title: Does the presence of connective tissue disease modify survival in patients with pulmonary fibrosis?
abstract: OBJECTIVE
  Previous studies into the survival differences between individuals with idiopathic pulmonary fibrosis and those with connective tissue disease associated pulmonary fibrosis (CTD-PF) have yielded mixed results. The aim of this study is to compare the survival of individuals with CTD-PF to those with idiopathic pulmonary fibrosis clinical syndrome (IPF-CS) using data derived from The Health Improvement network, a large primary care database in the UK.
  
  
  METHODS
  Incident cases of CTD-PF and IPF-CS between the years 2000-2009 were identified. Survival analysis was performed using Kaplan-Meier methods, stratified by type of connective tissue disease. Cox regression was then used to compare mortality rates between the groups, adjusting for age, gender and year of diagnosis.
  
  
  RESULTS
  A total of 324 cases of CTD-PF and 2209 cases of IPF-CS were followed up over a mean period of 2.3 years. During this period, 113 (34.9%) cases of CTD-PF and 1073 (48.6%) cases of IPF-CS died. The mortality rates for cases with CTD-PF and IPF-CS were 123.6 per 1000 person years (95%CI: 102.8-148.9) and 229.8 per 1000 person years (95% CI: 216.4-244.0) respectively. After adjusting for age, sex and year of diagnosis, cases with CTD-PF had a better prognosis compared to those with IPF-CS (HR 0.76,95%CI: 0.62-0.92).
  
  
  CONCLUSIONS
  The prognosis of individuals with CTD-PF appears to be significantly better than those with IPF-CS, but remains an important cause of death in patients with connective tissue disease, and requires more effective treatment options.
authors.affiliation: Division of Epidemiology and Public Health, University of Nottingham, Hucknall Road, Nottingham NG5 1PB, UK. Vidya.navaratnam@nottingham.ac.uk
authors.forename: V
authors.initials: V
authors.lastname: Navaratnam
authors.forename: N
authors.initials: N
authors.lastname: Ali
authors.forename: C J P
authors.initials: CJ
authors.lastname: Smith
authors.forename: T
authors.initials: T
authors.lastname: McKeever
authors.forename: A
authors.initials: A
authors.lastname: Fogarty
authors.forename: R B
authors.initials: RB
authors.lastname: Hubbard
mesh_terms: D000368:Aged; D003240:Connective Tissue Diseases / Q000150:complications* / Q000401:mortality* / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D011658:Pulmonary Fibrosis / Q000150:complications* / Q000401:mortality* / Q000473:pathology; D006113:United Kingdom / Q000453:epidemiology