title: Non specific pattern of lung function in a respiratory physiology unit: causes and prevalence: results of an observational cross-sectional and longitudinal study.
abstract: BACKGROUND
  ATS/ERS Task Force has highlighted that special attention must be paid when FEV1 and FVC are concomitantly decreased (<5th percentile) and the FEV1/FVC ratio is normal (>5th percentile) because a possible cause of this non specific pattern (NSP) is collapse of small airways with normal TLC measured by body plethysmography (>5th percentile). Our objectives were to determine the main lung diseases associated with this pattern recorded prospectively in a lung function testing (LFT) unit, the prevalence of this pattern in our LFT and among the diseases identified, and its development.
  
  
  METHODS
  Observational study of routinely collected data selected from our Clinical Database Warehouse.
  
  
  RESULTS
  The prevalence of NSP was 841/12 775 tests (6.6%, 95% CI: 6.2 to 7.0%). NSP was mainly associated with seven lung diseases: asthma (prevalence of NSP among asthmatics: 12.6%), COPD/emphysema (prevalence 8.6%), bronchiectasis (12.8%), sarcoidosis (10.7%), interstitial pneumonia (4.0%), pulmonary hypertension (8.9%) and bilateral lung transplantation for cystic fibrosis (36.0%). LFT measurements were described in 185 patients with NSP and indisputable nonoverlapping causes. A moderate defect (FEV1: 66 ± 9% predicted) with mild lung hyperinflation (FRC: 111 ± 27%, RV: 131 ± 33% predicted: suggesting distal airway obstruction) was evidenced whatever the underlying cause. A long term stability of NSP was evidenced in 130/185 patients (70% 95% CI: 64 to 77%).
  
  
  CONCLUSIONS
  NSP is observed in asthma, COPD/emphysema, bronchiectasis, sarcoidosis, pulmonary hypertension, interstitial pneumonia and after bilateral lung transplantation and remains stable in the majority of patients.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Chevalier-Bidaud
authors.forename: Karine
authors.initials: K
authors.lastname: Gillet-Juvin
authors.forename: Etienne
authors.initials: E
authors.lastname: Callens
authors.forename: Romain
authors.initials: R
authors.lastname: Chenu
authors.forename: Sémia
authors.initials: S
authors.lastname: Graba
authors.forename: Mohamed
authors.initials: M
authors.lastname: Essalhi
authors.affiliation: AP-HP, Hôpital européen Georges-Pompidou, Service de Physiologie - Clinique de la Dyspnée, 75015 Paris, France. christophe.delclaux@egp.aphp.fr.
authors.forename: Christophe
authors.initials: C
authors.lastname: Delclaux
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000503:physiopathology; D001987:Bronchiectasis / Q000503:physiopathology; D003430:Cross-Sectional Studies; D003550:Cystic Fibrosis / Q000503:physiopathology / Q000601:surgery; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology; D008137:Longitudinal Studies; D008171:Lung Diseases / Q000503:physiopathology*; D017563:Lung Diseases, Interstitial / Q000503:physiopathology; D016040:Lung Transplantation; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000503:physiopathology; D017565:Sarcoidosis, Pulmonary / Q000503:physiopathology; D014109:Total Lung Capacity; D014797:Vital Capacity