Comparison of skin prick test and prick-to-prick test with fruits and vegetables in the diagnosis of food allergy.

INTRODUCTION: Prick-to-prick (PTP) test with fresh food is accepted as a reliable tool for measuring sensitization to fruits and vegetables. Not all fruits and vegetables are available throughout the year. The objective of this study was to investigate whether skin prick test (SPT) performed with frozen juice of fruits and vegetables (FJFV) is a good alternative to PTP tests performed with fresh fruits and vegetables (FFV). METHODS: Adult patients suspected of having a food allergy to fruits and/or vegetables were included. A questionnaire was used to score symptoms after consumption of apple, kiwi, peach, tomato, and carrot. SPTs with FJFV, and PTP tests with FFV were performed. Intra-class correlation coefficients (ICC) between the SPT and PTP test results were calculated. The sensitivity and specificity of both diagnostic tests towards food allergen specific symptoms (FASS) were calculated. RESULTS: Thirty-six patients were included. FASS was positive in 75% for apple, 53% for kiwi, 44% for peach, 25% for tomato, and 22% for carrot. ICC between SPT and PTP test results were moderate for apple (0.72) and kiwi (0.71), strong for peach (0.75) and tomato (0.89), and very strong for carrot (0.94). Sensitivity was equal for the SPT and PTP tests for apple (0.93), peach (0.81), and carrot (1.00), and comparable for kiwi (0.50 resp. 0.70), and tomato (0.44 resp. 0.56). Specificity was equal for apple (0.33), peach (0.15), and carrot (0.41), and comparable for kiwi (0.29 resp. 0.21) and tomato (0.80 resp. 0.72). CONCLUSIONS: Results of SPT with FJFV and PTP test with FFV are comparable. SPT with FJFV is a good alternative in the daily practice of the allergists.

Homemade Food Allergen Extracts for Use in Skin Prick Tests in the Diagnosis of IgE-Mediated Food Allergy: A Good Alternative in the Absence of Commercially Available Extracts?

INTRODUCTION: The skin prick test (SPT) is the first step in the diagnosis of an immunoglobulin E (IgE)-mediated food allergy. The availability of commercial food allergen extracts is very limited, resulting in a need for alternative extraction methods of food allergens. The objective of this study was to compare the SPT results of homemade food allergen extracts with commercially available extracts. METHODS: Adult patients with a suspected food allergy were included. Food allergen-specific symptoms were scored using a questionnaire. SPTs were performed with homemade and commercially available extracts (ALK-Abelló, Kopenhagen, Denmark) from almond, apple, hazelnut, peach, peanut, and walnut. Serum-specific IgE was measured with ISAC or ImmunoCAP™. Intra-class correlation coefficients (ICC) between the SPT results of both extract methods were calculated. The proportion of agreement with food allergen-specific symptoms was analyzed. RESULTS: Fifty-four patients (mean age 36; range 19-69 years; female/male: 42/12) were included. The intra-class correlation coefficient (ICC) between the SPT results of both extract methods were strong for hazelnut 0.79 (n = 44) and walnut 0.78 (n = 31), moderate for apple 0.74 (n = 21) and peanut 0.66 (n = 28), and weak for almond 0.36 (n = 27) and peach 0.17 (n = 23). The proportion of agreement between SPT results and food allergen-specific symptoms was comparable for homemade and commercially available extracts, except for peach; 0.77 versus 0.36, respectively. CONCLUSION: In the diagnostic procedures to identify an IgE-mediated food allergy, homemade extracts from hazelnut and walnut appear to be a good alternative in the absence of commercially available food allergen extracts.