Vandenplas O, Delwiche J P, Jamart J, Van de Weyer R
Department of Chest Medicine, Mont-Godinne Hospital, Catholic University of Louvain, Belgium.
Thorax. 1996 May;51(5):472-8. doi: 10.1136/thx.51.5.472.
Specific bronchial reactivity to occupational agents may decline after exposure in the workplace ceases leading to falsely negative specific inhalation challenges. A study was carried out to assess prospectively whether increases in nonspecific bronchial hyperresponsiveness could be useful in detecting the bronchial response to occupational agents during specific inhalation challenges.
Specific inhalation challenges were performed in 66 subjects with possible occupational asthma due to various agents. After a control day the subjects were challenged with the suspected agent for up to two hours on the first test day. Those subjects who did not show an asthmatic reaction were rechallenged on the next day for 2-3 hours. The provocative concentration of histamine causing a 20% fall (PC20) in the forced expiratory volume in one second (FEV1) was assessed at the end of the control day as well as six hours after each challenge that did not cause a > or = 20% fall in FEV1. The subjects who had a significant (> or = 3.1-fold) reduction in PC20 value at the end of the second challenge day were requested to perform additional specific inhalation challenges.
The first test day elicited an asthmatic reaction in 25 subjects. Of the other 41 subjects five (12%, 95% confidence interval (CI) 4% to 26%) exhibited a > or = 3.1-fold fall in the PC20 value after the inhalation challenge and developed an asthmatic reaction during the second (n = 3) or third (n = 2) challenge exposure. The offending agents included persulphate (n = 1), wood dust (n = 2), isocyanate (n = 1), or amoxycillin (n = 1). These five subjects had left their workplace for a longer period (mean (SD) 21 (14) months) than those who reacted after the first specific inhalation challenge (8 (11) months).
The increase in non-specific bronchial hyperresponsiveness after a specific inhalation challenge can be an early and sensitive marker of bronchial response to occupational agents, especially in subjects removed from workplace exposure for a long time. Non-specific bronchial hyperresponsiveness should be systematically assessed after specific inhalation challenges in the absence of changes in airway calibre.
对职业性致病因素的特异性支气管反应性在停止工作场所暴露后可能会下降，从而导致特异性吸入激发试验出现假阴性结果。开展了一项研究，前瞻性评估非特异性支气管高反应性的增加在特异性吸入激发试验期间检测支气管对职业性致病因素反应方面是否有用。
对66名因各种致病因素可能患有职业性哮喘的受试者进行特异性吸入激发试验。在一个对照日后，受试者在第一个试验日接受可疑致病因素激发长达两小时。那些未出现哮喘反应的受试者在次日再次接受激发2至3小时。在对照日结束时以及每次未导致第一秒用力呼气量（FEV1）下降≥20%的激发后6小时，评估引起FEV-1下降20%的组胺激发浓度（PC20）。在第二个激发日结束时PC20值显著（≥3.1倍）降低的受试者被要求进行额外的特异性吸入激发试验。
第一个试验日有25名受试者出现哮喘反应。在其他41名受试者中，5名（12%，95%置信区间（CI）4%至26%）在吸入激发后PC20值下降≥3.1倍，并在第二次（n = 3）或第三次（n = 2）激发暴露期间出现哮喘反应。致病因素包括过硫酸盐（n = 1）、木尘（n = 2）、异氰酸酯（n = 1）或阿莫西林（n = 1）。这5名受试者离开工作场所的时间（平均（标准差）21（14）个月）比在第一次特异性吸入激发试验后出现反应的受试者（8（11）个月）更长。
特异性吸入激发试验后非特异性支气管高反应性的增加可能是支气管对职业性致病因素反应的早期敏感标志物，尤其是在长时间脱离工作场所暴露的受试者中。在气道口径无变化的情况下，特异性吸入激发试验后应系统评估非特异性支气管高反应性。
