Comparing pediatric cashew oral food challenges practice between London and Geneva

To the Editor, Cashew (Anacardium occidentale) is considered a seed belonging to the Anacardiaceae family growing on the bottom of the cashew apple.1 Cashew allergy is increasing, and it is one of the most common nut allergies in the United Kingdom2– 6 and in Switzerland.7 Physicians and patients should be aware of cashew's potential crossreactivity to other allergens in a wide range of foods, that can represent possible clinically relevant allergic triggers, for example, pistachio or pink peppercorn.8 Children allergic to cashew need to strictly avoid the food and carry appropriate emergency medications as severe allergic reactions are possible. Given the risk of severe reactions and its impact on quality of life, a rigorous diagnosis of cashew allergy is required. The oral food challenge (OFC) to cashew remains the gold standard diagnostic investigation. However, protocols are not universally standardized, even if they are increasingly described. In an OFC, the allergen is administered in titrated doses that are increased at set intervals until reaching an ageappropriate target dose, if tolerated. There are many variables in this process including patientrelated factors, allergy clinic resources, challenge protocols, and the form in which food is eaten.9 Audit of routine clinical service aims to improve clinical practice. However, information is rarely exportable to other geographic populations, due to several factors, such as different patient characteristics and allergy clinic protocols. Data regarding the comparison of the reallife practice OFCs between different centers are lacking for common food allergens other than peanut. Indeed, a previous analysis on the comparison of the practice of peanut OFC between London and Western Switzerland pointed out several interesting similarities and differences.10 In the current work, we carried out a retrospective, observational, and bicentric databasebased study to compare the practice of cashew OFCs between two tertiary level pediatric centers in London and Geneva. Detailed information on the methods can be found in the Appendix S1 section. During the period taken into consideration, a total of 144 cashew OFCs were performed: 90 in London and 54 in Geneva, with 88 (males 59.09%; mean age ± standard deviation, SD 6.00 ± 4.36 years) and 54 patients (males 59.26%; mean age ± SD 6.57 ± 3.32 years) involved, respectively. Table 1 presents general patient characteristics, cashew serumspecific Immunoglobulin E (sIgE) levels, and key outcomes of the cashew OFCs. British and Swiss population demonstrated comparable features in terms of gender and age (pvalue not statistically significant, n.s.). Concerning sensitization, the mean ± SD cashew sIgE levels recorded were also similar in London and Geneva (1.56 ± 3.69 kU/L and 2.36 ± 8.67 kU/L, respectively; pvalue n.s.). Among the 144 cashew OFCs, there was a lower rate of positive tests in London compared to Geneva, with 15/90 (16.67%) versus 22/54 (40.74%) positive OFCs, respectively (p < .05). Table 2 presents general characteristics, cashew sIgE levels, and key outcomes of patients with positive OFCs. Among positive cashew OFCs, differences were noted in rates of anaphylaxis, being lower in London compared to Geneva (3/15, 20.00% versus 16/22, 72.73%, respectively, p < .05). However, British and Swiss populations demonstrated comparable features in terms of clinical manifestations and their onset during cashew OFC (pvalue n.s.). Regarding the medications used to treat the reactions, populations in London and Geneva demonstrated comparable use of adrenaline, antihistamines, and bronchodilators (pvalue n.s.), but a lower use of corticosteroids was recorded in London than in Geneva, in 1/15 (6.67%) versus 9/22 (40.9%) of positive cashew OFCs, respectively (p < .05). Prednisolone was used as a corticosteroid in the two centers. Furthermore, first generation antihistamines were used in London but not in Geneva. In the same centers, when assessing differences for peanut, we found the children in the British cohort were younger than the Swiss cohort (p < .05).10 The target cumulative peanut protein dose in the OFC design was higher in London. The mean peanut sIgE level was lower in the British cohort (p < .05), and a lower occurrence of positive OFCs was demonstrated when compared to Geneva (p < .05). These differences in peanut OFC outcomes were hypothesized to arise due to London performing them more on peanutsensitized patients with no history of exposure to the food, in contrast to Geneva performing them more on patients sensitized to peanut and with a history of reaction to the food.10 A clinical service that undertakes OFCs needs to set their optimal target servicepositive OFC rate, which in London is lower than in Geneva.10 A higher rate of OFCs may also be associated with a greater proportion of anaphylactic reactions. Of note, all of the anaphylaxis cases which occurred in London were recorded in patients who were candidates to perform a cashew OFC with a single top dose only (supervised feed), which was at the discretion of the clinician who evaluated the patient and