotherapy program, re-evaluation might be necessary, and a new schedule and allergen immunotherapy extract formulation might be prescribed.
Summary Statement 68: A detailed documentation of the patient’s schedule and allergen extract content must accompany a patient when he or she transfers responsibility for immunotherapy care from one physician to another. In addition, a record of previous response to and compliance with this program should be communicated to the patient’s new physician. D
If the patient transfers from one physician to another and continues on the previous immunotherapy program without changing either the schedule or allergen immunotherapy extract, he or she is not at substantially increased risk of having systemic reactions as long as there is a clear and detailed documentation of the patient’s previous schedule and the contents of the allergen immunotherapy extract. The patient’s immunotherapy administration documentation must accompany the patient who transfers responsibility for the immunotherapy program from one physician to another. This should include a record of any reactions to immunotherapy and how they were managed, as well as the patient’s response to immunotherapy. Under these circumstances, immunotherapy can be continued with the allergen immunotherapy extract that the patient was previously receiving if (1) the previous physician is willing and able to continue to provide the patient with the allergen immunotherapy extract, (2) the patient has shown significant improvement on this immunotherapy program, (3) the contents of the allergen immunotherapy extract are appropriate for the area in which the patient is now living, and (4) all extracts are well identified and the records are clear (see Tables E7-E15 in this article’s Online Repository at www.jacionline.org for documentation guidelines and examples of allergen immunotherapy prescription and administration forms).
Summary Statement 69: An allergen immunotherapy extract must be considered different if there is any change. There is potentially an increased risk of a systemic reaction if the immunotherapy extract is changed because of the possible variability in the composition and potency of allergen extracts. If the allergen immunotherapy extract is changed, the patient might need to be retested for specific IgE sensitivity and started on an immunotherapy formulation and schedule that is based on this re-evaluation. D
An allergen immunotherapy extract must be considered different from a clinical standpoint if there is any change in the constituents of the allergen immunotherapy extract. These include changes in the lot, manufacturer, extract type (eg, aqueous, glycerinated, standardized, and nonstandardized), and component allergens and their respective concentrations in the allergen immunotherapy extract. There is potentially an increased risk of a systemic reaction if the allergen immunotherapy extract is changed and the patient’s dose is not modified. This increased risk might be due to the significant variability in content and potency of extracts and the variability in methods used by physicians to prepare the patient’s immunotherapy extract. For example, the strength of a given concentration of nonstandardized extracts might vary significantly from lot to lot. The risk of systemic reactions might be greater with nonstandardized extracts because of this potential variability in the composition and/or potency.
If the allergen immunotherapy extract is to be changed, the patient might need to be retested for allergen-specific IgE and started on an immunotherapy schedule and immunotherapy extract formulation that is appropriate. In this situation the starting dose should be comparable with the initial dose that would be used if the patient had not previously been receiving immunotherapy. If the information that accompanies the patient is thorough, the current physician can prepare an allergen immunotherapy extract identical or almost identical to that provided by the previous physician. In such a case all that might be required is a decrease in the dose from the patient’s previous injection if there has not been too long an interval since the last injection. For lot changes from the same manufacturer, the physician can consider decreasing the dose by 50% to 90% of the previous dose. For changes in manufacturer and nonstandardized extracts, a greater decrease in dose might be necessary.
Phil Lieberman, M.D.