title: Placebo effect model in asthma clinical studies: longitudinal meta-analysis of forced expiratory volume in 1 second.
abstract: OBJECTIVE
  Our objective was to describe the time course of the placebo effect in asthma and quantitatively investigate the affective factors of the placebo effect for the placebo response simulation during the asthma clinical study design.
  
  
  METHODS
  We conducted a systemic search of public data sources for the study-level forced expiratory volume in 1 second (FEV(1)) to build the placebo effect model for studies by oral or inhaled administrations simultaneously. The administration routes, types of inhalation device, mean patient age, mean male proportion, baseline FEV(1), disease severity, year of publication, inhaled corticosteroid status during the treatment, and dropout rate were tested as covariates.
  
  
  RESULTS
  There are 34 literature sources containing 178 mean values for FEV(1) presenting the individual observations from about 3,703 patients. The exponential models adequately described the time course of placebo effect with the typical value of the maximum placebo effect (P(max)) of 0.060 L. Dropout rate incorporated in the residual error model and the disease severity (mild to moderate and moderate to severe) at baseline were covariates that remained in the final model.
  
  
  CONCLUSIONS
  The placebo effect is adequately described by an exponential model over time. By incorporating the dropout rate in the residual error model, the estimation precision was improved. The model could predict the placebo response profile in mild to severe asthmatic patients for the asthma clinical study design and could also be a structure model of the placebo effect for the pure drug effect evaluation in the asthma clinical trials.
authors.affiliation: The State Key Laboratory of Natural and Biomimetic Drugs, Peking University, 38 Xueyuan Road, Haidian District, Beijing 100191, People's Republic of China.
authors.forename: Xipei
authors.initials: X
authors.lastname: Wang
authors.forename: Dewei
authors.initials: D
authors.lastname: Shang
authors.forename: Jakob
authors.initials: J
authors.lastname: Ribbing
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Ren
authors.forename: Chenhui
authors.initials: C
authors.lastname: Deng
authors.forename: Tianyan
authors.initials: T
authors.lastname: Zhou
authors.forename: Feng
authors.initials: F
authors.lastname: Guo
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
mesh_terms: D000280:Administration, Inhalation; D000284:Administration, Oral; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage; D000328:Adult; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009330:Nebulizers and Vaporizers; D010352:Patient Dropouts; D015990:Placebo Effect; D016032:Randomized Controlled Trials as Topic / Q000379:methods*; D012129:Respiratory Function Tests / Q000379:methods
chemical_list: D000305:Adrenal Cortex Hormones