title: Response--dose ratio is a surrogate of cumulative provocative dosage for bronchial provocation tests in asthma.
abstract: BACKGROUND
  Response-dose ratio (RDR) and cumulative provocative dosage (PD) are useful indices reflecting airway responsiveness in asthma.
  
  
  OBJECTIVE
  To compare the diagnostic value of RDR and PD, by conducting leukotriene D4 (LTD4-BPT) and methacholine bronchial provocation test (MCh-BPT), in different asthma control levels.
  
  
  METHODS
  Healthy subjects and asthmatic patients underwent LTD4-BPT and MCh-BPT, at 2-14-day interval. This entailed assessment of the distribution characteristics, correlation, and diagnostic value of PD inducing 20% fall in forced expiratory volume in one second (PD20FEV1) and the RDR, defined as FEV1 fall (%) at the final step divided by the corresponding provocative dosage.
  
  
  RESULTS
  Twenty uncontrolled, 22 partly controlled, 20 controlled asthmatics, and 21 healthy subjects were enrolled. Log10RDR was positively correlated with log10PD20FEV1 in both BPTs (all P < 0.05). Poorer asthma control was associated with significantly lower PD20FEV1 and higher RDR (both P < 0.05). The differences in PD20FEV1 and RDR between partly controlled and controlled asthma were unremarkable (both P > 0.05). Compared with log10PD20FEV1, the log10RDR yielded similar diagnostic values in both BPTs. A lower percentile of RDR (≤ 25th percentile) was associated with higher baseline FEV1 (P < 0.05) and an increased proportion of well-controlled asthmatic patients. The combination of RDR and PD20FEV1 led to an increased diagnostic value compared with either parameter alone.
  
  
  CONCLUSIONS
  RDR is a surrogate of PD20FEV1 for BPTs in asthma. This finding was not modified by different asthma control levels or the types of bronchoprovocants.
authors: State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical University, 151 Yanjiang Road, Guangzhou, Guangdong, China.
authors: Wei-Jie
authors: WJ
authors: Guan
authors: Jin-Ping
authors: JP
authors: Zheng
authors: Xu
authors: X
authors: Shi
authors: Yan-Qing
authors: YQ
authors: Xie
authors: Cai-Yu
authors: CY
authors: Jiang
authors: Yi
authors: Y
authors: Gao
authors: Zheng
authors: Z
authors: Zhu
authors: Jia-Ying
authors: JY
authors: An
authors: Xin-Xin
authors: XX
authors: Yu
authors: Wen-Ting
authors: WT
authors: Liu
mesh_terms: D000328:Adult; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology*; D001985:Bronchial Provocation Tests / Q000379:methods*; D016084:Bronchoconstriction / Q000187:drug effects; D001993:Bronchodilator Agents; D002681:China; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D017998:Leukotriene D4; D008168:Lung / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D011237:Predictive Value of Tests; D014797:Vital Capacity
chemical_list: D018927:Anti-Asthmatic Agents; D001993:Bronchodilator Agents; D016210:Methacholine Chloride; D017998:Leukotriene D4