Lipid transfer protein cross-reactivity assessed in vivo and in vitro in the office: pros and cons.

BACKGROUND Few studies analyze cross-reactivity between lipid transfer proteins (LTP) from a large spectrum of botanically unrelated plant-derived foods using routine diagnostic tests. OBJECTIVE To assess the clinical usefulness of currently available in vivo and in vitro tests in LTP-hypersensitive patients. METHODS An in vitro and in vivo study was performed of 15 peach-allergic adults monosensitized to LTP in order to analyze their allergy and hypersensitivity to apple, hazelnut, walnut, peanut, soybean, lentil, maize, celery, carrot, banana, melon, tomato, kiwi, buckwheat, and sunflower, poppy, mustard, and sesame seeds. RESULTS The study revealed that 8, 7, 10, 5, 3, 2, 1, 1, and 1 patients were allergic to apple, hazelnut, walnut, peanut, tomato, kiwi, melon, lentil, and maize, respectively. Immunoglobulin (Ig) E levels for peach were strongly associated with the total number of offending foods other than peach and with levels of IgE specific for all the study foods except carrot. Both in vivo and in vitro tests showed excellent sensitivity and negative predictive value, but poor specificity and positive predictive value. Sensitized but tolerant patients showed lower IgE levels than those with a history of local or systemic symptoms, although the difference between the 3 subsets was not statistically significant. CONCLUSION This study confirms that peach is the primary sensitizer to LTP and that the level of IgE to peach LTP is the main factor associated with cross-reactivity (and clinical allergy) to non-Rosaceae foods. Clinically irrelevant sensitization is common in LTP-hypersensitive patients, and positive in vivo and/or in vitro test results are of little help in detecting potential clinical reactors.