title: Conditions associated with an abnormal nonspecific pattern of pulmonary function tests.
abstract: BACKGROUND
  Little is known about a fairly frequent abnormal pattern of pulmonary function test results: reduced FEV(1) and FVC with a normal FEV(1)/FVC and normal total lung capacity. We term this a nonspecific pattern (NSP). We sought to identify medical conditions having this pattern and to explore mechanisms producing it.
  
  
  METHODS
  From a database of 80,929 test results, the NSP was found in 7,702 subjects from whom was drawn a random sample of 100 subjects. Medical records and all available tests were examined.
  
  
  RESULTS
  Airway hyperresponsiveness (AHR) and obesity were common. Two groups of subjects were identified. Group A consisted of 68 subjects with evidence of airway disease, including AHR and chronic lung disease. A volume derecruitment model was proposed to explain their NSP. Group B consisted of 32 subjects with no evidence of airway disease. Restricted expansion of the thorax or lung may explain the NSP in most of these subjects. Forty subjects had repeated tests, and in only 17 were the test results consistently nonspecific.
  
  
  CONCLUSIONS
  In a random sample of 100 subjects with the NSP, the probable underlying cause of the pattern in 68 subjects was airway disease. In most of the remaining 32 subjects, restricted expansion of the thorax or lung may be implicated.
authors.affiliation: Department of Internal Medicine, College of Medicine, Mayo Clinic, Rochester, MN. Electronic address: hyatt.robert@mayo.edu.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hyatt
authors.affiliation: Department of Internal Medicine, College of Medicine, Mayo Clinic, Rochester, MN.
authors.forename: Clayton T
authors.initials: CT
authors.lastname: Cowl
authors.affiliation: Department of Internal Medicine, College of Medicine, Mayo Clinic, Rochester, MN.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Bjoraker
authors.affiliation: Department of Internal Medicine, College of Medicine, Mayo Clinic, Rochester, MN.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Scanlon
mesh_terms: D000368:Aged; D000403:Airway Resistance; D015992:Body Mass Index; D016535:Bronchial Hyperreactivity / Q000175:diagnosis / Q000453:epidemiology*; D016022:Case-Control Studies; D015897:Comorbidity; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D015994:Incidence; D008171:Lung Diseases / Q000175:diagnosis* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology*; D011336:Probability; D012123:Pulmonary Ventilation / Q000502:physiology; D012016:Reference Values; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013147:Spirometry / Q000379:methods; D014797:Vital Capacity