Miles J, Cayton R, Ayres J
Chest Research Institute, Birmingham Heartlands Hospital, UK.
Clin Exp Allergy. 1995 Nov;25(11):1074-82. doi: 10.1111/j.1365-2222.1995.tb03254.x.
Sensitization to inhaled and ingested allergens is an important process in determining the subsequent clinical expression of asthma. Allergen exposure has also been reported to be associated with admission to hospital with acute severe asthma. Patients with brittle asthma, characterized by widely variable peak expiratory flow are at increased risk of life-threatening episodes but the role of atopy in these patients is unknown.
To determine the atopic status of patients with brittle asthma using a case-control design.
We have assessed the atopic status by skin-prick tests to 19 common allergens, and total and specific immunoglobulin E (IgE) in 29 patients with well characterized brittle asthma and an age, sex and treatment-matched control group without brittle asthma.
Mean weal diameters were higher in brittle compared to non-brittle asthma for grass pollen (4.64 vs 2.17; P = 0.01), horse hair (6.28 vs 2.64; P = 0.02), feathers (2.96 vs 1.52; P = 0.01), wheat (1.48 vs 0.66; P = 0.001) and chocolate (1.09 vs 0.41; P = 0.05). Mean radioallergosorbent (RAST) scores to house dust mite were also greater in brittle asthma patients (19.3 vs 7.65; P = 0.05). Patients with brittle asthma also exhibited a significantly greater degree of atopy when weal diameters to all 19 allergens were summated to produce an atopy score (brittle 44.35 vs non-brittle 23.72; P = 0.04). There were no significant differences between the two groups in either the number of positive skin tests (using a 4 mm definition of skin-test positivity), total IgE or RASTs (using a weak +ve score to define positivity). However, the use of differing definitions of atopy (1, 2, 3, 4 and 5 mm skin test weal diameters) resulted in marked intra-group variation in atopic status in both brittle and non-brittle asthma patients.
The greater degree of atopy seen may be an important factor in patients with brittle asthma. The varying interpretations of the classification of what constitutes the presence or absence of atopy, based on mean weal diameters of skin-prick tests, or from IgE or RAST positivity shows that there is considerable potential variation in the degree of difference between the two groups depending on what criteria are used. Although internationally agreed definitions of atopic status have been devised a more rigorous application, or review of these guidelines needs to accompany future epidemiological studies of allergic sensitization.
对吸入性和食入性过敏原的致敏作用是决定哮喘后续临床症状的一个重要过程。据报道，过敏原暴露还与急性重症哮喘患者入院治疗有关。脆性哮喘患者的特点是呼气峰值流速变化很大，其发生危及生命发作的风险增加，但特应性在这些患者中的作用尚不清楚。
采用病例对照设计确定脆性哮喘患者的特应性状态。
我们通过对19种常见过敏原进行皮肤点刺试验，以及检测29例特征明确的脆性哮喘患者和一组年龄、性别及治疗情况相匹配的非脆性哮喘对照组患者的总免疫球蛋白E（IgE）和特异性IgE，来评估特应性状态。
与非脆性哮喘相比，脆性哮喘患者对草花粉（风团平均直径4.64对2.17；P = 0.01）、马毛（6.28对2.64；P = 0.02）、羽毛（2.96对1.52；P = 0.01）、小麦（1.48对0.66；P = 0.001）和巧克力（1.09对0.41；P = 0.05）的风团平均直径更大。脆性哮喘患者对屋尘螨的平均放射变应原吸附试验（RAST）评分也更高（19.3对7.65；P = 0.05）。当将对所有19种过敏原的风团直径相加得出特应性评分时，脆性哮喘患者的特应性程度也显著更高（脆性哮喘组为44.35，非脆性哮喘组为23.72；P = 0.04）。两组在皮肤试验阳性数量（采用4 mm作为皮肤试验阳性的定义）、总IgE或RAST（采用弱阳性评分定义阳性）方面均无显著差异。然而，采用不同的特应性定义（皮肤试验风团直径为1、2、3、4和5 mm）导致脆性和非脆性哮喘患者组内特应性状态存在明显差异。
观察到的更高程度的特应性可能是脆性哮喘患者的一个重要因素。基于皮肤点刺试验的风团平均直径、IgE或RAST阳性与否对特应性存在与否的分类的不同解读表明，根据所使用的标准，两组之间差异程度存在相当大的潜在变化。尽管已经制定了国际公认的特应性状态定义，但在未来关于过敏性致敏的流行病学研究中需要更严格地应用或审查这些指南。
