Keenan Research Center in the Li Ka Shing Knowledge Institute of St. Michael's Hospital, University of Toronto, Toronto, ON, Canada; Institute of Medical Science, University of Toronto, Toronto, ON, Canada.
Ottawa Hospital Research Institute, University of Ottawa, Ottawa, ON.
Chest. 2020 Aug;158(2):479-490. doi: 10.1016/j.chest.2020.03.052. Epub 2020 Apr 13.
In patients with a history suggestive of asthma, diagnosis is usually confirmed by spirometry with bronchodilator response (BDR) or confirmatory methacholine challenge testing (MCT).
We examined the proportion of participants with negative BDR testing who had a positive MCT (and its predictors) result and characteristics of MCT, including effects of controller medication tapering and temporal variability (and predictors of MCT result change), and concordance between MCT and pulmonologist asthma diagnosis.
Adults with self-reported physician-diagnosed asthma were recruited by random-digit dialing across Canada. Subjects performed spirometry with BDR testing and returned for MCT if testing was nondiagnostic for asthma. Subjects on controllers underwent medication tapering with serial MCTs over 3 to 6 weeks. Subjects with a negative MCT (the provocative concentration of methacholine that results in a 20% drop in FEV [PC] > 8 mg/mL) off medications were examined by a pulmonologist and had serial MCTs after 6 and 12 months.
Of 500 subjects (50.5 ± 16.6 years old, 68.0% female) with a negative BDR test for asthma, 215 (43.0%) had a positive MCT. Subjects with prebronchodilator airflow limitation were more likely to have a positive MCT (OR, 1.90; 95% CI, 1.17-3.04). MCT converted from negative to positive, with medication tapering in 18 of 94 (19.1%) participants, and spontaneously over time in 25 of 165 (15.2%) participants. Of 231 subjects with negative MCT, 28 (12.1%) subsequently received an asthma diagnosis from a pulmonologist.
In subjects with a self-reported physician diagnosis of asthma, absence of bronchodilator reversibility had a negative predictive value of only 57% to exclude asthma. A finding of spirometric airflow limitation significantly increased chances of asthma. MCT results varied with medication taper and over time, and pulmonologists were sometimes prepared to give a clinical diagnosis of asthma despite negative MCT. Correspondingly, in patients for whom a high clinical suspicion of asthma exists, repeat testing appears to be warranted.
在有哮喘病史提示的患者中，通常通过支气管扩张剂反应（BDR）或确认性乙酰甲胆碱挑战测试（MCT）来确认诊断。
我们检查了接受阴性 BDR 测试的参与者中，阳性 MCT（及其预测因素）结果的比例，以及 MCT 的特征，包括控制器药物减量和时间变异性（以及 MCT 结果变化的预测因素）的影响，以及 MCT 与肺科医生哮喘诊断之间的一致性。
通过加拿大各地的随机数字拨号，招募有自我报告的医生诊断为哮喘的成年人。受试者进行支气管扩张剂反应的肺量测定，如果测试对哮喘无诊断意义，则返回进行 MCT。接受控制器治疗的受试者在 3 至 6 周内进行了药物减量和连续 MCT。在停药后 MCT 阴性（导致 FEV [PC] 下降 20%的乙酰甲胆碱浓度 > 8mg/mL）的患者中，由肺科医生进行检查，并在 6 和 12 个月后进行连续 MCT。
在 500 名（50.5±16.6 岁，68.0%女性）哮喘阴性 BDR 测试的受试者中，215 名（43.0%）的 MCT 为阳性。有预支气管扩张剂气流受限的受试者更有可能出现阳性 MCT（比值比，1.90；95%置信区间，1.17-3.04）。18 名（19.1%）接受药物减量的受试者和 25 名（15.2%）自主随时间变化的受试者，MCT 从阴性转为阳性。在 231 名 MCT 阴性的受试者中，28 名（12.1%）随后被肺科医生诊断为哮喘。
在有自我报告的医生诊断为哮喘的患者中，支气管扩张剂可逆转性缺失的阴性预测值仅为 57%，不足以排除哮喘。肺量测定显示气流受限显著增加了哮喘的可能性。MCT 结果随药物减量和时间变化而变化，尽管 MCT 呈阴性，但肺科医生有时也准备做出哮喘的临床诊断。相应地，对于那些存在高度临床怀疑哮喘的患者，似乎需要重复进行测试。
