title: Sputum and pulmonary function in asthma.
abstract: OBJECTIVE
  To assess the relevance of sputum production to pulmonary function, in particular, persistent obstruction in patients with a primary clinical diagnosis of asthma.
  
  
  METHODS
  Cross-sectional study of all patients currently followed up in secondary care in a defined locality.
  
  
  METHODS
  National Health Service and private clinics in north-east England.
  
  
  METHODS
  All attenders, aged 18 years or older, with asthma, confirmed by reversibility of peak expiratory flow (PEF) by > or =15% and to > or =200 L/min.
  
  
  METHODS
  Pro forma history. Pulmonary function at attendance. Assessment of best function according to protocol. Measurement of actual FEV1, FVC, and PEF at attendance.
  
  
  RESULTS
  We studied 772 subjects; 387 (50%) were male; mean age was 55 years; atopic, 51%; current smokers, 11.5%; ex-smokers, 36%; and never smokers, 52.5%. Best pulmonary function was lower in chronic sputum producers (PEF, 83.2 vs 95.8; FVC, 67.9 vs 81.7% predicted). Chronic sputum production and its negative relationship with best function was strongly associated with smoking. There was little relationship between chronic sputum and persistent obstruction in nonsmokers. There were no univariate associations between sputum during attacks, or its color, and pulmonary function, but after allowing for demographic factors, including smoking, green sputum was associated with persistent obstruction. There was little relationship between sputum and actual/best function at attendance.
  
  
  CONCLUSIONS
  Chronic sputum production is associated with persistent obstruction principally in those who have smoked, suggesting that the association reflects smoking rather than asthma. There is no interaction with atopy. After allowance for cigarette smoking, there is an association between green sputum production during exacerbations and persistent obstruction. Green sputum during relapse in asthma may indicate inflammation that is relevant to prognosis.
authors.affiliation: Memorial Hospital, University of Newcastle upon Tyne.
authors.forename: C K
authors.initials: CK
authors.lastname: Connolly
authors.forename: N K
authors.initials: NK
authors.lastname: Murthy
authors.forename: S M
authors.initials: SM
authors.lastname: Alcock
authors.forename: R J
authors.initials: RJ
authors.lastname: Prescott
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000402:Airway Obstruction / Q000503:physiopathology; D000704:Analysis of Variance; D001249:Asthma / Q000503:physiopathology*; D015331:Cohort Studies; D003116:Color; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000503:physiopathology; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D011014:Pneumonia / Q000503:physiopathology; D011379:Prognosis; D012008:Recurrence; D012737:Sex Factors; D012907:Smoking / Q000503:physiopathology; D013183:Sputum / Q000378:metabolism*; D013492:Suppuration; D014797:Vital Capacity / Q000502:physiology