Brettig T, Dang T, McWilliam V, et al. - By performing a systematic review, researchers assessed the diagnostic capacity of clinical tests (Skin Prick Test, specific IgE, Component Resolved Diagnostics, Basophil Activation Test) to ascertain oral food challenge confirmed or clinical tree nut allergy. Four electronic databases (OVID Medline, Embase, Cochrane library and PubMed) were explored to identify eligible studies. Only reasonable accuracy of diagnostic testing was reported, with 95% positive predictive values established in a small number of tree nuts. Cashew was found to have the best diagnostic accuracy, the most predictive was the cashew component Ana o 3. Findings underscore the limitations of current diagnostic instruments for tree nut allergy and highlight further aspects for exploration. Herein, the uni-directionality of cross-reactivity between cashew/pistachio and walnut/pecan was defined and can assist diagnosis. Greater diagnostic accuracy as well as decreased number of oral food challenges may be achieved by using diagnostic algorithms such as those demonstrated for walnut/pecan and cashew/pistachio allergy.