Rancé Fabienne, Abbal Michel, Lauwers-Cancès Valérie
Allergologie, Hôpital des Enfants, CHU Toulouse, Toulouse, France.
J Allergy Clin Immunol. 2002 Jun;109(6):1027-33. doi: 10.1067/mai.2002.124775.
The diagnosis of peanut allergy must be based on reliable, safe criteria. Double-blind, placebo-controlled food challenges (DBPCFCs) are the gold standard but are costly and dangerous because they can trigger severe reactions.
The aim of this study was to develop a new strategy for diagnosing peanut allergy while reducing the need for DBPCFCs.
We studied 363 children referred for an evaluation of suspected food hypersensitivity. They all benefited from the same diagnostic strategy, which included, in order, clinical history, a skin prick test (SPT), and a specific IgE assay. DBPCFCs were performed on all the children by personnel who were unaware of the results of the other tests. To assess the performance characteristics of the SPT (comparing commercial and raw peanut extracts) and the specific IgE assay, we compared the results with those provided by the DBPCFCs. For SPTs and specific IgE assays, we sought to determine the cutoff values required to exclude false-positive and false-negative results.
According to DBPCFC results, 177 children were allergic to peanut, and 186 were not. The performance characteristics of the SPTs were superior with the raw extract because the negative predictive value was 100% (95% confidence interval [CI], 97.5-100). If the skin reaction with the raw extract was less than 3 mm, we could be quite certain that the child was not allergic. On the other hand, if the SPT resulted in a wheal diameter of larger than 3 mm, we could only be 74% certain that the children were allergic. Furthermore, if the SPT resulted in a wheal diameter of 16 mm or larger, we could be quite certain that the child was allergic because the positive predictive value was 100% (95% CI, 86.8-100). Specific IgE concentrations of 57 kU(A)/L or greater were associated with a positive predictive value of 100% (95% CI, 87.2-100). The combined use of the tests resulting in a positive diagnosis if the SPT result was 16 mm or larger or specific IgE concentration was 57 kU(A)/L or greater and in a negative diagnosis if the SPT result was less than 3 mm and the specific IgE concentration was less than 57 kU(A)/L allowed us to classify subjects with almost complete certainty as being allergic or not because the predictive values were 100%.
Commercial extracts could not be used to reliably predict tolerance of peanut. Peanut DBPCFCs can be avoided when SPTs with raw extracts resulted in wheals with a largest diameter of less than 3 mm and a specific IgE concentration of less than 57 kU(A)/L and also when wheal diameters were 16 mm or larger or specific IgE values were 57 kU(A)/L or greater. Otherwise, DBPCFCs were indispensable for the unequivocal diagnosis of peanut allergy.
花生过敏的诊断必须基于可靠、安全的标准。双盲、安慰剂对照食物激发试验（DBPCFC）是金标准，但成本高昂且存在风险，因为它们可能引发严重反应。
本研究的目的是制定一种新的花生过敏诊断策略，同时减少对DBPCFC的需求。
我们研究了363名因疑似食物过敏而前来评估的儿童。他们都采用了相同的诊断策略，依次包括临床病史、皮肤点刺试验（SPT）和特异性IgE检测。由不知道其他检测结果的人员对所有儿童进行DBPCFC。为了评估SPT（比较商用和生花生提取物）和特异性IgE检测的性能特征，我们将结果与DBPCFC提供的结果进行了比较。对于SPT和特异性IgE检测，我们试图确定排除假阳性和假阴性结果所需的临界值。
根据DBPCFC结果，177名儿童对花生过敏，186名儿童对花生不过敏。生提取物的SPT性能特征更优，因为其阴性预测值为100%（95%置信区间[CI]，97.5 - 100）。如果与生提取物的皮肤反应小于3毫米，我们可以相当确定该儿童不过敏。另一方面，如果SPT导致风团直径大于3毫米，我们只能有74%的把握确定儿童过敏。此外，如果SPT导致风团直径为16毫米或更大，我们可以相当确定该儿童过敏，因为阳性预测值为100%（95%CI，86.8 - 100）。特异性IgE浓度为57 kU(A)/L或更高时，阳性预测值为100%（95%CI，87.2 - 100）。如果SPT结果为16毫米或更大或特异性IgE浓度为57 kU(A)/L或更高则诊断为阳性，而如果SPT结果小于3毫米且特异性IgE浓度小于57 kU(A)/L则诊断为阴性，联合使用这些检测可以让我们几乎完全确定地将受试者分类为过敏或不过敏，因为预测值为100%。
商用提取物不能可靠地预测对花生的耐受性。当使用生提取物进行SPT导致最大风团直径小于3毫米且特异性IgE浓度小于57 kU(A)/L时，以及当SPT风团直径为16毫米或更大或特异性IgE值为57 kU(A)/L或更高时，可以避免进行花生DBPCFC。否则，DBPCFC对于明确诊断花生过敏是必不可少的。
