Abisheganaden J, Chan C C, Chee C B, Wang Y T
Department of Respiratory Medicine, Tan Tock Seng Hospital, Singapore.
Respir Med. 1999 Apr;93(4):277-82. doi: 10.1016/s0954-6111(99)90025-2.
The dose of methacholine causing a 20% fall in forced expiratory volume in 1 sec (FEV1) from baseline (PD20) has been used as an index of asthma severity. The aim of this study was to determine if the percentage fall in forced vital capacity (FVC) from baseline at the PD20 (dFVC%) is an independent marker of asthma severity. We first retrospectively studied the dFVC% and PD20 obtained from 149 consecutive newly diagnosed asthmatics with a positive methacholine-challenge test (MCT). We then performed MCT on 20 normal subjects and 35 stable asthmatics. The 'milder' asthmatics (n = 20) and 'more severe' asthmatics (n = 15) were on regular inhaled corticosteroids: 200 micrograms or less and 800 micrograms or more daily, respectively. A dosimeter technique was used, and normal subjects were given a cumulative dose of 2400 micrograms. The PD20 and dFVC% were calculated using log-linear interpolation of the last two points. Student's unpaired t-tests and linear regression analyses were used for comparison and correlation of results. There was no significant correlation between dFVC% and PD20 among the 149 newly diagnosed asthmatics (r = 0.1), or among the 35 known stable asthmatics (r = 0.008). The more severe asthmatics had a larger dFVC% compared with the milder asthmatics (15.8% vs. 9.6%; P = 0.0005). In addition, inhaled corticosteroid usage correlated better with dFVC% (r = 0.56) than with PD20 (r = 0.36). The normal subjects had a mean fall in FVC of only 4.8%. The percentage fall in FVC at PD20 (dFVC%) may be a useful index of asthma severity which is independent of PD20. This index is potentially complementary to the PD20 in the assessment of asthma severity.
使一秒用力呼气量（FEV1）较基线水平下降20%的乙酰甲胆碱剂量（PD20）已被用作哮喘严重程度的指标。本研究的目的是确定在PD20时用力肺活量（FVC）较基线水平下降的百分比（dFVC%）是否为哮喘严重程度的独立标志物。我们首先回顾性研究了149例连续新诊断的、乙酰甲胆碱激发试验（MCT）阳性的哮喘患者的dFVC%和PD20。然后我们对20名正常受试者和35名稳定期哮喘患者进行了MCT。“病情较轻”的哮喘患者（n = 20）和“病情较重”的哮喘患者（n = 15）分别规律吸入皮质类固醇：每日200微克及以下和800微克及以上。采用剂量计技术，给正常受试者给予2400微克的累积剂量。使用最后两点的对数线性插值法计算PD20和dFVC%。采用学生非配对t检验和线性回归分析对结果进行比较和相关性分析。在149例新诊断的哮喘患者中，dFVC%与PD20之间无显著相关性（r = 0.1），在35例已知的稳定期哮喘患者中也无显著相关性（r = 0.008）。与病情较轻的哮喘患者相比，病情较重的哮喘患者dFVC%更大（15.8%对9.6%；P = 0.0005）。此外，吸入皮质类固醇的使用与dFVC%的相关性（r = 0.56）优于与PD20的相关性（r = 0.36）。正常受试者的FVC平均下降仅4.8%。在PD20时FVC下降的百分比（dFVC%）可能是一个有用的哮喘严重程度指标，且独立于PD20。该指标在评估哮喘严重程度方面可能是对PD20的潜在补充。
