title: A cohort study following up on a randomised controlled trial of a telemedicine application in COPD patients.
abstract: BACKGROUND
  The studies that constitute the knowledge base of evidence based medicine represent only 5%-50% of patients seen in routine clinical practice. Therefore, whether the available evidence applies to the implementation of a particular service often remains unclear. Chronic obstructive pulmonary disease (COPD) is no exception.
  
  
  METHODS
  In this article, the effects of implementing a telemedicine intervention for COPD patients were analysed using data collected before, during, and after a randomised controlled trial (RCT).More specifically, regression techniques using robust variance estimators were used to analyse whether the use of telemedicine, patient age, and gender could explain the risk of readmission, length of hospital admission, and death during a five-year observation period.
  
  
  RESULTS
  Increased risk of readmission was significantly related to both use of telemedicine and increased age in three sub-periods of the study, whereas women showed a more pronounced risk of readmission than men only during and after the RCT period. The number of days admitted to hospital was higher for patients using telemedicine and being of older age. Risk of death during the observation period was decreased for patients using telemedicine and for female patients and increased for elderly patients. No interaction between intervention and time period was observed.Statistically significant relationships were identified between use of telemedicine and risk of readmission, days admitted to hospital, and death.
  
  
  CONCLUSIONS
  Research on effect modification in telemedicine is essential in designing future implementation of interventions as it cannot be taken for granted that effectiveness follows from efficacy.
authors.affiliation: Centre for Innovative Medical Technologies, Odense University Hospital and University of Southern Denmark akd@rsyd.dk.
authors.forename: Anne-Kirstine
authors.initials: AK
authors.lastname: Dyrvig
authors.affiliation: Centre of Health Economics Research (COHERE), Department of Nuclear Medicine, Odense University Hospital, University of Southern Denmark.
authors.forename: Oke
authors.initials: O
authors.lastname: Gerke
authors.affiliation: Centre for Innovative Medical Technologies, Odense University Hospital and University of Southern Denmark Department for Quality, Research and HTA, Odense University Hospital.
authors.forename: Kristian
authors.initials: K
authors.lastname: Kidholm
authors.affiliation: Centre of Health Economics Research (COHERE), Department of Nuclear Medicine, Odense University Hospital, University of Southern Denmark Center for applied services research and technology assessment, University of Southern Denmark Department of Health, Technology and Services Research (HTSR), University of Twente, Enschede, the Netherlands.
authors.forename: Hindrik
authors.initials: H
authors.lastname: Vondeling
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008875:Middle Aged; D010359:Patient Readmission / Q000706:statistics & numerical data; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality / Q000628:therapy*; D012044:Regression Analysis; D017216:Telemedicine / Q000379:methods*
keywords: External validity; effectiveness; efficacy; evidence based practice; telemedicine