title: Forced expiratory flow between 25% and 75% of vital capacity and FEV1/forced vital capacity ratio in relation to clinical and physiological parameters in asthmatic children with normal FEV1 values.
abstract: BACKGROUND
  The assumption that the assessment of forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) does not provide additional information in asthmatic children with normal FEV(1) percent predicted has not been adequately tested.
  
  
  OBJECTIVE
  We sought to determine whether the measurement of FEF(25-75) percent predicted offers advantages over FEV(1) percent predicted and FEV(1)/forced vital capacity (FVC) percent predicted for the evaluation of childhood asthma.
  
  
  METHODS
  This is a secondary analysis of data from the Pediatric Asthma Controller Trial and the Characterizing the Response to a Leukotriene Receptor Antagonist and Inhaled Corticosteroid trials. Pearson correlation coefficients, Pearson partial correlation coefficients, canonical correlations, and receiver operating characteristic (ROC) curves were constructed.
  
  
  RESULTS
  Among 437 children with normal FEV(1) percent predicted, FEF(25-75) percent predicted, and FEV(1)/FVC percent predicted were (1) positively correlated with log(2) methacholine PC(20), (2) positively correlated with morning and evening peak expiratory flow percent predicted, and (3) negatively correlated with log(10) fraction of exhaled nitric oxide and bronchodilator responsiveness. Pearson partial correlations and canonical correlations indicated that FEF(25-75) percent predicted was better correlated with bronchodilator responsiveness and log(2) methacholine PC(20) than were FEV(1) percent predicted or FEV(1)/FVC percent predicted. In the ROC curve analysis, FEF(25-75) at 65% of predicted value had a 90% sensitivity and a 67% specificity for detecting a 20% increase in FEV(1) after albuterol inhalation.
  
  
  CONCLUSIONS
  FEF(25-75) percent predicted was well correlated with bronchodilator responsiveness in asthmatic children with normal FEV(1). FEF(25-75) percent predicted should be evaluated in clinical studies of asthma in children and might be of use in predicting the presence of clinically relevant reversible airflow obstruction.
authors.affiliation: Division of Allergy and Clinical Immunology, William Beaumont Hospital, Royal Oak, Mich, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Simon
authors.forename: Vernon M
authors.initials: VM
authors.lastname: Chinchilli
authors.forename: Brenda R
authors.initials: BR
authors.lastname: Phillips
authors.forename: Christine A
authors.initials: CA
authors.lastname: Sorkness
authors.forename: Robert F
authors.initials: RF
authors.lastname: Lemanske
authors.forename: Stanley J
authors.initials: SJ
authors.lastname: Szefler
authors.forename: Lynn
authors.initials: L
authors.lastname: Taussig
authors.forename: Leonard B
authors.initials: LB
authors.lastname: Bacharier
authors.forename: Wayne
authors.initials: W
authors.lastname: Morgan
mesh_terms: D001249:Asthma / Q000503:physiopathology; D002648:Child; D005541:Forced Expiratory Volume; D006801:Humans; D012372:ROC Curve; D012015:Reference Standards; D014797:Vital Capacity