Use of Food Allergy Panels by Pediatric Care Providers Compared With Allergists

Discussion

To our knowledge, this is the first study to quantify and characterize the use of food allergen sIgE tests by PCPs. Our findings demonstrate significant discrepancies in the quantity and cost associated with ordering food allergen panels by PCPs compared with allergists. In addition, PCPs were more likely to order single-food sIgE tests for foods that are infrequent causes of allergy in children, such as strawberry, beef, and tomato. PCPs further removed from residency training ordered more sIgE tests overall, especially panels, which suggests a possible lack of understanding or slow adoption of up-to-date food allergy clinical guidelines.⁶ Collectively, these findings reflect a need for additional education to ensure the most appropriate ordering and interpretation of sIgE tests for the evaluation of food allergy.

The discrepancy in use of sIgE panels was most apparent in orders for the Childhood Allergy Profile, which was only ordered 2 times during the study period by allergists, compared with 383 orders from PCPs. This profile contains 5 aeroallergens (cat, dog, dust mite, cockroach, and alternaria) that rarely cause clinical symptoms in infants <12 months of age who may be suspected of having food allergies. Understanding of the components of each panel as well as clinical relevance is important in both ordering the proper test and interpretation of results.

The clinical history is the most important factor when determining whether a food allergy may be present.⁹ Historical elements of importance include the type of food reported to cause symptoms, timing of symptom onset, types of symptoms, and recurrence of symptoms with subsequent ingestion of the food in question.^3,6 In children, egg, cow’s milk, and peanut allergies are most common,^2,14,15 whereas peanut, tree nuts, and seafood allergies are more common in adults.¹⁶ Knowledge of the important historical elements, spectrum of food-related adverse reactions, and common causes of IgE-mediated food allergy is important to determine which foods may warrant testing and also to avoid unnecessary testing.^17–22

In 2012, the American Board of Internal Medicine and American Academy of Allergy, Asthma and Immunology published their first Choosing Wisely series, which highlights 10 areas of unnecessary testing.²³ Number 7 on this list states: “Don’t perform food IgE testing without a history consistent with potential IgE-mediated food allergy.” There is also no indication to remove food from someone’s diet based solely on a “positive” sIgE result. Many patients may be sensitized with a detectable sIgE to foods but not experience any reactions with exposure.¹¹ Both skin prick and serum-specific IgE testing for foods have high rates of falsely elevated results.²⁴ This can result in misinterpretation, improper diagnosis, and unnecessary dietary elimination. In addition, the 95% positive predictive values have only been established for egg, milk, and peanut.²⁵ Positive predictive values for other common allergenic foods, such as fish and tree nuts, are not as well established.⁵ Thus, interpretation of sIgE levels to any other foods is based on clinical history and experience of the ordering physician.

In a recent study, Bird et al¹⁰ demonstrated the unnecessary clinical and economic burden associated with use and misinterpretation of food sIgE panels by PCPs. Among 797 children referred to their A/I practice over 18 months, 35% had previous food allergy panel testing. The authors determined the positive predictive value of panel testing for food allergy to be 2.2%. They also found that only 32.8% had a clinical history that warranted food allergy evaluation and there was an avoidable cost of ∼$79 000 associated with these evaluations.

We previously identified knowledge gaps surrounding food allergies among internal medicine and pediatric residents and attending physicians at 2 large academic medical centers.²⁶ In this study, 408 physicians answered a 9-question survey, including 6 questions related to food allergy diagnosis, testing, or management. Only 22% of respondents correctly answered a question regarding sIgE testing for food allergies and only 27% correctly identified the most common childhood food allergens. Overall, physicians with previous A/I elective experience or who recently completed residency training had the highest number of correct answers.

A survey published in 2007 identified significant differences in the understanding of prevalence, causes, and presentation of food allergies among nonallergists compared with allergists.²⁷ Nonallergists were more likely to misidentify common causes of food allergy, order nonvalidated diagnostic tests, and recommend broader elimination diets when compared with allergists.²⁸ A similar survey by Gupta et al²⁹ was published in 2010. In this survey of 407 pediatricians and family practitioners, 68% of PCPs responded that a positive sIgE is sufficient to diagnose food allergy and only 28% felt comfortable interpreting laboratory tests to diagnose food allergy.²⁹

Lack of understanding of food allergies and testing by PCPs is multifactorial but likely related to demands on their time and challenges in keeping up with an ever-growing body of evolving scientific evidence and changing clinical guidelines. Limited access to board-certified A/I consultants for patient referrals or A/I training programs for residency elective rotations may contribute as well.

In our study, specialists in other fields, NPs, and PAs ordered 21.3% of all sIgE tests. Similar to PCPs, this group of clinicians collectively ordered food allergen panels (31.7%) more frequently than allergists. Given the widespread availability of sIgE testing, which can be ordered by any provider, educational efforts should not only be directed at PCPs, but other specialists and NP/PAs as well.

Strengths of our study include the large number of laboratory orders and physicians included in the database, details regarding types of food allergen sIgE orders placed, and inclusion of the duration of practice for each physician. Major limitations include an inability to assess the clinical history of any patients who had testing performed or the interpretation and management of the test results. In addition, the cost analysis does not take into account any other charges, such as office visits, follow-up skin prick testing, oral food challenges, or provision of epinephrine auto-injectors. However, given the findings from Bird et al,¹⁰ it is reasonable to extrapolate that the sheer volume of sIgE panels ordered by providers in our study would lead to considerable additional cost and likely unnecessary dietary elimination.

The availability of serum IgE testing for PCPs is extremely important for their ability to evaluate patients with potential food allergy, particularly if access to allergists and/or skin prick testing is limited. However, to avoid unnecessary cost and potential misinterpretation, PCPs should refrain from ordering any sIgE panel tests containing foods, particularly if the clinical history is not suggestive for IgE-mediated food allergy. In support of this, the first recommendation from the Choosing Wisely list states: “Don’t perform unproven diagnostic tests, such as immunoglobulin G testing or an indiscriminate battery of IgE tests, in the evaluation of allergy²³.” Instead, PCPs should evaluate concern for food allergy by ordering individual sIgE tests only to foods for which there is a clinical history consistent with IgE-mediated food allergy. Ideally, commercial laboratories would consider removing sIgE panels containing foods from their available tests to prevent unnecessary cost expenditures.

Medical societies, clinical guidelines, and allergists can all serve as potential resources for educational efforts to help increase the knowledge and understanding of PCPs in regard to the ordering and interpretation of food sIgE testing. Future research should include confirmation of our findings in other geographic locations and patient populations as well as evaluation of trends over time. In addition, large scale studies with inclusion of clinical outcomes would offer broader insight into the potential impact from use of food allergy sIgE panels.