Clark A T, Ewan P W
Department of Allergy and Clinical Immunology, Addenbrooke's Hospital, University of Cambridge Clinical School, Cambridge, UK.
Clin Exp Allergy. 2003 Aug;33(8):1041-5. doi: 10.1046/j.1365-2745.2003.01624.x.
Peanut and tree nut allergy are common, increasing in prevalence and the commonest food cause of anaphylaxis. In the USA, 7.8% are sensitized (have nut-specific IgE), but not all those sensitized are allergic. Lack of data makes interpretation of tests for nut-specific IgE difficult.
This is the first study to investigate the clinical significance of test results for peanut and tree nut allergy in allergic or tolerant patients. Findings are related to the severity of the allergy.
An observational study of 1000 children and adults allergic to at least one nut. History of reactions (severity graded) or tolerance to up to five nuts was obtained and skin prick test (SPT)/serum-specific IgE (CAP) performed.
There was no correlation between SPT size and graded severity of worst reaction for all nuts combined or for peanut, hazelnut, almond and walnut. For CAP, there was no correlation for all nuts. Where patients tolerated a nut, 43% had positive SPT of 3-7 mm and 3% > or = 8 mm. For CAP, 35% were positive (0.35-14.99 kU/L) and 5% > or = 15 kU/L. In SPT range 3-7 mm, 54% were allergic and 46% were tolerant. There was poor concordance between SPT and CAP (66%). Of patients with a clear nut-allergic history, only 0.5% had negative SPT, but 22% negative CAP.
Magnitude of SPT or CAP does not predict clinical severity, with no difference between minor urticaria and anaphylaxis. SPT is more reliable than CAP in confirming allergy. Forty-six per cent of those tolerant to a nut have positive tests > or = 3 mm (sensitized but not allergic). One cannot predict clinical reactivity from results in a wide 'grey area' of SPT 3-7 mm; 22% of negative CAPs are falsely reassuring and 40% of positive CAPs are misleading. This emphasizes the importance of the history. Understanding this is essential for accurate diagnosis. Patients with SPT > or = 8 mm and CAP > or = 15 kU/L were rarely tolerant so these levels are almost always (in > or = 95%) diagnostic.
花生和坚果过敏很常见，患病率呈上升趋势，是过敏反应最常见的食物诱因。在美国，7.8%的人对坚果致敏（具有坚果特异性IgE），但并非所有致敏者都过敏。缺乏数据使得对坚果特异性IgE检测结果的解读变得困难。
这是第一项调查花生和坚果过敏检测结果在过敏或耐受患者中的临床意义的研究。研究结果与过敏的严重程度相关。
对1000名对至少一种坚果过敏的儿童和成人进行观察性研究。获取反应史（严重程度分级）或对多达五种坚果的耐受性，并进行皮肤点刺试验（SPT）/血清特异性IgE（CAP）检测。
对于所有坚果综合起来或对于花生、榛子、杏仁和核桃，SPT大小与最严重反应的分级严重程度之间没有相关性。对于CAP，所有坚果之间均无相关性。在患者耐受某种坚果的情况下，43%的患者SPT呈阳性，直径为3 - 7毫米，3%的患者SPT直径大于或等于8毫米。对于CAP，35%呈阳性（0.35 - 14.99 kU/L），5%大于或等于15 kU/L。在SPT范围为3 - 7毫米的患者中，54%过敏，46%耐受。SPT和CAP之间的一致性较差（66%）。在有明确坚果过敏史的患者中，只有0.5%的患者SPT呈阴性，但22%的患者CAP呈阴性。
SPT或CAP的强度不能预测临床严重程度，轻度荨麻疹和过敏反应之间没有差异。在确认过敏方面，SPT比CAP更可靠。46%对某种坚果耐受的患者检测结果呈阳性，直径大于或等于3毫米（致敏但不过敏）。在SPT为3 - 7毫米的广泛“灰色区域”内，无法根据检测结果预测临床反应性；22%的CAP阴性结果会让人产生错误的安心感，40%的CAP阳性结果具有误导性。这强调了病史的重要性。理解这一点对于准确诊断至关重要。SPT大于或等于8毫米且CAP大于或等于15 kU/L的患者很少耐受，因此这些水平几乎总是（大于或等于95%）具有诊断意义。
